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研究者情報

マスター

アカウント（マスター）

  • 氏名

    石川　正純(イシカワ　マサヨリ), イシカワ　マサヨリ

所属（マスター）

  • 保健科学研究院　保健科学部門　医用生体理工学分野

所属（マスター）

  • 保健科学研究院　保健科学部門　医用生体理工学分野

独自項目

syllabus

  • 2021, 治療医学物理工学, Physics and Engineering for Radiation Therapy, 修士課程, 医理工学院, 放射線治療装置、治療計画装置、放射線計測、医学物理学
  • 2021, 総合医理工学研究Ⅰ, General Research on Biomedical Science and Engineering I, 修士課程, 医理工学院, 放射線治療、放射線の医療応用、放射線計測、医学物理学
  • 2021, 総合医理工学研究Ⅱ, General Research on Biomedical Science and Engineering II, 修士課程, 医理工学院, 放射線治療、放射線の医療応用、放射線計測、医学物理学
  • 2021, 基礎放射線治療物理学, Basic Physics for Radiation Therapy, 修士課程, 医理工学院, 放射線治療、放射線物理学、加速器
  • 2021, 医療機器開発特論, Research and Development of Medical Devices, 修士課程, 医理工学院, 医療機器、医学物理、画像診断、機能診断、放射線治療、粒子線治療
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, radiation treatment, particle therapy, medical physics, radiobiology, radiomics
  • 2021, Medical Physics School, Medical Physics School, 修士課程, 医理工学院, radiation treatment, particle therapy, medical physics, radiobiology, radiomics
  • 2021, 先端医理工学研究Ⅰ, Advanced Research on Biomedical Science and Engineering I, 博士後期課程, 医理工学院, 放射線治療、放射線の医療応用、放射線計測、医学物理学
  • 2021, 先端医理工学研究Ⅱ, Advanced Research on Biomedical Science and Engineering II, 博士後期課程, 医理工学院, 放射線治療、放射線の医療応用、放射線計測、医学物理学
  • 2021, 臨床医学物理学実習（品質管理）, Clinical Medical Physics Training (Quality Assurance), 博士後期課程, 医理工学院, 放射線防護、放射線治療装置、位置照合装置、治療計画、QA Radiation protection, exteranal beam treatment units, position matching device, treatment planning system, QA
  • 2021, 放射線治療工学概論, Introduction to Radiation Therapy Equipment, 学士課程, 医学部, 放射線治療装置、外部放射線治療装置、密封小線源治療装置、治療計画装置、放射線計測機器、アクセプタンス・コミッショニング、QA/QC
  • 2021, 放射線計測学Ⅰ, Radiation Detection and DosimetryⅠ, 学士課程, 医学部, ポアソン分布、標準誤差、放射能測定、ガス入り計数管、比例計数管、GM計数管、シンチレーションカウンタ、半導体検出器、照射線量、吸収線量
  • 2021, 放射線計測学Ⅱ, Radiation Detection and Dosimetry Ⅱ, 学士課程, 医学部, 吸収線量、空洞理論、外部照射線量測定、被曝線量と防護
  • 2021, 放射線治療技術学, Radiation Therapy Technology, 学士課程, 医学部, 腫瘍、放射線感受性、処方、有害事象、放射線治療装置、外部放射線治療装置、密封小線源治療装置、治療計画装置、品質管理、放射線計測
  • 2021, 放射線計測学実習, Practice in Radiation Detection and Dosimetry, 学士課程, 医学部, ＧＭ計数装置、ポアソン分布、電離箱線量計、マルチチャネル波高分析器、比例計数管、サーベイメータ、標準計測法、半価層
  • 2021, 基礎放射線治療技術学実習, Practice in Radiation Therapy Technology, 学士課程, 医学部, 放射線治療、吸収線量測定法、放射線治療装置の精度管理、治療計画法

PositionHistory

  • 大学院医理工学院副学院長, 2022年4月1日, 2024年3月31日

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プロフィール情報

学位

  • 博士（エネルギー科学）（京都大学）

プロフィール情報

  • プロフィール

    1. 放射線医学における先進医学物理工学
    (Advanced medical engineering and physics in radiation medicine)
    2. 放射線治療計測学
    (Absorbed dose measurement in radiotherapy)
    3. 診断放射線計測学
    (Radiation measurement in radiology)
    4. 放射線治療における精度管理に関する研究
    (Quality assurance and quality control (QA/QC) in radiotherapy)

    放射線計測学、医学物理学に関して、「臨床で役立つ研究開発」をモットーに研究をしています。放射線計測、特に放射線治療分野・診断分野における計測のエキスパートになりたいと思っている学生は、私の研究室を訪問してみてください。

  • 姓

    石川, イシカワ

  • 名

    正純, マサヨリ

  • ID各種

    201301025528526393

対象リソース

業績リスト

研究キーワード

  • 吸収線量評価   SOF検出器   リアルタイムモニタ   熱中性子検出器   中性子捕捉療法   密封小線源治療   超小型線量計   放射線治療学   ホウ素中性子捕捉療法   コリメータシステム   中性子捕捉両方   線量計開発   PG-SPECT   体内線量測定   放射線障害予防   in vivo dosimetry   中性子補足療法   リアルタイム線量測定   リアルタイム線量評価   放射線治療   体幹部定位放射線照射   プラスチック検出器   ピンホールコリメータ   加速器   電子線トラック解析   非線形最適化   モンテカルロ法   量子線シミュレーション   生物発光   生物影響   

研究分野

  • ライフサイエンス / 放射線科学
  • 環境・農学 / 化学物質影響
  • 環境・農学 / 放射線影響

経歴

  • 2015年04月 - 現在 北海道大学 保健科学研究院 教授
  • 2010年05月 - 2015年03月 北海道大学 大学院医学研究科 教授
  • 2008年04月 - 2010年04月 北海道大学 大学院医学研究科 准教授
  • 2006年04月 - 2008年03月 北海道大学病院 分子追跡放射線医療寄附研究部門 特任助教授
  • 2005年04月 - 2006年03月 東京大学 工学系研究科原子力国際専攻 助手
  • 2003年04月 - 2005年03月 東京大学 原子力研究総合センター 助手
  • 1999年07月 - 2003年03月 広島大学 原爆放射能医学研究所 助手

学歴

  • 1998年04月 - 1999年06月   京都大学   エネルギー科学研究科
  • 1996年04月 - 1998年03月   京都大学   エネルギー科学研究科
  • 1992年04月 - 1996年03月   京都大学   工学部   金属系学科

受賞

  • 2019年11月 一般社団法人日本癌学会 第9回 JCA-CHAAO賞
     動体追跡技術と同期照射技術を用いた高精度放射線治療の開発と臨床研究 
    受賞者: 白土 博樹;清水 伸一;鬼丸 力也;品川 尚文;阿保 大介;加藤 徳雄;梅垣 菊男;石川 正純;宮本 直樹;青山 英史
  • 2018年04月 日本医学物理学会 英語プレゼンテーション賞
     Fundamental study on dosimetric error due to phantom setup error for film-based dose distribution analysis 
    受賞者: 石川正純
  • 2017年11月 日本放射線腫瘍学会 優秀査読者賞
     
    受賞者: 石川正純
  • 2017年07月 北海道大学大学院保健科学研究院 優秀論文賞
     
    受賞者: 石川正純
  • 2016年02月 北海道大学 北海道大学総長賞（研究奨励賞）
     
    受賞者: 石川正純
  • 2015年03月 北海道大学 北海道大学総長賞（研究奨励賞）
     
    受賞者: 石川正純
  • 2015年02月 北海道庁 北海道科学技術奨励賞
     
    受賞者: 石川正純
  • 2014年12月 日本放射線腫瘍学会 第27回学術大会 優秀演題賞
     
    受賞者: 石川正純
  • 2014年09月 7th Korea-Japan Joint Meeting on Medical Physics Oral Presentation Award
     
    受賞者: 石川正純
  • 2014年09月 7th Korea-Japan Joint Meeting on Medical Physics Poster Presentation Award
     
    受賞者: 石川正純
  • 2013年03月 北海道大学大学院医学研究科・医学部医学科 優秀研究賞
     
    受賞者: 石川正純
  • 2012年04月 日本医学物理学会 第103回学術大会 大会長賞
     
    受賞者: 石川正純
  • 2011年11月 日本放射線腫瘍学会 第24回学術大会 優秀演題賞
     
    受賞者: 石川正純
  • 2008年04月 日本医学物理学会 第95回学術大会 大会長賞
     
    受賞者: 石川正純
  • 2007年04月 日本医学物理学会 第11回論文賞
     
    受賞者: 石川正純
  • 2006年11月 日本放射線腫瘍学会 第19回学術大会優秀発表賞
     
    受賞者: 石川正純

論文

  • Yusuke Matsuya, Tatsuhiko Sato, Tamon Kusumoto, Yoshie Yachi, Ryosuke Seino, Misako Miwa, Masayori Ishikawa, Shigeo Matsuyama, Hisanori Fukunaga
    Scientific Reports 14 1 2024年07月19日 
    Abstract Boron neutron capture therapy (BNCT) is a unique radiotherapy of selectively eradicating tumor cells using boron compounds (e.g., 4-borono-l-phenylalanine [BPA]) that are heterogeneously taken up at the cellular level. Such heterogenicity potentially reduces the curative efficiency. However, the effects of temporospatial heterogenicity on cell killing remain unclear. With the technical combination of radiation track detector and biophysical simulations, this study revealed the cell cycle-dependent heterogenicity of BPA uptake and subsequent biological effects of BNCT on HeLa cells expressing fluorescent ubiquitination-based cell cycle indicators, as well as the modification effects of polyvinyl alcohol (PVA). The results showed that the BPA concentration in the S/G2/M phase was higher than that in the G1/S phase and that PVA enhances the biological effects both by improving the uptake and by canceling the heterogenicity. These findings might contribute to a maximization of therapeutic efficacy when BNCT is combined with PVA and/or cell cycle-specific anticancer agents.
  • Hamada T, Sutherland K, Ishikawa M, Saito J, Miyamoto N, Honma S, Shirato H, Honma K-I
    Biochemical and Biophysical Research Communications 2024年07月 [査読有り][通常論文]
  • Minoru Nakao, Shuichi Ozawa, Hideharu Miura, Kiyoshi Yamada, Masahiro Hayata, Kosuke Hayashi, Daisuke Kawahara, Takeo Nakashima, Yusuke Ochi, Takuro Okumura, Haruhide Kunimoto, Atsushi Kawakubo, Hayate Kusaba, Hiroshige Nozaki, Kosaku Habara, Naoki Tohyama, Teiji Nishio, Mitsuhiro Nakamura, Toshiyuki Minemura, Hiroyuki Okamoto, Masayori Ishikawa, Masahiko Kurooka, Hidetoshi Shimizu, Kenji Hotta, Masahide Saito, Masahiro Nakano, Masato Tsuneda, Yasushi Nagata
    Medical physics 51 3 1571 - 1582 2024年03月 
    BACKGROUND: Inadequate computed tomography (CT) number calibration curves affect dose calculation accuracy. Although CT number calibration curves registered in treatment planning systems (TPSs) should be consistent with human tissues, it is unclear whether adequate CT number calibration is performed because CT number calibration curves have not been assessed for various types of CT number calibration phantoms and TPSs. PURPOSE: The purpose of this study was to investigate CT number calibration curves for mass density (ρ) and relative electron density (ρe ). METHODS: A CT number calibration audit phantom was sent to 24 Japanese photon therapy institutes from the evaluating institute and scanned using their individual clinical CT scan protocols. The CT images of the audit phantom and institute-specific CT number calibration curves were submitted to the evaluating institute for analyzing the calibration curves registered in the TPSs at the participating institutes. The institute-specific CT number calibration curves were created using commercial phantom (Gammex, Gammex Inc., Middleton, WI, USA) or CIRS phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA)). At the evaluating institute, theoretical CT number calibration curves were created using a stoichiometric CT number calibration method based on the CT image, and the institute-specific CT number calibration curves were compared with the theoretical calibration curve. Differences in ρ and ρe over the multiple points on the curve (Δρm and Δρe,m , respectively) were calculated for each CT number, categorized for each phantom vendor and TPS, and evaluated for three tissue types: lung, soft tissues, and bones. In particular, the CT-ρ calibration curves for Tomotherapy TPSs (ACCURAY, Sunnyvale, CA, USA) were categorized separately from the Gammex CT-ρ calibration curves because the available tissue-equivalent materials (TEMs) were limited by the manufacturer recommendations. In addition, the differences in ρ and ρe for the specific TEMs (ΔρTEM and Δρe,TEM , respectively) were calculated by subtracting the ρ or ρe of the TEMs from the theoretical CT-ρ or CT-ρe calibration curve. RESULTS: The mean ± standard deviation (SD) of Δρm and Δρe,m for the Gammex phantom were -1.1 ± 1.2 g/cm3 and -0.2 ± 1.1, -0.3 ± 0.9 g/cm3 and 0.8 ± 1.3, and -0.9 ± 1.3 g/cm3 and 1.0 ± 1.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm and Δρe,m for the CIRS phantom were 0.3 ± 0.8 g/cm3 and 0.9 ± 0.9, 0.6 ± 0.6 g/cm3 and 1.4 ± 0.8, and 0.2 ± 0.5 g/cm3 and 1.6 ± 0.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm for Tomotherapy TPSs was 2.1 ± 1.4 g/cm3 for soft tissues, which is larger than those for other TPSs. The mean ± SD of Δρe,TEM for the Gammex brain phantom (BRN-SR2) was -1.8 ± 0.4, implying that the tissue equivalency of the BRN-SR2 plug was slightly inferior to that of other plugs. CONCLUSIONS: Latent deviations between human tissues and TEMs were found by comparing the CT number calibration curves of the various institutes.
  • Hideki Kojima, Masayori Ishikawa, Makoto Takigami
    Medical physics 50 11 7281 - 7293 2023年11月 
    BACKGROUND: Although flattening filter free (FFF) beams are commonly used in clinical treatment, the accuracy of dose measurements in FFF beams has been questioned. Higher dose per pulse (DPP) such as FFF beams from a linear accelerator may cause problems in dose profile measurements using an ionization chamber due to the change of the charge collection efficiency. Ionization chambers are commonly used for percent depth dose (PDD) measurements. Changes of DPP due to chamber movement during PDD measurement can vary the ion collection efficiency of ionization chambers. In the case of FF beams, the DPP fluctuation is negligible, but in the case of the FFF beams, the DPP is 2.5 ∼ 4 times larger than that of the FF beam, and the change in ion collection efficiency is larger than that of the FF beam. PDD profile normalized by maximum dose depth, 10 cm depth for example, may therefore be affected by the ion collection efficiency. PURPOSE: In this study, we investigate the characteristics of the ion collection efficiency change depending on the DPP of each ionization chamber in the FFF beam. We furthermore propose a method to obtain the chamber- independent PDD by applying a DPP-dependent ion recombination correction. METHODS: Prior to investigating the relationship between DPP and charge collection efficiency, Jaffe-plots were generated with different DPP settings to investigate the linearity between the applied voltage and collected charge. The absolute dose measurement using eight ionization chambers under the irradiation settings of 0.148, 0.087, and 0.008 cGy/pulse were performed. Applied voltages for the Jaffe-plots were 100, 125, 150, 200, 250, and 300 V. The ion recombination correction factor Pion was calculated by the two-voltage analysis (TVA) method at the applied voltages of 300 and 100 V. The DPP dependency of the charge collection efficiency for each ionization chamber were evaluated from the DPP- Pion plot. PDD profiles for the 10 MV FFF beam were measured using Farmer type chambers (TN30013, FC65-P, and FC65-G) and mini-type chambers (TN31010, TN31021, CC13, CC04, and FC23-C). The PDD profiles were corrected with ion recombination correction at negative and positive polar applied voltages of 100 and 300 V. RESULTS: From the DPP-Pion relation for each ionization chamber with DPP ranging from 0.008 cGy/pulse to 0.148 cGy/pulse, all Farmer and mini-type chambers satisfied the requirements described in AAPM TG-51 addendum. However, Pion for the CC13 was most affected by DPP among tested chambers. The maximum deviation among PDDs using eight ionization chambers for 10 MV FFF was about 1%, but the deviation was suppressed to about 0.5% by applying ion recombination correction at each depth. CONCLUSIONS: In this study, the deviation of PDD profile among the ionization chambers was reduced by the ion recombination coefficient including the DPP dependency, especially for high DPP beams such as FFF beams. The present method is particularly effective for CC13, where the ion collection efficiency is highly DPP dependent.
  • Mitsuhiro Nakamura, Dejun Zhou, Toshiyuki Minemura, Satoshi Kito, Hiroyuki Okamoto, Naoki Tohyama, Masahiko Kurooka, Yu Kumazaki, Masayori Ishikawa, Catharine H Clark, Elizabeth Miles, Joerg Lehmann, Nicolaus Andratschke, Stephen Kry, Satoshi Ishikura, Takashi Mizowaki, Teiji Nishio
    Journal of applied clinical medical physics 24 6 e14040  2023年06月 
    PURPOSE: The Medical Physics Working Group of the Radiation Therapy Study Group at the Japan Clinical Oncology Group is currently developing a virtual audit system for intensity-modulated radiation therapy dosimetry credentialing. The target dosimeters include films and array detectors, such as ArcCHECK (Sun Nuclear Corporation, Melbourne, Florida, USA) and Delta4 (ScandiDos, Uppsala, Sweden). This pilot study investigated the feasibility of our virtual audit system using previously acquired data. METHODS: We analyzed 46 films (32 and 14 in the axial and coronal planes, respectively) from 29 institutions. Global gamma analysis between measured and planned dose distributions used the following settings: 3%/3 mm criteria (the dose denominator was 2 Gy), 30% threshold dose, no scaling of the datasets, and 90% tolerance level. In addition, 21 datasets from nine institutions were obtained for array evaluation. Five institutions used ArcCHECK, while the others used Delta4. Global gamma analysis was performed with 3%/2 mm criteria (the dose denominator was the maximum calculated dose), 10% threshold dose, and 95% tolerance level. The film calibration and gamma analysis were conducted with in-house software developed using Python (version 3.9.2). RESULTS: The means ± standard deviations of the gamma passing rates were 99.4 ± 1.5% (range, 92.8%-100%) and 99.2 ± 1.0% (range, 97.0%-100%) in the film and array evaluations, respectively. CONCLUSION: This pilot study demonstrated the feasibility of virtual audits. The proposed virtual audit system will contribute to more efficient, cheaper, and more rapid trial credentialing than on-site and postal audits; however, the limitations should be considered when operating our virtual audit system.
  • Hiroyuki Okamoto, Naoya Murakami, Fumiaki Isohashi, Takahiro Kasamatsu, Yoko Hasumi, Hiroaki Kobayashi, Masayori Ishikawa, Mitsuhiro Nakamura, Teiji Nishio, Hiroshi Igaki, Satoshi Ishikura, Nobuo Yaegashi, Takashi Mizowaki, Yasumasa Nishimura, Takafumi Toita
    Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 183 109630 - 109630 2023年06月 
    BACKGROUND AND PURPOSE: The Japan Clinical Oncology Group (JCOG) 1402 conducted a multicenter clinical trial of postoperative intensity-modulated radiotherapy (IMRT) for high-risk uterine cervical cancer patients. We assess effectiveness of the quality assurance (QA) program in central review through dummy runs (DRs) performed before patient enrollment and post-treatment individual case review (ICR), and clarify the pitfalls in treatment planning. MATERIAL AND METHODS: The ICRs were conducted using the same QA program as the DR for 214 plans. The deviations were compared with those demonstrated in the DRs, and the pitfalls were clarified. Fifteen face-to-face meetings were held with physicians at participating institutions to provide feedback. RESULTS: Two-hundred and eighty-eight deviations and nine violations were detected in the 214 plans. The patterns of the deviations observed in the ICRs were similar to that in the DR. Frequent deviations were observed in clinical target volume (CTV) delineations, 50% in the DRs and 37% in the ICRs, respectively. In the ICRs, approximately 1.4 deviations/violations were observed per plan, which was lower than DR. Nine violations included inaccurate CTV delineation and improper PTV (planning target volume) margin, which had risks in loco-regional failures by inadequate dose coverage. CONCLUSIONS: Our developed QA program commonly used in DR and ICR clarified the pitfalls in treatment plans. Although the frequent deviations in CTV delineations were observed in the ICR, the deviations decreased compared to that in the DR. More specified face-to-face meetings with participating institutions will be necessary to maintain the quality of IMRT in the clinical protocol.
  • Kento Miyata, Ryo Ogawara, Masayori Ishikawa
    Sensors (Basel, Switzerland) 23 10 2023年05月09日 
    In positron emission tomography (PET), parallax errors degrade spatial resolution. The depth of interaction (DOI) information provides the position in the depth of the scintillator interacting with the γ-rays, thus reducing parallax errors. A previous study developed a Peak-to-Charge discrimination (PQD), which can separate spontaneous alpha decay in LaBr3:Ce. Since decay constant of GSO:Ce depends on Ce concentration, the PQD is expected to discriminate GSO:Ce scintillators with different Ce concentration. In this study, the PQD-based DOI detector system was developed, which can be processed online and implemented in PET. A detector was composed of four layers of GSO:Ce crystals and a PS-PMT. The four crystals were obtained from both the top and bottom of ingots with a nominal Ce concentration of 0.5 mol% and 1.5 mol%. The PQD was implemented on the Xilinx Zynq-7000 SoC board with 8ch Flash ADC to gain real-time processing, flexibility, and expandability. The results showed that the mean Figure of Merits in 1D between four scintillators are 1.5, 0.99, 0.91 for layers between 1st-2nd, 2nd-3rd, and 3rd-4th respectively, and the mean Error Rate in 1D between four scintillators are 3.50%, 2.96%, 13.3%, and 1.88% for layers 1, 2, 3, and 4, respectively. In addition, the introduction of the 2D PQDs resulted in the mean Figure of Merits in 2D greater than 0.9 and the mean Error Rate in 2D less than 3% in all layers.
  • Mitsuhiro Kon, Hiroyuki Okamoto, Satoshi Nakamura, Kotaro Iijima, Takahito Chiba, Mihiro Takemori, Hiroki Nakayama, Tetsu Nakaichi, Shohei Mikasa, Kyohei Fujii, Yuka Urago, Masayori Ishikawa, Toshimitsu Sofue, Shoichi Katsuta, Koji Inaba, Hiroshi Igaki, Tomohiko Aso
    Journal of radiation research 64 1 186 - 194 2023年01月20日 
    This study aimed to clarify the differences in radiotherapy dose characteristics and delivery efficiency between the supine and prone positions in patients with prostate cancer using the CyberKnife. The planning computed tomography (CT) and delineations of the prone position were obtained by rotating the supine CT images with delineations of 180° using image processing software. The optimization parameters for planning target volume (PTV) and organs at risk (OARs) were based on the prone position. The optimization parameters determined for the prone position were applied to the supine position for optimization and dose calculation. The dosimetric characteristics of the PTV and OARs, and delivery efficiency were compared between the two different patient positions. The plans in the prone position resulted in better PTV conformity index (nCI), rectum V90%, V80%, V75%, V50% and bladder V50%. A significant difference was observed in treatment time and depth along the central axis (dCAX) between the two plans. The mean treatment time per fraction and dCAX for the supine and prone positions were 20.9 ± 1.7 min versus 19.8 ± 1.3 min (P = 0.019) and 151.1 ± 33.6 mm versus 233.2 ± 8.8 mm (P < 0.001), respectively. In this study the prone position was found to improve dosimetric characteristics and delivery efficiency compared with the supine position during prostate cancer treatment with the CyberKnife.
  • Kento Miyata, Ryo Ogawara, Masayori Ishikawa
    Sensors 23 10 4584 - 4584 2023年
  • Fumihiro Sasaki, Yuusuke Yamashita, Satoshi Nakano, Masayori Ishikawa
    Journal of applied clinical medical physics 24 4 e13872  2022年12月20日 
    PURPOSE: We evaluate an SGRT device (Voxelan HEV-600 M/RMS) installed with Radixact, with the view angle of the Voxelan's camera at 74 degrees. The accuracy of Voxelan with this steep angle was evaluated with phantom experiments and inter-fractional setup errors of patients. METHODS: In the phantom experiments, the difference between the measured values of Voxelan from the truth was evaluated for translations and rotations. The inter-fractional setup error between the setup using skin markers with laser localizer (laser setup: LS) and the setup using Voxelan (surface setup: SS) was compared for head and neck (N = 19), chest (N = 7) and pelvis (N = 9) cases. The inter-fractional setup error was calculated by subtracting from bone matching by megavoltage computed tomography (MVCT) as ground truth. RESULTS: From the phantom experiments, the average difference between the measured values of Voxelan from the truth was within 1 mm and 1 degree. In all cases, inter-fractional setup error based on MVCT was not significantly different between LS and SS by Welch's t-test (P > 0.05). The vector offset of the LS for head and neck, chest, and pelvis were 6.5, 9.6, and 9.6 mm, respectively, and that of the SS were 5.8, 8.6, and 12.6 mm, respectively. Slight improvement was observed for the head and neck, and chest cases, however, pelvis cases were not improved because the umbilical region could not be clearly visualized as a reference. CONCLUSION: The results show that SS in Voxelan with an installation angle of 74 degrees is equal to or better than LS.
  • Go Chiba, Hikaru Handa, Masayori Ishikawa
    Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine 190 110465 - 110465 2022年12月 
    The quick and accurate neutron and photon transport calculations are desired in the optimization calculations for the neutron source design, and in the present work, we establish the deterministic neutron and photon transport calculation procedure with the nuclear reactor physics calculation code system CBZ. Numerical calculation conditions are carefully chosen, and the efficient and practical condition is determined. Test calculations are carried out for the simple cylindrical systems with various kinds of neutron moderators, and the results are compared with the reference solutions obtained by the continuous-energy Monte Carlo code PHITS. Generally good agreements are obtained for all the benchmark problems. In addition, another problem with the detailed geometry for the neutron source is prepared. In this realistic problem also, good agreement is obtained between CBZ and PHITS. These results demonstrate the high accuracy of CBZ in the application to the design optimization calculations for the neutron source.
  • Nakaya M, Wakamatsu M, Motegi H, Ami Tanaka A, Sutherland K, Ishikawa M, Ozaki M, Shirato H, Hamada K, Hamada T* (* Correspondence).
    Biochemistry and Biophysics Reports 32 101344 - 101344 2022年09月 [査読有り][通常論文]
     
    Clock gene expression in most organs of the living body exhibits a diurnal rhythm synchronized with the external 24 h light-dark (LD) cycle via circadian pacemaker suprachiasmatic nucleus (SCN). Disturbances in clock gene expression due to desynchronization of clock gene expression of the external LD cycle are risk factors for developing various diseases. Measuring the in vivo clock genes expression rhythm for a long duration under LD conditions can greatly contribute to understand the pathogenic mechanism of the disease caused by the disturbance of the biological rhythm. However, it is presently difficult to continuously measure gene expression for a long duration under LD conditions. In present study, we succeeded in measuring Period1 (Per1) gene expression under LD conditions using ultraviolet (UV) light with filter cut the visible light range. In addition, we succeeded in measuring the kinetic change of liver Per1 gene expression during the process of desynchronization of behavioral rhythm from the LD cycle by chronic administration of methamphetamine (MAP). In the future, by using this system to measure clock gene expression rhythms of brain tissues such as SCN and peripheral tissues under LD conditions, it could contribute to understand the onset mechanism of diseases induced by the desynchronization mechanism of biological rhythm to the LD cycle.
  • Yusuke Matsuya, Nobuyuki Hamada, Yoshie Yachi, Yukihiko Satou, Masayori Ishikawa, Hiroyuki Date, Tatsuhiko Sato
    Cancers 14 4 1045 - 1045 2022年02月18日 
    Cesium-bearing microparticles (Cs-BMPs) can reach the human respiratory system after inhalation, resulting in chronic local internal exposure. We previously investigated the spatial distribution of DNA damage induced in areas around a Cs-BMP; however, the biological impacts have not been fully clarified due to the limited amount of data. Here, we investigated the inflammatory signaling and DNA damage responses after local exposure to a Cs-BMP in vitro. We used two normal human lung cell lines, i.e., lung fibroblast cells (WI-38) and bronchial epithelial cells (HBEC3-KT). After 24 h exposure to a Cs-BMP, inflammation was evaluated by immunofluorescent staining for nuclear factor κB (NF-κB) p65 and cyclooxygenase 2 (COX-2). The number of DNA double-strand breaks (DSBs) was also detected by means of phospholylated histone H2AX (γ-H2AX) focus formation assay. Cs-BMP exposure significantly increased NF-κB p65 and COX-2 expressions, which were related to the number of γ-H2AX foci in the cell nuclei. Compared to the uniform (external) exposure to 137Cs γ-rays, NF-κB tended to be more activated in the cells proximal to the Cs-BMP, while both NF-κB p65 and COX-2 were significantly activated in the distal cells. Experiments with chemical inhibitors for NF-κB p65 and COX-2 suggested the involvement of such inflammatory responses both in the reduced radiosensitivity of the cells proximal to Cs-BMP and the enhanced radiosensitivity of the cells distal from Cs-BMP. The data show that local exposure to Cs-BMP leads to biological effects modified by the NF-κB pathway, suggesting that the radiation risk for Cs-BMP exposure can differ from that estimated based on conventional uniform exposure to normal tissues.
  • Yusuke Matsuya, Tamon Kusumoto, Yoshie Yachi, Yuho Hirata, Misako Miwa, Masayori Ishikawa, Hiroyuki Date, Yosuke Iwamoto, Shigeo Matsuyama, Hisanori Fukunaga
    AIP Advances 12 2 025013 - 025013 2022年02月01日
  • Kanako Ukon, Yohei Arai, Seishin Takao, Taeko Matsuura, Masayori Ishikawa, Hiroki Shirato, Shinichi Shimizu, Kikuo Umegaki, Naoki Miyamoto
    Journal of radiation research 62 5 926 - 933 2021年09月13日 
    The purpose of this work is to show the usefulness of a prediction method of tumor location based on partial least squares regression (PLSR) using multiple fiducial markers. The trajectory data of respiratory motion of four internal fiducial markers inserted in lungs were used for the analysis. The position of one of the four markers was assumed to be the tumor position and was predicted by other three fiducial markers. Regression coefficients for prediction of the position of the tumor-assumed marker from the fiducial markers' positions is derived by PLSR. The tracking error and the gating error were evaluated assuming two possible variations. First, the variation of the position definition of the tumor and the markers on treatment planning computed tomograhy (CT) images. Second, the intra-fractional anatomical variation which leads the distance change between the tumor and markers during the course of treatment. For comparison, rigid predictions and ordinally multiple linear regression (MLR) predictions were also evaluated. The tracking and gating errors of PLSR prediction were smaller than those of other prediction methods. Ninety-fifth percentile of tracking/gating error in all trials were 3.7/4.1 mm, respectively in PLSR prediction for superior-inferior direction. The results suggested that PLSR prediction was robust to variations, and clinically applicable accuracy could be achievable for targeting tumors.
  • Suguru Kimura, Naoki Miyamoto, Kenneth L Sutherland, Ryusuke Suzuki, Hiroki Shirato, Masayori Ishikawa
    Journal of applied clinical medical physics 22 7 165 - 176 2021年07月 
    PURPOSE: The real-time tumor tracking radiotherapy (RTRT) system requires periodic quality assurance (QA) and quality control. The goal of this study is to propose QA procedures from the viewpoint of imaging devices in the RTRT system. METHODS: Tracking by the RTRT system (equips two sets of colored image intensifiers (colored I.I.s) fluoroscopy units) for the moving gold-marker (diameter 2.0 mm) in a rotating phantom were performed under various X-ray conditions. To analyze the relationship between fluoroscopic image quality and precision of gold marker coordinate calculation, the standard deviation of the 3D coordinate (σ3D [mm]) of the gold marker, the mean of the pattern recognition score (PRS) and the standard deviation of the distance between rays (DBR) (σDBR [mm]) were evaluated. RESULTS: When tracking with speed of 10-60 mm/s, σDBR increased, though the mean PRS did not change significantly (p>0.05). On the contrary, the mean PRS increased depending on the integral noise equivalent quanta (∫NEQ) that is an indicator of image quality calculated from the modulation transfer function (MTF) as an indicator of spatial resolution and the noise power spectrum (NPS) as an indicator of noise characteristic. CONCLUSION: The indicators of NEQ, MTF, and NPS were useful for managing the tracking accuracy of the RTRT system. We propose observing the change of these indicators as additional QA procedures for each imaging device from the commissioning baseline.
  • Harumi Kanou, Kouki Nagasawa, Yuki Ishii, Aya Chishima, Juri Hayashi, Sanae Haga, Kenneth Sutherland, Masayori Ishikawa, Michitaka Ozaki, Hiroki Shirato, Kazuko Hamada, Toshiyuki Hamada
    Biochemical and biophysical research communications 560 14 - 20 2021年06月30日 
    Clock genes express circadian rhythms in most organs. These rhythms are organized throughout the whole body, regulated by the suprachiasmatic nucleus (SCN) in the brain. Disturbance of these clock gene expression rhythms is a risk factor for diseases such as obesity. In the present study, to explore the role of clock genes in developing diabetes, we examined the effect of streptozotocin (STZ)-induced high glucose on Period1 (Per1) gene expression rhythm in the liver and the olfactory bub (OB) in the brain. We found a drastic increase of Per1 expression in both tissues after STZ injection while blood glucose content was low. After a rapid expression peak, Per1 expression showed no rhythm. Associated with an increase of glucose content, behavior became arrhythmic. Finally, we succeeded in detecting an increase of Per1 expression in mice hair follicles on day 1 after STZ administration, before the onset of symptoms. These results show that elevated Per1 expression by STZ plays an important role in the aggravation of diabetes.
  • Kentaro Baba, Tamon Kusumoto, Shogo Okada, Masayori Ishikawa
    JOURNAL OF APPLIED PHYSICS 129 24 2021年06月 
    Monte Carlo track structure simulation is a powerful method for estimating damage induced by water radiolysis products for cell killing. To investigate the influence of multiple ionization for the formation of water radiolysis products under H-1(+), He-4(2+), and C-12(6+) ion beams, a Monte Carlo simulation based on Geant4-DNA was carried out. The G-value of H2O2 increased monotonically with increasing linear energy transfer up to 200 eV/nm. Above 200 eV/nm, the G-value of H2O2 began dropping, but only when the influence of multiple ionization was considered. This trend is in good agreement with the experimental results. Furthermore, we successfully reproduce the experimental results of G-values of HO2 center dot + O-2(center dot-). The role of the multiple ionization in the production of H2O2, HO2 center dot, O-2(center dot-), and O-2 is also discussed.
  • Stephen F Kry, Jessica Lye, Catharine H Clark, Nicolaus Andratschke, Alexis Dimitriadis, David Followill, Rebecca Howell, Mohammad Hussein, Masayori Ishikawa, Satoshi Kito, Tomas Kron, Jonny Lee, Jeff Michalski, Angelo Filippo Monti, Nick Reynaert, Paige Taylor, Karen Venables, Ying Xiao, Joerg Lehmann
    Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 159 106 - 111 2021年06月 
    PURPOSE: To promote consistency in clinical trials by recommending a uniform framework as it relates to radiation transport and dose calculation in water versus in medium. METHODS: The Global Quality Assurance of Radiation Therapy Clinical Trials Harmonisation Group (GHG; www.rtqaharmonization.org) compared the differences between dose to water in water (Dw,w), dose to water in medium (Dw,m), and dose to medium in medium (Dm,m). This was done based on a review of historical frameworks, existing literature and standards, clinical issues in the context of clinical trials, and the trajectory of radiation dose calculations. Based on these factors, recommendations were developed. RESULTS: No framework was found to be ideal or perfect given the history, complexity, and current status of radiation therapy. Nevertheless, based on the evidence available, the GHG established a recommendation preferring dose to medium in medium (Dm,m). CONCLUSIONS: Dose to medium in medium (Dm,m) is the preferred dose calculation and reporting framework. If an institution's planning system can only calculate dose to water in water (Dw,w), this is acceptable.
  • Yusuke Matsuya, Stephen J McMahon, Karl T Butterworth, Shingo Naijo, Isshi Nara, Yoshie Yachi, Ryo Saga, Masayori Ishikawa, Tatsuhiko Sato, Hiroyuki Date, Kevin M Prise
    Physics in medicine and biology 66 7 2021年04月06日 
    Hypoxic cancer cells within solid tumours show radio-resistance, leading to malignant progression in fractionated radiotherapy. When prescribing dose to tumours under heterogeneous oxygen pressure with intensity-modulated radiation fields, intercellular signalling could have an impact on radiosensitivity between in-field and out-of-field cells. However, the impact of hypoxia on radio-sensitivity under modulated radiation intensity remains to be fully clarified. Here, we investigate the impact of hypoxia on in-field and out-of-field radio-sensitivities using two types of cancer cells, DU145 and H1299. Using a nBIONIX hypoxic culture kit and a shielding technique to irradiate 50% of a cell culture flask, oxygen enhancement ratios (OERs) for double-strand breaks (DSB) and cell death endpoints were determined. These in vitro measurements indicate that hypoxia impacts out-of-field cells, although the hypoxic impacts on out-of-field cells for cell survival were dose-dependent and smaller compared to those for in-field and uniformly irradiated cells. These decreased radio-sensitivities of out-of-field cells were shown as a consistent tendency for both DSB and cell death endpoints, suggesting that radiation-induced intercellular communication is of importance in advanced radiotherapy dose-distributions such as with intensity-modulated radiotherapy.
  • Kanako Nakajima, Kazuko Hamada, Ryoga Ito, Yukina Yoshida, Kenneth Sutherland, Masayori Ishikawa, Michitaka Ozaki, Hiroki Shirato, Toshiyuki Hamada
    Luminescence : the journal of biological and chemical luminescence 36 1 94 - 98 2021年02月 
    Circadian disturbance of clock gene expression is a risk factor for diseases such as obesity, cancer, and sleep disorders. To study these diseases, it is necessary to monitor and analyze the expression rhythm of clock genes in the whole body for a long duration. The bioluminescent reporter enzyme firefly luciferase and its substrate d-luciferin have been used to generate optical signals from tissues in vivo with high sensitivity. However, little information is known about the stability of d-luciferin to detect gene expression in living animals for a long duration. In the present study, we examined the stability of a luciferin solution over 21 days. l-Luciferin, which is synthesized using racemization of d-luciferin, was at high concentrations after 21 days. In addition, we showed that bioluminescence of Period1 (Per1) expression in the liver was significantly decreased compared with the day 1 solution, although locomotor activity rhythm was not affected. These results showed that d-luciferin should be applied to the mouse within, at most, 7 days to detect bioluminescence of Per1 gene expression rhythm in vivo.
  • Kentaro Baba, Tamon Kusumoto, Shogo Okada, Ryo Ogawara, Satoshi Kodaira, Quentin Raffy, Rémi Barillon, Nicolas Ludwig, Catherine Galindo, Philippe Peaupardin, Masayori Ishikawa
    Scientific reports 11 1 1524 - 1524 2021年01月15日 
    We evaluate the track segment yield G' of typical water radiolysis products (eaq-, ·OH and H2O2) under heavy ions (He, C and Fe ions) using a Monte Carlo simulation code in the Geant4-DNA. Furthermore, we reproduce experimental results of ·OH of He and C ions around the Bragg peak energies (< 6 MeV/u). In the relatively high energy region (e.g., > 10 MeV/u), the simulation results using Geant4-DNA have agreed with experimental results. However, the G-values of water radiolysis species have not been properly evaluated around the Bragg peak energies, at which high ionizing density can be expected. Around the Bragg peak energy, dense continuous secondary products are generated, so that it is necessary to simulate the radical-radical reaction more accurately. To do so, we added the role of secondary products formed by irradiation. Consequently, our simulation results are in good agreement with experimental results and previous simulations not only in the high-energy region but also around the Bragg peak. Several future issues are also discussed regarding the roles of fragmentation and multi-ionization to realize more realistic simulations.
  • Ryoga Ito, Kazuko Hamada, Shigeru Kasahara, Yoshihiro Kikuchi, Kanako Nakajima, Kenneth Sutherland, Hiroki Shirato, Michitaka Ozaki, Masayori Ishikawa, Toshiyuki Hamada
    Luminescence : the journal of biological and chemical luminescence 35 8 1248 - 1253 2020年12月 
    Because the disruption of circadian clock gene is a risk factor in many diseases such as obesity and cancer, it is important to monitor and analyzed the expression of the rhythm of the clock gene throughout the body over a long period of time. Although we previously reported on a new gene expression analysis system tracking a target position on the body surface of freely moving mice, the experimental apparatus required a large space. We have therefore developed an in vivo recording system using a portable photomultiplier tube (PMT) system attached to an optical fibre. Directly connecting the target area with the device, we could easily measure the photon counts in a very small space. However, little information is known about the characteristics of optical fibres when exposed to twisting/looping in association with a moving mouse and the effect of the surface of optical fibre. In the present study, we report on the characteristics of optical fibres to detect gene expression rhythm in freely moving mice. Using this portable optical device directly connected with a target area, we were able to measure the circadian rhythm of clock gene expression over a prolonged period in freely moving mice in a small space.
  • Teiji Nishio, Mitsuhiro Nakamura, Hiroyuki Okamoto, Satoshi Kito, Toshiyuki Minemura, Shuichi Ozawa, Yu Kumazaki, Masayori Ishikawa, Naoki Tohyama, Masahiko Kurooka, Takeo Nakashima, Hidetoshi Shimizu, Ryusuke Suzuki, Satoshi Ishikura, Yasumasa Nishimura
    Journal of radiation research 61 6 999 - 1008 2020年11月16日 
    The Japan Clinical Oncology Group-Radiation Therapy Study Group (JCOG-RTSG) has initiated several multicenter clinical trials for high-precision radiotherapy, which are presently ongoing. When conducting multi-center clinical trials, a large difference in physical quantities, such as the absolute doses to the target and the organ at risk, as well as the irradiation localization accuracy, affects the treatment outcome. Therefore, the differences in the various physical quantities used in different institutions must be within an acceptable range for conducting multicenter clinical trials, and this must be verified with medical physics consideration. In 2011, Japan's first Medical Physics Working Group (MPWG) in the JCOG-RTSG was established to perform this medical-physics-related verification for multicenter clinical trials. We have developed an auditing method to verify the accuracy of the absolute dose and the irradiation localization. Subsequently, we credentialed the participating institutions in the JCOG multicenter clinical trials that were using stereotactic body radiotherapy (SBRT) for lungs, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for several disease sites, and proton beam therapy (PT) for the liver. From the verification results, accuracies of the absolute dose and the irradiation localization among the participating institutions of the multicenter clinical trial were assured, and the JCOG clinical trials could be initiated.
  • Kazuko Hamada, Akari Oota, Ryoga Ito, Shigeru Kasahara, Kanako Nakajima, Yoshihiro Kikuchi, Kenneth Sutherland, Masayori Ishikawa, Hiroki Shirato, Michitaka Ozaki, Toshiyuki Hamada
    Biochemical and biophysical research communications 529 4 898 - 903 2020年09月03日 
    Clock genes express circadian rhythms in most organs. These rhythms are organized throughout the whole body, regulated by the suprachiasmatic nucleus (SCN) in the brain. Disturbance of these clock gene expression rhythms is a risk factor for diseases such as obesity and cancer. To understand the mechanism of regulating clock gene expression rhythms in vivo, multiple real time recording systems are required. In the present study, we developed a double recording system of Period1 expression rhythm in peripheral tissue (liver) and the brain. In peripheral tissue, quantification of gene expression in a steadily moving target was achieved by using a photomultiplier tube (PMT) attached to a tissue contact optical sensor (TCS). Using this technique, we were able to analyze circadian rhythms of clock gene expression over a prolonged period in the liver and olfactory bub (OB) of the brain. The present double recording system has no effect on behavioral activity or rhythm. Our novel system thus successfully quantifies clock gene expression in deep areas of the body in freely moving mice for a period sufficient to analyze circadian dynamics. In addition, our double recording system can be widely applied to many areas of biomedical research, as well as applications beyond medicine.
  • X線透視下手技における水晶体のリアルタイム被ばく計測の試み ファントム実験での検証
    作原 祐介, 高田 剛志, 古徳 純一, 石川 正純, 近藤 浩史
    日本インターベンショナルラジオロジー学会雑誌 35 Suppl. 169 - 169 (一社)日本インターベンショナルラジオロジー学会 2020年08月
  • Tamon Kusumoto, Yusuke Matsuya, Kentaro Baba, Ryo Ogawara, Mark S. Akselrod, Jonathan Harrison, Vasiliy Fomenko, Takeshi Kai, Masayori Ishikawa, Sumitaka Hasegawa, Satoshi Kodaira
    Radiation Measurements 132 2020年03月 [査読有り][通常論文]
     
    © 2020 Elsevier Ltd We report the dose measurement technique for emitted particles from Cu-64 source using a combination of Fluorescent Nuclear Track Detector (FNTD), which is Al2O3 single crystal doped with C and Mg, and Monte Carlo simulations in the PHITS code and Geant4 toolkit. The relatively high fluorescence intensity induced by Auger electrons is observed at the FNTD surface. Then, the fluorescence intensity monotonically reduces as the depth from the surface increases. The results obtained using the PHITS Monte Carlo simulation code is very similar to that of Geant4. Also, the simulations are in good agreement with experimental results. These findings prove that the signal induced by Auger electrons is successfully measured using FNTD. Additionally, the high signal at the FNTD surface implies that Auger electrons can work effectively to kill cancer cells proximal to a Cu-64 source while minimizing damage effects on normal cells distal to the source. At 15 μm depth in the crystal, which is the mean tissue cell radius, the relative dose of beta particles is about 24% of that at the FNTD surface. Therefore, the contribution of free radicals created by beta particles should be accounted for to clarify the impact of Cu-64 on tissues.
  • Yuma Kuga, Ryo Ogawara, Masayori Ishikawa
    Journal of radiation research 61 1 34 - 43 2020年01月23日 [査読有り][通常論文]
     
    In our laboratory we have confirmed that the capacitance of barium titanate-based capacitors changes due to radiation. Since a commercially available capacitor is very small and inexpensive, it may be used as a multidimensional dose meter in which a large number of capacitor elements are arranged, or may be embedded in the body and used as an in-vivo dose meter. In this study we examined the usefulness of a dosimeter using the capacitance change of a barium titanate capacitor. As a basic property, it was confirmed that the dose linearity was good. With regard to dose rate characteristics and response to fractionated irradiation, capacitance change due to aging affects measurement accuracy, but online measurement of capacitance change immediately before irradiation can be performed to correct aging effects during irradiation. By doing this, we confirmed that the dose rate characteristics and the response to fractionated radiation are improved.
  • Satoshi Takagi, Tatsuya Yaegashi, Masayori Ishikawa
    European radiology 30 1 571 - 580 2020年01月 
    OBJECTIVE: To clarify the relationship between entrance surface dose (ESD) and physical image quality of original and bone-suppressed chest radiographs acquired using high and low tube voltages. METHODS: An anthropomorphic chest phantom and a 12-mm diameter spherical simulated nodule with a CT value of approximately + 100 HU were used. The lung field in the chest radiograph was divided into seven areas, and the nodule was set in a total of 66 positions. A total of 264 chest radiographs were acquired using four ESD conditions: approximately 0.3 mGy at 140 and 70 kVp and approximately 0.2 and 0.1 mGy at 70 kVp. The radiographs were processed to produce bone-suppressed images. Differences in contrast and contrast-to-noise ratio (CNR) values of the nodule between each condition and between the original and bone-suppressed images were analyzed by a two-sided Wilcoxon signed-rank test. RESULTS: In the areas not overlapping with the ribs, both contrast and CNR values were significantly increased with the bone-suppression technique (p < 0.01). In the bone-suppressed images, these values of the three conditions at 70 kVp were equal to or significantly higher than those of the condition at 140 kVp. There was no apparent decrease in these values between the ESD of approximately 0.3 and 0.1 mGy at 70 kVp. CONCLUSION: By using the shortest exposure time and the lowest tube voltage possible not to increase in blurring artifact and image noise, it is possible to improve the image quality of bone-suppressed images and reduce the patient dose. KEY POINTS: • The effectiveness of bone-suppression techniques differs in areas of lung field. • Image quality of bone-suppressed chest radiographs is improved by lower tube voltage. • Applying lower tube voltage to bone-suppressed chest radiographs leads to dose reduction.
  • Katsuhiko Hirota, Takuro Tanaka, Naoki Iwata, Masayori Ishikawa
    Nihon Hoshasen Gijutsu Gakkai zasshi 76 8 817 - 827 2020年 
    In recent years, the exposure dose of the operator's eye lens during interventional radiology operations has become a problem. We therefore evaluated the feasibility of real-time lens dose measurement using scintillator with optical fiber (SOF) dosimeter. Given that the SOF dosimeter is calibrated for direct X-rays, we performed a calibration for scattered X-rays to investigate energy dependence and the accuracy of lens dose measurements. The detection limit was calculated using the Kaiser method. The SOF dosimeter and the radiophotoluminescence glass (RPLG) dosimeter were attached to the protective glasses worn by the operator, and the lens exposure dose of the operator during cardiac catheterization was measured. In the phantom experiment, the SOF dosimeter had an error rate of 5.45% based on the measured value of the ionization chamber dosimeter. The sensitivity characteristics of the SOF dosimeter were slightly reduced on the higher side of the effective energy. The difference in sensitivity was related to variations in the additional filter and energy dependency. The sensitivity difference was 18.5% at maximum. Furthermore, when the additional dose was displayed, the influence of noise on long-term measurement was considerable. Using the Kaiser method to obtain the detection limit, the accuracy of the integrated dose had SOF dosimeter error rates of 4.3% to 15.5% with respect to the integrated value of the RPLG dosimeter when calibrated by the ionization chamber dosimeter. The use of the SOF dosimeter allowed for the real-time visualization of the exposure status of the eye lens and measurements with a relatively high accuracy.
  • リアルタイム被ばく計測の試み ファントム実験での検証
    作原 祐介, 中村 友亮, 清水 匡, 石川 正純, 高田 剛志, 古徳 純一, 近藤 浩史
    日本インターベンショナルラジオロジー学会雑誌 34 2 163 - 163 (一社)日本インターベンショナルラジオロジー学会 2019年12月
  • Yuichi Akino, Naoki Tohyama, Kazuhiko Akita, Masayori Ishikawa, Ryu Kawamorita, Masahiko Kurooka, Iori Sumida, Yuji Nakaguchi, Kazunori Miyaura, Mitsuhiro Nakamura
    Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB) 64 182 - 187 2019年08月 
    Over the last several decades, there have been great advances in radiotherapy with the development of new technologies and modalities, and radiotherapy trends have changed rapidly. To comprehend the current state of radiotherapy in Japan, the QA/QC 2016-2017 Committee of the Japan Society of Medical Physics set up an intensity-modulated radiotherapy/image-guided radiotherapy (IMRT/IGRT) working group and performed a Web-based survey to show the current status of radiotherapy in Japan. The Web-based questionnaire, developed using Google Forms, contained 42 items: 7 on stereotactic radiotherapy implementation, 4 on IMRT, 24 on IGRT, and 7 on respiratory motion management. The survey was conducted from 17 January to 9 March of 2018; in total, 335 institutions provided data. The results show that volumetric modulated arc therapy was used at a level comparable to that of static gantry IMRT. For IGRT, machine-integrated computed tomography (CT), including kilovoltage or megavoltage cone-beam CT and megavoltage CT, was used at many institutions in conjunction with target-based image registration. For respiratory motion management, breath holding was the most commonly used technique. Our hope is that multi-institutional surveys such as this one will be conducted periodically to elucidate the current status of radiotherapy and emerging developments in this field. If our questionnaire was distributed worldwide, in the same format, then global trends in radiotherapy could be better understood.
  • Yusuke Matsuya, Yukihiko Satou, Nobuyuki Hamada, Hiroyuki Date, Masayori Ishikawa, Tatsuhiko Sato
    Scientific reports 9 1 10365 - 10365 2019年07月17日 [査読有り][通常論文]
     
    Insoluble radioactive microparticles emitted by the incident at the Fukushima nuclear power plant have drawn keen interests from the viewpoint of radiation protection. Cs-bearing particles have been assumed to adhere in the long term to trachea after aspirated into respiratory system, leading to heterogeneous dose distribution within healthy tissue around the particles. However, the biological effects posed by an insoluble radioactive particle remain unclear. Here, we show cumulative DNA damage in normal human lung cells proximal and distal to the particle (β-ray and γ-ray-dominant areas, respectively) under localized chronic exposure in comparison with uniform exposure. We put a Cs-bearing particle into a microcapillary tip and placed it onto a glass-base dish containing fibroblast or epithelial cells cultured in vitro. A Monte Carlo simulation with PHITS code provides the radial distribution of absorbed dose-rate around the particle, and subsequently we observed a significant change in nuclear γ-H2AX foci after 24 h or 48 h exposure to the particle. The nuclear foci in the cells distal to the particle increased even under low-dose-rate exposure compared with uniform exposure to 137Cs γ-rays, which was suppressed by a treatment with a scavenger of reactive oxygen species. In contrast, such focus formation was less manifested in the exposed cells proximal to the particle compared with uniform exposure. These data suggest that the localized exposure to a Cs-bearing particle leads to not only disadvantage to distal cells but also advantage to proximal cells. This study is the first to provide quantitative evaluation for the spatial distribution of DNA double strand breaks after the heterogeneous chronic exposure to a Cs-bearing particle in comparison with uniform Cs exposure.
  • Satoshi Takagi, Tatsuya Yaegashi, Masayori Ishikawa
    Academic radiology 26 7 e174-e179  2019年07月 [査読有り][通常論文]
     
    RATIONALE AND OBJECTIVES: Image quality of chest radiographs is affected by tube voltage. This study aimed to clarify the relationship between tube voltage and physical image quality of pulmonary nodules on bone-suppressed chest radiographs. MATERIALS AND METHODS: An anthropomorphic chest phantom and a spherical simulated nodule, with a 12-mm diameter and approximately +100 Hounsfield units were used. The lung field of the phantom was divided into three areas, based on the overlap with the ribs in the chest radiograph. Ten positions of the simulated nodule were defined in each area. One hundred and twenty chest radiographs were acquired using four tube voltages (70 kVp, 90 kVp, 110 kVp, and 130 kVp) for a total of 30 nodule positions and were processed to create bone-suppressed images. Differences in contrast and contrast-to-noise ratio (CNR) were analyzed for all pairs of the four tube voltages using a two-sided Wilcoxon signed-rank test. RESULTS: In the area not overlapping with ribs, a statistically significant difference was observed only in contrast between tube voltage of 70 kVp and 90 kVp (p = 0.01). In the area overlapping with one or two ribs, the contrast and CNR tended to be higher at a lower tube voltage. In particular, the p values between the contrast at 70 kVp and that at the other three tube voltage settings were less than 0.01. CONCLUSION: For a relatively dense nodule, the contrast and CNR in the bone-suppressed chest radiograph were significantly improved with lower tube voltage in the lung field overlapping with the ribs.
  • Masayori Ishikawa, Kentaro Baba, Ryo Ogawara, Naoto Shimizu, Yoshinori Sakurai
    2019 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (NSS/MIC) 2019年 
    Boron Neutron Capture Therapy (BNCT) is a radiation cancer treatment that uses energy generated by the nuclear reaction between boron and neutrons to kill the tumor cells by accumulating boron compounds on the tumor cells and irradiating them with neutrons. In recent years, BNCT treatment using an accelerator has come to a feasible stage. Since BNCT treatment using an accelerator contains a large amount of epithermal neutron components, it is difficult to evaluate the amount of neutron irradiation using a gold activation method as in the past. Further, in the BNCT treatment, since the neutron dose is controlled by the durable dose of the skin irradiated with the neutron beam, it is desirable to be able to measure the dose per neutron energy component on the skin surface.We have developed a SOF detector (Scintillator with Optical Fiber Detector) for measuring thermal neutron flux in real time, and reported on the usefulness of real time measurement in clinic. The SOF detector uses nuclear reaction energy by neutron sensitizers, but the energy response differs depending on the nuclide of the neutron sensitizer. In this study, we developed a new neutron energy spectrometer that can simultaneously evaluate thermal neutrons, epithermal neutrons, and gamma dose by upgrading conventional SOF detector which is combining many scintillators containing different neutron sensitizers.
  • 3D Transformation Matrix Calculation and Pixel Intensity Normalization for the Dual Focus Tracking System
    Kenneth Sutherland, Toshiyuki Hamada, Masayori Ishikawa, Naoki Miyamoto, Masahiro Mizuta, Hiroyuki Date, Hiroki Shirato
    Journal of Medical and Biological Engineering 2019年 [査読有り][通常論文]
  • IVR術施行中のリアルタイム被ばく線量測定の試み
    石川 正純
    日本インターベンショナルラジオロジー学会誌 32 4 19 - 25 2018年 [査読有り][通常論文]
  • Hideki Kojima, Makoto Takigami, Tomohiro Asano, Yasuhiro Hatanaka, Kazuhiro Aizawa, Masayori Ishikawa
    Nihon Hoshasen Gijutsu Gakkai zasshi 73 5 382 - 388 2017年 [査読有り][通常論文]
     
    In dynamic multi-leaf collimator (MLC) intensity-modulated radiotherapy (IMRT), the accuracy of delivered dose is influenced by the positional accuracy of the moving MLC. In order to assess the accuracy of the delivered dose during dynamic MLC IMRT, the delivered dose error in dynamic MLC IMRT using the MLC speed control with dose rate change was investigated. Sweeping gap sequence irradiation was performed with constant MLC leaf speed at 0.6 to 5 cm/s or changed MLC speed (4 steps). The positional accuracy of the moving MLC was evaluated from the trajectory log file. Absorbed dose measurements with sweeping field (Field size: 10 cm×10 cm, MLC leaf speed: 0.6 to 2.7 cm/s, MLC leaf gap width: 0.2 to 2.0 cm) were performed. The delivered dose error at each gap width was evaluated according to MLC leaf speed change. MLC positional errors and changes in delivered dose according to MLC leaf speed were within 0.07 mm and 0.6%, respectively, for all measurements. Beam hold-off did not occur under any conditions. We confirmed that TrueBeam can regulate MLC leaf speed below the maximum limit (2.5 cm/s) by changing the dose rate in real-time during irradiation in dynamic MLC IMRT. MLC gap error during irradiation was estimated within 0.2 mm at the maximum dose rate from the results of absolute dose measurements using dynamic MLC irradiation. In conclusion, TrueBeam can use the maximum dose rate for the treatment planning of dynamic MLC IMRT, which has an advantage of shorter treatment time.
  • 石川 正純
    臨床放射線 62 2 257 - 263 2017年 [査読有り][通常論文]
  • 自由行動マウスの複数組織における時計遺伝子発現のin vivo追跡定量化 (Best articles of the year)
    浜田俊幸, ケネスリーサザーランド, 石川正純, 宮本直樹, 本間さと, 白土博樹, 本間研一
    The Hokkaido Journal of Medical Science 91 2 2016年11月 [査読有り][通常論文]
  • Masayori Ishikawa, Tetsuya Yamamoto, Akira Matsumura, Junichi Hiratsuka, Shin-Ichi Miyatake, Itsuro Kato, Yoshinori Sakurai, Hiroaki Kumada, Shubhechha J. Shrestha, Koji Ono
    RADIATION ONCOLOGY 11 105 2016年08月 [査読有り][通常論文]
     
    Background: Real-time measurement of thermal neutrons in the tumor region is essential for proper evaluation of the absorbed dose in boron neutron capture therapy (BNCT) treatment. The gold wire activation method has been routinely used to measure the neutron flux distribution in BNCT irradiation, but a real-time measurement using gold wire is not possible. To overcome this issue, the scintillator with optical fiber (SOF) detector has been developed. The purpose of this study is to demonstrate the feasibility of the SOF detector as a real-time thermal neutron monitor in clinical BNCT treatment and also to report issues in the use of SOF detectors in clinical practice and their solutions. Material and methods: Clinical measurements using the SOF detector were carried out in 16 BNCT clinical trial patients from December 2002 until end of 2006 at the Japanese Atomic Energy Agency (JAEA) and Kyoto University Research Reactor Institute (KURRI). Results: The SOF detector worked effectively as a real-time thermal neutron monitor. The neutron fluence obtained by the gold wire activation method was found to differ from that obtained by the SOF detector. The neutron fluence obtained by the SOF detector was in better agreement with the expected fluence than with gold wire activation. The estimation error for the SOF detector was small in comparison to the gold wire measurement. In addition, real-time monitoring suggested that the neutron flux distribution and intensity at the region of interest (ROI) may vary due to the reactor condition, patient motion and dislocation of the SOF detector. Conclusion: Clinical measurements using the SOF detector to measure thermal neutron flux during BNCT confirmed that SOF detectors are effective as a real-time thermal neutron monitor. To minimize the estimation error due to the displacement of the SOF probe during treatment, a loop-type SOF probe was developed.
  • R. Ogawara, M. Ishikawa
    Review of Scientific Instruments 87 7 Epub. 075114  2016年07月01日 [査読有り][通常論文]
     
    The anode pulse of a photomultiplier tube (PMT) coupled with a scintillator is used for pulse shape discrimination (PSD) analysis. We have developed a novel emulation technique for the PMT anode pulse based on optical photon transport and a PMT response function. The photon transport was calculated using Geant4 Monte Carlo code and the response function with a BC408 organic scintillator. The obtained percentage RMS value of the difference between the measured and simulated pulse with suitable scintillation properties using GSO:Ce (0.4, 1.0, 1.5 mol%), LaBr3:Ce and BGO scintillators were 2.41%, 2.58%, 2.16%, 2.01%, and 3.32%, respectively. The proposed technique demonstrates high reproducibility of the measured pulse and can be applied to simulation studies of various radiation measurements.
  • Toshiyuki Hamada, Kenneth Sutherland, Masayori Ishikawa, Naoki Miyamoto, Sato Honma, Hiroki Shirato, Ken-Ichi Honma
    Nature communications 7 11705 - 11705 2016年06月10日 [査読有り][通常論文]
     
    Clock genes are expressed throughout the body, although how they oscillate in unrestrained animals is not known. Here, we show an in vivo imaging technique that enables long-term simultaneous imaging of multiple tissues. We use dual-focal 3D tracking and signal-intensity calibration to follow gene expression in a target area. We measure circadian rhythms of clock genes in the olfactory bulb, right and left ears and cortices, and the skin. In addition, the kinetic relationship between gene expression and physiological responses to experimental cues is monitored. Under stable conditions gene expression is in phase in all tissues. In response to a long-duration light pulse, the olfactory bulb shifts faster than other tissues. In Cry1(-/-) Cry2(-/-) arrhythmic mice circadian oscillation is absent in all tissues. Thus, our system successfully tracks circadian rhythms in clock genes in multiple tissues in unrestrained mice.
  • 原田慶一, 加藤徳雄, 井上哲也, 鬼丸力也, 清水伸一, 白土博樹, 鈴木隆介, 宮本直樹, 石川正純
    Japanese Journal of Radiology 34 Supplement 10 - 10 (公社)日本医学放射線学会 2016年02月25日 [査読無し][通常論文]
  • 宮本直樹, 高尾聖心, 原田慶一, 石川正純, 鈴木隆介, 松浦妙子, 牧永彩乃, 井上哲也, 加藤徳雄, 清水伸一, 鬼丸力也, 白土博樹
    日本放射線腫瘍学会高精度放射線外部照射部会学術大会プログラム・抄録集 29th 46  2016年 [査読無し][通常論文]
  • Naoyuki Ukon, Naoki Kubo, Masayori Ishikawa, Songji Zhao, Nagara Tamaki, Yuji Kuge
    Results in Physics 6 659 - 663 2016年 [査読有り][通常論文]
     
    Focusing on whole-body uniformity in small-animal single-photon emission computed tomography (SPECT), we examined the optimal helical acquisition parameters using five-pinhole collimators for mouse imaging. SPECT images of an 80-mm-long cylindrical phantom with 99mTc solution were acquired using an Inveon multimodality imaging platform. The bed travels used in this study were 0, 30, 60, 90 and 120 mm, and the numbers of revolutions traversed during the SPECT scan were 1.0, 2.0, 3.0, 4.0, 5.0 and 7.0, respectively. Artifacts that degrade uniformity in reconstructed images were conspicuous when the bed travel was smaller than the object length. Regarding the distal-to-center ratio (DCR) of SPECT values in the object's axial direction, the DCR nearest to the ideal ratio of 1.00 was 1.02 in the optimal uniformity with 4.0 revolutions and a bed travel of 120 mm. Moreover, the helical acquisition using these parameters suppressed the formation of artifacts. We proposed the optimal parameters in whole-body helical SPECT; the bed travel was sufficiently larger than the object length; the 4.0 or more revolutions were required for a pitch of approximately 30 mm/revolution. The optimal acquisition parameters in SPECT to preserve uniformity would contribute to the accurate quantification of whole-body biodistribution. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
  • R. Ogawara, M. Ishikawa
    REVIEW OF SCIENTIFIC INSTRUMENTS 86 8 Epub. 085108  2015年08月 [査読有り][通常論文]
     
    A novel analysis method named peak-to-charge ratio (V-p/Q(total)) discrimination, aiming at background rejection especially for alpha decay self-activity in LaBr3:Ce scintillators has been developed. This method is based on a waveform analysis using the peak-to-charge ratio in the output waveform of a photomultiplier tube. The discrimination of alpha-induced events was achieved by using a threshold function based on the error propagation of the V-p/Q(total) value. The accidental rejection ratio of gamma-induced events was evaluated to be 0.17%. Furthermore, a total absorption peak spectrum processed with the V-p/Q(total) discrimination method for Ga-68 1.883 MeV gamma rays, where the energy was overlapped with background alpha events, reproduced exactly the same result as that of the background subtraction method. The difference in measured peak counts of both methods was 0.716%, and the statistical error in the V-p/Q(total) discrimination method and background subtraction was 4.81% and 8.70%, respectively. Thus a higher-accuracy measurement could be achieved using the V-p/Q(total) discrimination method. The present study demonstrates that the V-p/Q(total) discrimination method is a promising method for background rejection of the spontaneous alpha decay in LaBr3: Ce scintillators. (C) 2015 AIP Publishing LLC.
  • Jun Kunimatsu, Naoki Miyamoto, Masayori Ishikawa, Hiroki Shirato, Masaki Tanaka
    Frontiers in systems neuroscience 9 67 - 67 2015年04月24日 [査読有り][通常論文]
     
    Behavioral analysis of subjects with discrete brain lesions provides important information about the mechanisms of various brain functions. However, it is generally difficult to experimentally produce discrete lesions in deep brain structures. Here we show that a radiosurgical technique, which is used as an alternative treatment for brain tumors and vascular malformations, is applicable to create non-invasive lesions in experimental animals for the research in systems neuroscience. We delivered highly focused radiation (130–150 Gy at ISO center) to the frontal eye field (FEF) of macaque monkeys using a clinical linear accelerator (LINAC). The effects of irradiation were assessed by analyzing oculomotor performance along with magnetic resonance (MR) images before and up to 8 months following irradiation. In parallel with tissue edema indicated by MR images, deficits in saccadic and smooth pursuit eye movements were observed during several days following irradiation. Although initial signs of oculomotor deficits disappeared within a month, damage to the tissue and impaired eye movements gradually developed during the course of the subsequent 6 months. Postmortem histological examinations showed necrosis and hemorrhages within a large area of the white matter and, to a lesser extent, in the adjacent gray matter, which was centered at the irradiated target. These results indicated that the LINAC system was useful for making brain lesions in experimental animals, while the suitable radiation parameters to generate more focused lesions need to be further explored. We propose the use of a radiosurgical technique for establishing animal models of brain lesions, and discuss the possible uses of this technique for functional neurosurgical treatments in humans.
  • Masayori Ishikawa, Naomi Nagase, Taeko Matsuura, Junichi Hiratsuka, Ryusuke Suzuki, Naoki Miyamoto, Kenneth Lee Sutherland, Katsuhisa Fujita, Hiroki Shirato
    JOURNAL OF RADIATION RESEARCH 56 2 372 - 381 2015年03月 [査読有り][通常論文]
     
    The scintillator with optical fiber (SOF) dosimeter consists of a miniature scintillator mounted on the tip of an optical fiber. The scintillator of the current SOF dosimeter is a 1-mm diameter hemisphere. For a scintillation dosimeter coupled with an optical fiber, measurement accuracy is influenced by signals due to Cerenkov radiation in the optical fiber. We have implemented a spectral filtering technique for compensating for the Cerenkov radiation effect specifically for our plastic scintillator-based dosimeter, using a wavelength-separated counting method. A dichroic mirror was used for separating input light signals. Individual signal counting was performed for high-and low-wavelength light signals. To confirm the accuracy, measurements with various amounts of Cerenkov radiation were performed by changing the incident direction while keeping the Ir-192 source-to-dosimeter distance constant, resulting in a fluctuation of <5%. Optical fiber bending was also addressed; no bending effect was observed for our wavelength-separated SOF dosimeter.
  • Masayori Ishikawa, Kenichi Tanaka, Satrou Endo, Masaharu Hoshi
    JOURNAL OF RADIATION RESEARCH 56 2 391 - 396 2015年03月 [査読有り][通常論文]
     
    Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 10(5) n/cm(2)/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources.
  • Seiichiro Ishihara, Motoaki Yasuda, Akihiro Ishizu, Masayori Ishikawa, Hiroki Shirato, Hisashi Haga
    ONCOTARGET 6 7 4602 - 4614 2015年03月 [査読有り][通常論文]
     
    Radiotherapy is effective for treating various types of tumors. However, some cancer cells survive after irradiation and repopulate tumors with highly malignant phenotypes that correlate with poor prognosis. It is not known how cancer cells survive and generate malignant tumors after irradiation. Here, we show that activating transcription factor 5 (ATF5) promotes radioresistance and malignancy in cancer cells after irradiation. In the G1-S phase of the cell cycle, cancer cells express high levels of ATF5, which promotes cell cycle progression and thereby increases radioresistance. Furthermore, ATF5 increases malignant phenotypes, such as cell growth and invasiveness, in cancer cells in vitro and in vivo. We have identified a new mechanism for the regeneration of highly malignant tumors after irradiation and shown that ATF5 plays a key role in the process.
  • Masayori Ishikawa, Naomi Nagase, Taeko Matsuura, Junichi Hiratsuka, Ryusuke Suzuki, Naoki Miyamoto, Kenneth Lee Sutherland, Katsuhisa Fujita, Hiroki Shirato
    JOURNAL OF RADIATION RESEARCH 56 2 372 - 381 2015年03月 [査読有り][通常論文]
     
    The scintillator with optical fiber (SOF) dosimeter consists of a miniature scintillator mounted on the tip of an optical fiber. The scintillator of the current SOF dosimeter is a 1-mm diameter hemisphere. For a scintillation dosimeter coupled with an optical fiber, measurement accuracy is influenced by signals due to Cerenkov radiation in the optical fiber. We have implemented a spectral filtering technique for compensating for the Cerenkov radiation effect specifically for our plastic scintillator-based dosimeter, using a wavelength-separated counting method. A dichroic mirror was used for separating input light signals. Individual signal counting was performed for high-and low-wavelength light signals. To confirm the accuracy, measurements with various amounts of Cerenkov radiation were performed by changing the incident direction while keeping the Ir-192 source-to-dosimeter distance constant, resulting in a fluctuation of <5%. Optical fiber bending was also addressed; no bending effect was observed for our wavelength-separated SOF dosimeter.
  • Naoki Miyamoto, Masayori Ishikawa, Kenneth Sutherland, Ryusuke Suzuki, Taeko Matsuura, Chie Toramatsu, Seishin Takao, Hideaki Nihongi, Shinichi Shimizu, Kikuo Umegaki, Hiroki Shirato
    JOURNAL OF RADIATION RESEARCH 56 1 186 - 196 2015年01月 [査読有り][通常論文]
     
    In the real-time tumor-tracking radiotherapy system, a surrogate fiducial marker inserted in or near the tumor is detected by fluoroscopy to realize respiratory-gated radiotherapy. The imaging dose caused by fluoroscopy should be minimized. In this work, an image processing technique is proposed for tracing a moving marker in low-dose imaging. The proposed tracking technique is a combination of a motion-compensated recursive filter and template pattern matching. The proposed image filter can reduce motion artifacts resulting from the recursive process based on the determination of the region of interest for the next frame according to the current marker position in the fluoroscopic images. The effectiveness of the proposed technique and the expected clinical benefit were examined by phantom experimental studies with actual tumor trajectories generated from clinical patient data. It was demonstrated that the marker motion could be traced in low-dose imaging by applying the proposed algorithm with acceptable registration error and high pattern recognition score in all trajectories, although some trajectories were not able to be tracked with the conventional spatial filters or without image filters. The positional accuracy is expected to be kept within +/- 2 mm. The total computation time required to determine the marker position is a few milliseconds. The proposed image processing technique is applicable for imaging dose reduction.
  • 【放射線治療活用BOOK 2014】 (DIVISION-3)これからの放射線治療の展望 最新の動体追跡放射線治療装置
    宮本 直樹, 石川 正純, 松浦 妙子, 井上 哲也, 加藤 徳雄, 清水 伸一, 鬼丸 力也, 梅垣 菊男, 白土 博樹
    Rad Fan 12 15 75 - 77 (株)メディカルアイ 2014年12月 [査読無し][通常論文]
     
    動体追跡法は、日本が世界に先駆けて実現してきた治療法であり、多くの実績を有する。本稿では、最新の迎撃照射型動体追跡装置として、島津製作所からリリースされたX線治療用動体追跡装置「SyncTraX」、日立製作所からリリースされた動体追跡陽子線スポットスキャニングシステム「PROBEAT-RT」について、その特徴と利点を紹介する。(著者抄録)
  • Teiji Nishio, Hiroki Shirato, Masayori Ishikawa, Yuki Miyabe, Satoshi Kito, Yuichirou Narita, Rikiya Onimaru, Satoshi Ishikura, Yoshinori Ito, Masahiro Hiraoka
    JOURNAL OF RADIATION RESEARCH 55 3 600 - 607 2014年05月 [査読有り][通常論文]
     
    A domestic multicenter phase I study of stereotactic body radiotherapy (SBRT) for T2N0M0 non-small cell lung cancer in inoperable patients or elderly patients who refused surgery was initiated as the Japan Clinical Oncology Group trial (JCOG0702) in Japan. Prior to the clinical study, the accuracy of dose calculation in radiation treatment-planning systems was surveyed in participating institutions, and differences in the irradiating dose between the institutions were investigated. We developed a water tank-type lung phantom appropriate for verification of the exposure dose in lung SBRT. Using this water tank-type lung phantom, the dose calculated in the radiation treatment-planning system and the measured dose using a free air ionization chamber and dosimetric film were compared in a visiting survey of the seven institutions participating in the clinical study. In all participating institutions, differences between the calculated and the measured dose in the irradiation plan were as follows: the accuracy of the absolute dose in the center of the simulated tumor measured using a free air ionization chamber was within 2%, the mean gamma value was <= 0.47 on gamma analysis following the local dose criteria, and the pass rate was >87% for 3%/3 mm from measurement of dose distribution with dosimetric film. These findings confirmed the accuracy of delivery doses in the institutions participating in the clinical study, so that a study with integration of the institutions could be initiated.
  • Hiro-taka Masuda, Seiichiro Ishihara, Ichiro Harada, Takeomi Mizutani, Masayori Ishikawa, Kazushige Kawabata, Hisashi Haga
    BIOTECHNIQUES 56 4 172 - 179 2014年04月 [査読有り][通常論文]
     
    We demonstrate that a (3-aminopropyl)triethoxysilane-treated glass surface is superior to an untreated glass surface for coating with extracellular matrix (ECM) proteins when used as a cell culture substrate to observe cell physiology and behavior. We found that MDCK cells cultured on untreated glass coated with ECM removed the coated ECM protein and secreted different ECM proteins. In contrast, the cells did not remove the coated ECM protein when seeded on (3-aminopropyl)triethoxysilane-treated (i.e., silanized) glass coated with ECM. Furthermore, the morphology and motility of cells grown on silanized glass differed from those grown on non-treated glass, even when both types of glass were initially coated with laminin. We also found that cells on silanized glass coated with laminin had higher motility than those on silanized glass coated with fibronectin. Based on our results, we suggest that silanized glass is a more suitable cell culture substrate than conventional non-treated glass when coated by ECM for observations of ECM effects on cell physiology.
  • 西川由記子, 原田慶一, 西岡健太郎, 安田耕一, 井上哲也, 土屋和彦, 小野寺俊輔, 木下留美子, 加藤徳雄, 清水伸一, 鬼丸力也, 白土博樹, 鈴木隆介, 石川正純
    Jpn J Radiol 32 Supplement 5 - 5 (公社)日本医学放射線学会 2014年02月25日 [査読無し][通常論文]
  • Nishio T, Shirato H, Ishikawa M, Miyabe Y, Kito S, Narita Y, Onimaru R, Ishikura S, Ito Y, Hiraoka M
    J Radiat Res 55 3 600 - 7 2014年 [査読有り][通常論文]
  • Clinical application of scintillator with optical fiber detector as a real-time thermal neutron monitor during boron neutron capture therapy
    M.Ishikawa, K.Ono, A.Matsumura, T.Yamamoto, J.Hiratsuka, S.Miyatake, I.Kato, Y.Sakurai, H.Kumada
    Book of Abstracts for the 7th Korea-Japan Joint Meeting on Medical Physics, The Korean Society of Medical Physics 129  2014年 [査読無し][通常論文]
  • Satoshi Tanabe, Miyako Myojin, Shinichi Shimizu, Masaharu Fujino, Hiroaki Takahashi, Hiroki Shirato, Yoichi M. Ito, Masayori Ishikawa, Masao Hosokawa
    Journal of Radiation Research 54 6 1085 - 1094 2013年11月 [査読有り][通常論文]
     
    Purpose: We evaluated the relationship between dosimetric parameters (DPs) and the incidence of radiation pneumonitis (RP) and investigated the feasibility of a proposed treatment planning technique with the potential of reducing RP in esophageal cancer patients treated with definitive chemoradiotherapy using extended fields. Patients and Methods: A total of 149 patients with locally advanced esophageal cancer were prospectively enrolled for extended-field radiotherapy (EFRT) to three-field regional lymphatics between September 2004 and June 2009. We retrospectively reviewed 86 consecutive patients who were treated with a total dose of 50.4 Gy ( plus an optional 9 Gy boost) and were available for dose-volume analysis. Lung DPs of patients in the Grade 0 1 RP (RPG≤1) group and the Grade 2 5 RP (RPG≥2) group were compared. We compared the proposed plan with the conventional plan to 50.4 Gy on DPs for each case. Results: Of these 86 patients, 10 (12%) developed RPG≥2 (Grade 2, n = 2 patients Grade 3, n = 3 Grade 4, n = 3 Grade 5, n = 2). The patients in the RPG≤1 group showed significantly lower (P < 0.05) V5 and V10 values for the whole lung compared with those in the RPG≥2 group. There were two advantages gained from the proposed plan for V5 (< 55%) and V10 (< 37%) values and the conformity of the PTV. Conclusion: The increase in the volume of the lung exposed to low doses of EFRT was found to be associated with the incidence of RP. Our proposed plan is likely to reduce the incidence of RP. © The Author 2013. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Therapeutic Radiology and Oncology.
  • Li X, Ishihara S, Yasuda M, Nishioka T, Mizutani T, Ishikawa M, Kawabata K, Shirato H, Haga H
    PloS one 8 8 e70905  2013年08月 [査読有り][通常論文]
     
    Ionizing radiation (IR)-enhanced tumor invasiveness is emerging as a contributor to the limited benefit of radiotherapy; however, its mechanism is still unclear. We previously showed that subcloned lung adenocarcinoma A549 cells (P cells), which survived 10 Gy IR (IR cells), acquired high invasiveness in vitro. Here, we tried to identify the mechanism by which IR cells increase their invasiveness by examining altered gene expression and signaling pathways in IR cells compared with those in P cells. To simulate the microenvironment in vivo, cells were embedded in a three-dimensional (3D) collagen type I gel, in which the IR cells were elongated, while the P cells were spherical. The integrin expression pattern was surveyed, and expression levels of the integrin alpha 2 and beta 1 subunits were significantly elevated in IR cells. Knockdown of alpha 2 expression or functional blockade of integrin alpha 2 beta 1 resulted in a round morphology of IR cells, and abrogated their invasion in the collagen matrix, suggesting the molecule's essential role in cell spread and invasion in 3D collagen. Epidermal growth factor receptor (EGFR) also presented enhanced expression and activation in IR cells. Treatment with EGFR tyrosine kinase inhibitor, PD168393, decreased the ratio of elongated cells and cell invasiveness. Signaling molecules, including extracellular signal-regulated kinase-1/2 (Erk1/2) and Akt, exhibited higher activation in IR cells. Inhibition of Akt activation by treating with phosphoinositide 3-kinase (PI3K) inhibitor LY294002 decreased IR cell invasion, whereas inhibition of Erk1/2 activation by mitogen-activated protein kinase kinase (MEK) inhibitor U0126 did not. Our results show that integrin alpha 2 beta 1 and EGFR cooperatively promote higher invasiveness of IR-survived lung cancer cells, mediated in part by the PI3K/Akt signaling pathway, and might serve as alternative targets in combination with radiotherapy.
  • Nam JM, Ahmed KM, Costes S, Zhang H, Onodera Y, Olshen AB, Hatanaka KC, Kinoshita R, Ishikawa M, Sabe H, Shirato H, Park CC
    Breast cancer research : BCR 15 4 R60  2013年07月25日 [査読有り][通常論文]
     
    Introduction: Ductal carcinoma in situ (DCIS) is characterized by non-invasive cancerous cell growth within the breast ducts. Although radiotherapy is commonly used in the treatment of DCIS, the effect and molecular mechanism of ionizing radiation (IR) on DCIS are not well understood, and invasive recurrence following radiotherapy remains a significant clinical problem. This study investigated the effects of IR on a clinically relevant model of Akt-driven DCIS and identified possible molecular mechanisms underlying invasive progression in surviving cells.Methods: We measured the level of phosphorylated-Akt (p-Akt) in a cohort of human DCIS specimens by immunohistochemistry (IHC) and correlated it with recurrence risk. To model human DCIS, we used Akt overexpressing human mammary epithelial cells (MCF10A-Akt) which, in three-dimensional laminin-rich extracellular matrix (lrECM) and in vivo, form organotypic DCIS-like lesions with lumina expanded by pleiomorphic cells contained within an intact basement membrane. In a population of cells that survived significant IR doses in three-dimensional lrECM, a malignant phenotype emerged creating a model for invasive recurrence.Results: P-Akt was up-regulated in clinical DCIS specimens and was associated with recurrent disease. MCF10A-Akt cells that formed DCIS-like structures in three-dimensional lrECM showed significant apoptosis after IR, preferentially in the luminal compartment. Strikingly, when cells that survived IR were repropagated in three-dimensional lrECM, a malignant phenotype emerged, characterized by invasive activity, up-regulation of fibronectin, α5β1-integrin, matrix metalloproteinase-9 (MMP-9) and loss of E-cadherin. In addition, IR induced nuclear translocation and binding of nuclear factor-kappa B (NF-κB) to the β1-integrin promoter region, associated with up-regulation of α5β1-integrins. Inhibition of NF-κB or β1-integrin signaling abrogated emergence of the invasive activity.Conclusions: P-Akt is up-regulated in some human DCIS lesions and is possibly associated with recurrence. MCF10A-Akt cells form organotypic DCIS-like lesions in three-dimensional lrECM and in vivo, and are a plausible model for some forms of human DCIS. A population of Akt-driven DCIS-like spheroids that survive IR progresses to an invasive phenotype in three-dimensional lrECM mediated by β1-integrin and NF-κB signaling. © 2013 Nam et al. licensee BioMed Central Ltd.
  • 白土博樹, 鬼丸力也, 清水伸一, 石川正純, 宮本直樹, SUTHERLAND Ken, 鈴木隆介, 寅松千枝
    映像情報Medical 45 7 619 - 623 2013年07月01日 [査読無し][通常論文]
  • Taeko Matsuura, Naoki Miyamoto, Shinichi Shimizu, Yusuke Fujii, Masumi Umezawa, Seishin Takao, Hideaki Nihongi, Chie Toramatsu, Kenneth Sutherland, Ryusuke Suzuki, Masayori Ishikawa, Rumiko Kinoshita, Kenichiro Maeda, Kikuo Umegaki, Hiroki Shirato
    MEDICAL PHYSICS 40 7 071729  2013年07月 [査読有り][通常論文]
     
    Purpose: In spot-scanning proton therapy, the interplay effect between tumor motion and beam delivery leads to deterioration of the dose distribution. To mitigate the impact of tumor motion, gating in combination with repainting is one of the most promising methods that have been proposed. This study focused on a synchrotron-based spot-scanning proton therapy system integrated with real-time tumor monitoring. The authors investigated the effectiveness of gating in terms of both the delivered dose distribution and irradiation time by conducting simulations with patients' motion data. The clinically acceptable range of adjustable irradiation control parameters was explored. Also, the relation between the dose error and the characteristics of tumor motion was investigated. Methods: A simulation study was performed using a water phantom. A gated proton beam was irradiated to a clinical target volume (CTV) of 5 x 5 x 5 cm(3), in synchronization with lung cancer patients' tumor trajectory data. With varying parameters of gate width, spot spacing, and delivered dose per spot at one time, both dose uniformity and irradiation time were calculated for 397 tumor trajectory data from 78 patients. In addition, the authors placed an energy absorber upstream of the phantom and varied the thickness to examine the effect of changing the size of the Bragg peak and the number of required energy layers. The parameters with which 95% of the tumor trajectory data fulfill our defined criteria were accepted. Next, correlation coefficients were calculated between the maximum dose error and the tumor motion characteristics that were extracted from the tumor trajectory data. Results: With the assumed CTV, the largest percentage of the data fulfilled the criteria when the gate width was +/- 2 mm. Larger spot spacing was preferred because it increased the number of paintings. With a prescribed dose of 2 Gy, it was difficult to fulfill the criteria for the target with a very small effective depth (the sum of an assumed energy absorber's thickness and the target depth in the phantom) because of the sharpness of the Bragg peak. However, even shallow targets could be successfully irradiated by employing an adequate number of paintings and by placing an energy absorber of sufficient thickness to make the effective target depth more than 12 cm. The authors also observed that motion in the beam direction was the main cause of dose distortion, followed by motion in the lateral plane perpendicular to the scan direction. Conclusions: The results suggested that by properly adjusting irradiation control parameters, gated proton spot-scanning beam therapy can be robust to target motion. This is an important first step toward establishing treatment plans in real patient geometry. (C) 2013 American Association of Physicists in Medicine.
  • Chie Toramatsu, Norio Katoh, Shinichi Shimizu, Hideaki Nihongi, Taeko Matsuura, Seishin Takao, Naoki Miyamoto, Ryusuke Suzuki, Kenneth Sutherland, Rumiko Kinoshita, Rikiya Onimaru, Masayori Ishikawa, Kikuo Umegaki, Hiroki Shirato
    RADIATION ONCOLOGY 8 48  2013年03月 [査読有り][通常論文]
     
    Background: We performed a dosimetric comparison of spot-scanning proton therapy (SSPT) and intensity-modulated radiation therapy (IMRT) for hepatocellular carcinoma (HCC) to investigate the impact of tumor size on the risk of radiation induced liver disease (RILD). Methods: A number of alternative plans were generated for 10 patients with HCC. The gross tumor volumes (GTV) varied from 20.1 to 2194.5 cm(3). Assuming all GTVs were spherical, the nominal diameter was calculated and ranged from 3.4 to 16.1 cm. The prescription dose was 60 Gy for IMRT or 60 cobalt Gy-equivalents for SSPT with 95% planning target volume (PTV) coverage. Using IMRT and SSPT techniques, extensive comparative planning was conducted. All plans were evaluated by the risk of RILD estimated using the Lyman-normal-tissue complication probability model. Results: For IMRT the risk of RILD increased drastically between 6.3-7.8 cm nominal diameter of GTV. When the nominal diameter of GTV was more than 6.3 cm, the average risk of RILD was 94.5% for IMRT and 6.2% for SSPT. Conclusions: Regarding the risk of RILD, HCC can be more safely treated with SSPT, especially if its nominal diameter is more than 6.3 cm.
  • フィルム線量解析における読取装置不安定性に起因する誤差の低減方法
    石川 正純, 小島 秀樹, 橘 英伸, 鈴木 隆介, 峯村 俊行, 遠山 尚紀, 成田 雄一郎, 西尾 禎治, 石倉 聡
    日本医学放射線学会学術集会抄録集 72回 S407 - S407 (公社)日本医学放射線学会 2013年02月
  • Jin-Min Nam, Kazi M. Ahmed, Sylvain Costes, Hui Zhang, Yasuhito Onodera, Adam B. Olshen, Kanako C. Hatanaka, Rumiko Kinoshita, Masayori Ishikawa, Hisataka Sabe, Hiroki Shirato, Catherine C. Park
    BREAST CANCER RESEARCH 15 4 2013年 [査読有り][通常論文]
     
    Introduction: Ductal carcinoma in situ (DCIS) is characterized by non-invasive cancerous cell growth within the breast ducts. Although radiotherapy is commonly used in the treatment of DCIS, the effect and molecular mechanism of ionizing radiation (IR) on DCIS are not well understood, and invasive recurrence following radiotherapy remains a significant clinical problem. This study investigated the effects of IR on a clinically relevant model of Akt-driven DCIS and identified possible molecular mechanisms underlying invasive progression in surviving cells. Methods: We measured the level of phosphorylated-Akt (p-Akt) in a cohort of human DCIS specimens by immunohistochemistry (IHC) and correlated it with recurrence risk. To model human DCIS, we used Akt overexpressing human mammary epithelial cells (MCF10A-Akt) which, in three-dimensional laminin-rich extracellular matrix (lrECM) and in vivo, form organotypic DCIS-like lesions with lumina expanded by pleiomorphic cells contained within an intact basement membrane. In a population of cells that survived significant IR doses in three-dimensional lrECM, a malignant phenotype emerged creating a model for invasive recurrence. Results: P-Akt was up-regulated in clinical DCIS specimens and was associated with recurrent disease. MCF10A-Akt cells that formed DCIS-like structures in three-dimensional lrECM showed significant apoptosis after IR, preferentially in the luminal compartment. Strikingly, when cells that survived IR were repropagated in three-dimensional lrECM, a malignant phenotype emerged, characterized by invasive activity, up-regulation of fibronectin, alpha 5 beta 1-integrin, matrix metalloproteinase-9 (MMP-9) and loss of E-cadherin. In addition, IR induced nuclear translocation and binding of nuclear factor-kappa B (NF-kappa B) to the beta 1-integrin promoter region, associated with up-regulation of alpha 5 beta 1-integrins. Inhibition of NF-kappa B or beta 1-integrin signaling abrogated emergence of the invasive activity. Conclusions: P-Akt is up-regulated in some human DCIS lesions and is possibly associated with recurrence. MCF10A-Akt cells form organotypic DCIS-like lesions in three-dimensional lrECM and in vivo, and are a plausible model for some forms of human DCIS. A population of Akt-driven DCIS-like spheroids that survive IR progresses to an invasive phenotype in three-dimensional lrECM mediated by beta 1-integrin and NF-kappa B signaling.
  • Harada K, Katoh N, Suzuki R, Inoue T, Omimaru R, Shimizu S, Miyamoto N, Ishikawa M, Shirato H
    International Journal of Radiation Oncology Biology Physics 87 2 S67  2013年 [査読有り][通常論文]
  • マルチベンダに対応した放射線治療計画管理システムの開発
    辻 真太朗, 谷川原 綾子, 鈴木 隆介, 宮崎 智夫, 藤田 勝久, 石川 正純, 白土 博樹
    医療情報学連合大会論文集 32回 1444 - 1445 (一社)日本医療情報学会 2012年11月
  • Kaneko JH, Takada E, Hara Y, Fujita F, Yamaguchi T, Kubo N, Ishikawa M, Shirato H
    PROGRESS IN NUCLEAR SCIENCE AND TECHNOLOGY 3 124 - 126 Atomic Energy Society of Japan 2012年10月 [査読有り][通常論文]
  • 宮本直樹, 石川正純, SUTHERLAND Kenneth, 鈴木隆介, 松浦妙子, 高尾聖心, 寅松千枝, 二本木英明, 清水伸一, 梅垣菊男, 白土博樹
    医学物理 Supplement 32 3 281 - 282 2012年09月13日 [査読無し][通常論文]
  • 大友可奈子, 宮本直樹, SUTHERLAND Kenneth, 鈴木隆介, 松浦妙子, 鬼丸力也, 清水伸一, 梅垣菊男, 白土博樹, 石川正純
    医学物理 Supplement 32 3 155 - 156 2012年09月13日 [査読無し][通常論文]
  • 前田憲一郎, 松浦妙子, 高尾聖心, SUTHERLAND Kenneth, 寅松千枝, 二本木英明, 宮本直樹, 石川正純, 清水伸一, 梅垣菊男, 白土博樹
    医学物理 Supplement 32 3 101 - 102 2012年09月13日 [査読無し][通常論文]
  • Taeko Matsuura, Kenichiro Maeda, Kenneth Sutherland, Taisuke Takayanagi, Shinichi Shimizu, Seishin Takao, Naoki Miyamoto, Hideaki Nihongi, Chie Toramatsu, Yoshihiko Nagamine, Rintaro Fujimoto, Ryusuke Suzuki, Masayori Ishikawa, Kikuo Umegaki, Hiroki Shirato
    MEDICAL PHYSICS 39 9 5584 - 5591 2012年09月 [査読有り][通常論文]
     
    Purpose: In accurate proton spot-scanning therapy, continuous target tracking by fluoroscopic x ray during irradiation is beneficial not only for respiratory moving tumors of lung and liver but also for relatively stationary tumors of prostate. Implanted gold markers have been used with great effect for positioning the target volume by a fluoroscopy, especially for the cases of liver and prostate with the targets surrounded by water-equivalent tissues. However, recent studies have revealed that gold markers can cause a significant underdose in proton therapy. This paper focuses on prostate cancer and explores the possibility that multiple-field irradiation improves the underdose effect by markers on tumor-control probability (TCP). Methods: A Monte Carlo simulation was performed to evaluate the dose distortion effect. A spherical gold marker was placed at several characteristic points in a water phantom. The markers were with two different diameters of 2 and 1.5 mm, both visible on fluoroscopy. Three beam arrangements of single-field uniform dose (SFUD) were examined: one lateral field, two opposite lateral fields, and three fields (two opposite lateral fields + anterior field). The relative biological effectiveness (RBE) was set to 1.1 and a dose of 74 Gy (RBE) was delivered to the target of a typical prostate size in 37 fractions. The ratios of TCP to that without the marker (TCPr) were compared with the parameters of the marker sizes, number of fields, and marker positions. To take into account the dependence of biological parameters in TCP model, alpha/beta values of 1.5, 3, and 10 Gy (RBE) were considered. Results: It was found that the marker of 1.5 mm diameter does not affect the TCPs with all alpha/beta values when two or more fields are used. On the other hand, if the marker diameter is 2 mm, more than two irradiation fields are required to suppress the decrease in TCP from TCPr by less than 3%. This is especially true when multiple (two or three) markers are used for alignment of a patient. Conclusions: It is recommended that 1.5-mm markers be used to avoid the reduction of TCP as well as to spare the surrounding critical organs, as long as the markers are visible on x-ray fluoroscopy. When 2-mm markers are implanted, more than two fields should be used and the markers should not be placed close to the distal edge of any of the beams. (c) 2012 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4745558]
  • Norio Katoh, Koichi Yasuda, Tohru Shiga, Masakazu Hasegawa, Rikiya Onimaru, Shinichi Shimizu, Gerard Bengua, Masayori Ishikawa, Nagara Tamaki, Hiroki Shirato
    INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 82 4 E671 - E676 2012年03月 [査読有り][通常論文]
     
    Purpose: We compared two treatment planning methods for stereotactic boost for treating nasopharyngeal carcinoma (NPC): the use of conventional whole-body bismuth germanate (BGO) scintillator positron emission tomography (PETCONVWB) versus the new brain (BR) PET system using semiconductor detectors (PETNEWBR). Methods and Materials: Twelve patients with NPC were enrolled in this study. [F-18]Fluorodeoxyglucose-PET images were acquired using both the PETNEWBR and the PETCONVWB system on the same day. Computed tomography (CT) and two PET data sets were transferred to a treatment planning system, and the PETCONVWB and PETNEWBR images were coregistered with the same set of CT images. Window width and level values for all PET images were fixed at 3000 and 300, respectively. The gross tumor volume (GTV) was visually delineated on PET images by using either PETCONVWB (GTV(CONV)) images or PETNEWBR (GTV(NEW)) images. Assuming a stereotactic radiotherapy boost of 7 ports, the prescribed dose delivered to 95% of the planning target volume (PTV) was set to 2000 cGy in 4 fractions. Results: The average absolute volume (+/- standard deviation [SD]) of GTV(NEW) was 15.7 ml (+/- 9.9) ml, and that of GTV(CONV) was 34.0 (+/- 20.5) ml. The average GTV(NEW) was significantly smaller than that of GTV(CONV) (p = 0.0006). There was no statistically significant difference between the maximum dose (p = 0.0585) and the mean dose (p = 0.2748) of PTV. The radiotherapy treatment plan based on the new gross tumor volume (PLAN(NEW)) significantly reduced maximum doses to the cerebrum and cerebellum (p = 0.0418) and to brain stem (p = 0.0041). Conclusion: Results of the present study suggest that the new brain PET system using semiconductor detectors can provide more accurate tumor delineation than the conventional whole-body BGO PET system and may be an important tool for functional and molecular radiotherapy treatment planning. (C) 2012 Elsevier Inc.
  • Hiroki Shirato, Rikiya Onimaru, Masayori Ishikawa, Jun-ichi Kaneko, Tsuguhide Takeshima, Kenta Mochizuki, Shinichi Shimizu, Kikuo Umegaki
    CANCER SCIENCE 103 1 1 - 6 2012年01月 [査読有り][通常論文]
     
    Respiratory motion considerably influences dose distribution, and thus clinical outcomes in radiotherapy for lung cancer. Breath holding, breath coaching, respiratory gating with external surrogates, and mathematical predicting models all have inevitable uncertainty due to the unpredictable variations of internal tumor motion. The amplitude of the same tumor can vary with standard deviations >5 mm occurring in 23% of T12N0M0 non-small cell lung cancers. Residual motion varied 16 mm (95th percentile) for the 40% duty cycle of respiratory gating with external surrogates. The 4-D computed tomography is vulnerable to problems relating to the external surrogates. Real-time 4-D radiotherapy (4DRT), where the temporal changes in anatomy during the delivery of radiotherapy are explicitly considered in real time, is emerging as a new method to reduce these known sources of uncertainty. Fluoroscopic, real-time tumor-tracking technology using internal fiducial markers near the tumor has +/- 2 mm accuracy, and has achieved promising clinical results when used with X-ray therapy. Instantaneous irradiation based on real-time verification of internal fiducial markers is considered the minimal requisite for real-time 4DRT of lung cancers at present. Real-time tracking radiotherapy using gamma rays from positron emitters in tumors is in the preclinical research stage, but has been successful in experiments in small animals. Real-time tumor tracking via spot-scanning proton beam therapy has the capability to cure large lung cancers in motion, and is expected to be the next-generation real-time 4DRT. (Cancer Sci 2012; 103: 16)
  • Katoh N, Suzuki R, Shimizu S, Inoue T, Yasuda K, Onimaru R, Kimura R, Kato M, Ishikawa M, Shirato H
    International Journal of Radiation Oncology Biology Physics 84 3 S722  2012年 [査読有り][通常論文]
  • Simulation for a Real-time Positioning System for Radiotherapy Based on Annihilation
    Junichi H. Kaneko, Eiji Takada, Yu Hara, Fumiyuki Fujita, Toru Yamaguchi, Naoki Kubo, Masayori Ishikawa, Hiroki Shirato
    Progress in Nuclear Science and Technology 3 104 - 108 2012年 [査読有り][通常論文]
     
    （全体概要）
    腫瘍に対する放射線治療の際に呼吸等によって腫瘍が移動し、治療用放射線が正常組織に照射されることがある。それを防ぐために少数の放射線検出器で腫瘍の移動を測定し、特定の位置に腫瘍があるときのみ治療用放射線を照射するシステムについて検討し、可能性を示した。
    （担当部分概要）pp.124-126
    可能性検討全般に参加した。
    （著者：Junichi H. Kaneko, Eiji Takada, Yu Hara, Fumiyuki Fujita, Toru Yamaguchi, Naoki Kubo, Masayori Ishikawa, Hiroki Shirato）
  • Naoki Miyamoto, Kenneth Sutherland, Ryusuke Suzuki, Taeko Matsuura, Chie Toramatsu, Seishin Takao, Hideaki Nihongi, Rumiko Kinoshita, Shinichi Shimizu, Rikiya Onimaru, Kikuo Umegaki, Hiroki Shirato, Masayori Ishikawa
    MEDICAL IMAGING 2012: IMAGE-GUIDED PROCEDURES, ROBOTIC INTERVENTIONS, AND MODELING 8316 2012年 [査読有り][通常論文]
     
    In the real-time tumor-tracking radiotherapy (RTRT) system, the fiducial markers are inserted in or near the target tumor in order monitor the respiratory-induced motion of tumors. During radiation treatment, the markers are detected by continuous fluoroscopy operated at 30 frames/sec. The marker position is determined by means of a template pattern matching technique which is based on the normalized cross correlation. With high tube voltage, large current and long exposure, the fiducial marker will be recognized accurately, however, the radiation dose due to X-ray fluoroscopy increases. On the other hand, by decreasing the fluoroscopy parameter settings, the fiducial marker could be lost because the effect of statistical noise is increased. In the respiratory-gated radiotherapy, the error of the image guidance will induce the reduction of the irradiation efficiency and accuracy. In order to track the marker stably and accurately in low dose fluoroscopy, we propose the application of a recursive filter. The effectiveness of the image processing is investigated by tracking the static marker and the dynamic marker. The results suggest that the stability and the accuracy of the marker tracking can be improved by applying the recursive image filter in low dose imaging.
  • Seishin Takao, Shigeru Tadano, Hiroshi Taguchi, Koichi Yasuda, Rikiya Onimaru, Masayori Ishikawa, Gerard Bengua, Ryusuke Suzuki, Hiroki Shirato
    INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 81 3 871 - 879 2011年11月 [査読有り][通常論文]
     
    Purpose: To establish a method for the accurate acquisition and analysis of the variations in tumor volume, location, and three-dimensional (3D) shape of tumors during radiotherapy in the era of image-guided radiotherapy. Methods and Materials: Finite element models of lymph nodes were developed based on computed tomography (CT) images taken before the start of treatment and every week during the treatment period. A surface geometry map with a volumetric scale was adopted and used for the analysis. Six metastatic cervical lymph nodes, 3.5 to 55.1 cm before treatment, in 6 patients with head and neck carcinomas were analyzed in this study. Three fiducial markers implanted in mouthpieces were used for the fusion of CT images. Changes in the location of the lymph nodes were measured on the basis of these fiducial markers. Results: The surface geometry maps showed convex regions in red and concave regions in blue to ensure that the characteristics of the 3D tumor geometries are simply understood visually. After the irradiation of 66 to 70 Gy in 2 Gy daily doses, the patterns of the colors had not changed significantly, and the maps before and during treatment were strongly correlated (average correlation coefficient was 0.808), suggesting that the tumors shrank uniformly, maintaining the original characteristics of the shapes in all 6 patients. The movement of the gravitational center of the lymph nodes during the treatment period was everywhere less than +/-5 mm except in 1 patient, in whom the change reached nearly 10 mm. Conclusions: The surface geometry map was useful for an accurate evaluation of the changes in volume and 3D shapes of metastatic lymph nodes. The fusion of the initial and follow-up CT images based on fiducial markers enabled an analysis of changes in the location of the targets. Metastatic cervical lymph nodes in patients were suggested to decrease in size without significant changes in the 3D shape during radiotherapy. The movements of the gravitational center of the lymph nodes were almost all less than +/-5 mm. (C) 2011 Elsevier Inc.
  • Naoki Miyamoto, Masayori Ishikawa, Gerard Bengua, Kenneth Sutherland, Ryusuke Suzuki, Suguru Kimura, Shinichi Shimizu, Rikiya Onimaru, Hiroki Shirato
    PHYSICS IN MEDICINE AND BIOLOGY 56 15 4803 - 4813 2011年08月 [査読有り][通常論文]
     
    In the real-time tumor-tracking radiotherapy system, fluoroscopy is used to determine the real-time position of internal fiducial markers. The pattern recognition score (PRS) ranging from 0 to 100 is computed by a template pattern matching technique in order to determine the marker position on the fluoroscopic image. The PRS depends on the quality of the fluoroscopic image. However, the fluoroscopy parameters such as tube voltage, current and exposure duration are selected manually and empirically in the clinical situation. This may result in an unnecessary imaging dose from the fluoroscopy or loss of the marker because of too much or insufficient x-ray exposure. In this study, a novel optimization method is proposed in order to minimize the fluoroscopic dose while keeping the image quality usable for marker tracking. The PRS can be predicted in a region where the marker appears to move in the fluoroscopic image by the proposed method. The predicted PRS can be utilized to judge whether the marker can be tracked with accuracy. In this paper, experiments were performed to show the feasibility of the PRS prediction method under various conditions. The predicted PRS showed good agreement with the measured PRS. The root mean square error between the predicted PRS and the measured PRS was within 1.44. An experiment using a motion controller and an anthropomorphic chest phantom was also performed in order to imitate a clinical fluoroscopy situation. The result shows that the proposed prediction method is expected to be applicable in a real clinical situation.
  • Shunsuke Onodera, Hidefumi Aoyama, Norio Katoh, Hiroshi Taguchi, Kouichi Yasuda, Daisuke Yoshida, Ken Surtherland, Ryusuke Suzuki, Masayori Ishikawa, Bengua Gerard, Shunsuke Terasaka, Hiroki Shirato
    JAPANESE JOURNAL OF CLINICAL ONCOLOGY 41 4 462 - 468 2011年04月 [査読有り][通常論文]
     
    Objective: To investigate the outcome of linac-based fractionated stereotactic radiotherapy over the last 10 years for intracranial skull base benign meningiomas in patients who were inoperable, who had residual tumors with some components of high mitotic index after surgery and who experienced relapse of the tumor. Methods: Twenty-seven patients with intracranial skull base benign meningiomas treated with fractionated stereotactic radiotherapy were retrospectively reviewed. Twenty-seven cases were diagnosed as benign meningiomas on pathological (17 cases) or radiological (10 cases) examination. The median follow-up time was 90 months after initial treatment and 63 months after fractionated stereotactic radiotherapy. The median biological equivalent dose calculated using an alpha/beta ratio of 2.0 Gy was 82.0 Gy (range, 60-106 Gy). Results: The 5-year overall survival was 95.7 (95% confidence interval: 87.3-100)% after initial treatment and 96.2 (88.8-100)% after fractionated stereotactic radiotherapy. The 5-year overall survival and local control rate of patients who received fractionated stereotactic radiotherapy alone were both 100%. The 5-year progression-free survival and local control rate after fractionated stereotactic radiotherapy were all 100% with a tumor volume of <9.1 cc and 68.2 (37.2-99.2) and 75.8 (45.2-100)% for the tumors 9.1 cc, respectively. The difference was significant in progression-free survival (P=0.022) and local control rate (P=0.044). The local control rate was significantly worse in patients who received fractionated stereotactic radiotherapy for relapsed tumors (P=0.01). No late radiation damage was observed in the follow-up period. Conclusions: The long-term outcome suggests that fractionated stereotactic radiotherapy is a safe and effective treatment for intracranial skull base benign meningioma, especially for those who have tumors <9.1 cc or would receive fractionated stereotactic radiotherapy with or without surgery as the initial treatment.
  • Satoshi Yamaguchi, Masayori Ishikawa, Gerard Bengua, Kenneth Sutherland, Teiji Nishio, Satoshi Tanabe, Naoki Miyamoto, Ryusuke Suzuki, Hiroki Shirato
    PHYSICS IN MEDICINE AND BIOLOGY 56 4 965 - 977 2011年02月 [査読有り][通常論文]
     
    A feasibility study of a novel PET-based molecular image guided radiation therapy (m-IGRT) system was conducted by comparing PET-based digitally reconstructed planar image (PDRI) registration with radiographic registration. We selected a pair of opposing parallel-plane PET systems for the practical implementation of this system. Planar images along the in-plane and cross-plane directions were reconstructed from the parallel-plane PET data. The in-plane and cross-plane FWHM of the profile of 2 mm diameter sources was approximately 1.8 and 8.1 mm, respectively. Therefore, only the reconstructed in-plane image from the parallel-plane PET data was used in the PDRI registration. In the image registration, five different sizes of (18)F cylindrical sources (diameter: 8, 12, 16, 24, 32 mm) were used to determine setup errors. The data acquisition times were 1, 3 and 5 min. Image registration was performed by five observers to determine the setup errors from PDRI registration and radiographic registration. The majority of the mean registration errors obtained from the PDRI registration were not significantly different from those obtained from the radiographic registration. Acquisition time did not appear to result in significant differences in the mean registration error. The mean registration error for the PDRI registration was found to be 0.93 +/- 0.33 mm. This is not statistically different from the radiographic registration which had a mean registration error of 0.92 +/- 0.27 mm. Our results suggest that m-IGRT image registration using PET-based reconstructed planar images along the in-plane direction is feasible for clinical use if PDRI registration is performed at two orthogonal gantry angles.
  • Kenneth Sutherland, Masayori Ishikawa, Gerard Bengua, Yoichi M. Ito, Yoshiko Miyamoto, Hiroki Shirato
    JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 12 3 2 - 15 2011年 [査読有り][通常論文]
     
    The purpose of this study was to evaluate a custom portal image - digitally reconstructed radiograph (DRR) registration software application. The software works by transforming the portal image into the coordinate space of the DRR image using three control points placed on each image by the user, and displaying the fused image. In order to test statistically that the software actually improves setup error estimation, an intra-and interobserver phantom study was performed. Portal images of anthropomorphic thoracic and pelvis phantoms with virtually placed irradiation fields at known setup errors were prepared. A group of five doctors was first asked to estimate the setup errors by examining the portal and DRR image side-by-side, not using the software. A second group of four technicians then estimated the same set of images using the registration software. These two groups of human subjects were then compared with an auto-registration feature of the software, which is based on the mutual information between the portal and DRR images. For the thoracic case, the average distance between the actual setup error and the estimated error was 4.3 +/- 3.0 mm for doctors using the side-by-side method, 2.1 +/- 2.4 mm for technicians using the registration method, and 0.8 +/- 0.4 mm for the automatic algorithm. For the pelvis case, the average distance between the actual setup error and estimated error was 2.0 +/- 0.5 mm for the doctors using the side-by-side method, 2.5 +/- 0.4 mm for technicians using the registration method, and 2.0 +/- 1.0 mm for the automatic algorithm. The ability of humans to estimate offset values improved statistically using our software for the chest phantom that we tested. Setup error estimation was further improved using our automatic error estimation algorithm. Estimations were not statistically different for the pelvis case. Consistency improved using the software for both the chest and pelvis phantoms. We also tested the automatic algorithm with a database of over 5,000 clinical cases from our hospital. The algorithm performed well for head and breast but performed poorly for pelvis cases, probably due to lack of contrast in the megavoltage portal image. The software incorporates an original algorithm to fuse portal and DRR images, which we describe in detail. The offset optimization algorithm used in the automatic mode of operation is also unique, and may be useful if the contrast of the portal images can be improved.
  • Miyamoto N, Ishikawa M, Bengua G, Sutherland K, Suzuki R, Kimura S, Shimizu S, Onimaru R, Shirato H
    Phys Med Biol 56 15 4803 - 13 2011年 [査読有り][通常論文]
  • Takao S, Tadano S, Taguchi H, Yasuda K, Onimaru R, Ishikawa M, Bengua G, Suzuki R, Shirato H
    Int J Radiat Oncol Biol Phys 81 3 871 - 9 2011年 [査読有り][通常論文]
  • Gerben R. Borst, Masayori Ishikawa, Jasper Nijkamp, Michael Hauptmann, Hirk Shirato, Gerard Bengua, Rikiya Onimaru, A. de Josien Bois, Joos V. Lebesque, Jan-Jakob Sonke
    INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 77 5 1596 - 1603 2010年08月 [査読有り][通常論文]
     
    Purpose: To evaluate the linear quadratic (LQ) model for hypofractionated radiotherapy within the context of predicting radiation pneumonitis (RP) and to investigate the effect if a linear (L) model in the high region (LQL model) is used. Methods and Materials: The radiation doses used for 128 patients treated with hypofractionated radiotherapy were converted to the equivalent doses given in fractions of 2 Gy for a range of alpha/beta ratios (1 Gy to infinity) according to the LQ(L) model. For the LQL model, different cut-off values between the LQ model and the linear component were used. The Lyman model parameters were fitted to the events of RP grade 2 or higher to derive the normal tissue complication probability (NTCP). The lung dose was calculated as the mean lung dose and the percentage of lung volume (V) receiving doses higher than a threshold dose of xGy (V(x)). Results: The best NTCP fit was found if the mean lung dose, or V(x), was calculated with an alpha/beta ratio of 3 Gy. The NTCP fit of other alpha/beta ratios and the LQL model were worse but within the 95% confidence interval of the NTCP fit of the LQ model with an alpha/beta ratio of 3 Gy. The V(50) NTCP fit was better than the NTCP fit of lower threshold doses. Conclusions: For high fraction doses, the LQ model with an alpha/beta ratio of 3 Gy was the best method for converting the physical lung dose to predict RP. (C) 2010 Elsevier Inc.
  • Satoru Endo, Masashi Takada, Hiroki Tanaka, Yoshihiko Onizuka, Kenichi Tanaka, Nobuyuki Miyahara, Hiromi Baba, Ayumu Oishi, Masayori Ishikawa, Masaharu Hoshi, Shinzo Kimura, Masakazu Minematsu, Yuki Morimune, Yasuaki Kojima, Kiyoshi Shizuma
    RADIATION AND ENVIRONMENTAL BIOPHYSICS 49 3 469 - 475 2010年08月 [査読有り][通常論文]
     
    This study describes measurements on secondary particles produced by a 290 MeV/n Spread Out Bragg Peak (SOBP) carbon beam. Microdosimetric distributions of secondary fragments from the SOBP carbon beam have been measured by using a new tissue equivalent proportional counter (TEPC) system at the Heavy Ion Medical Accelerator in Chiba of the National Institute of Radiological Sciences. The new TEPC system consists of a TEPC, two solid-state detectors (SSD) and a scintillation counter (FSC: forward scintillation counter). The SSDs and FSC can separately identify charged fragments and secondary neutrons produced by the incident carbon ions. Microdosimetric distributions were measured for secondary particles including neutrons produced by a body-simulated phantom consisting of various PMMA plates (thickness: 0, 34.81, 55.2, 60.95, 64.83, 95.03, 114.79, 124.69, 135.2 and 144.98 mm, respectively) to cover the SOBP (at 60-125 mm depth). The new system can separately determine produced fragments from the incident SOBP carbon beam in a body-simulated phantom.
  • Gerard Bengua, Masayori Ishikawa, Kenneth Sutherland, Kenji Horita, Rie Yamazaki, Katsuhisa Fujita, Rikiya Onimaru, Noriwo Katoh, Tetsuya Inoue, Shunsuke Onodera, Hiroki Shirato
    INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 77 2 630 - 636 2010年06月 [査読有り][通常論文]
     
    Purpose: To evaluate the effectiveness of the stereotactic body frame (SBF), with or without a diaphragm press or a breathing cycle monitoring device (Abches), in controlling the range of lung tumor motion, by tracking the real-time position of fiducial markers. Methods and Materials: The trajectories of gold markers in the lung were tracked with the real-time tumor-tracking radiotherapy system. The SBF was used for patient immobilization and the diaphragm press and Abches were used to actively control breathing and for self-controlled respiration, respectively. Tracking was performed in five setups, with and without immobilization and respiration control. The results were evaluated using the effective range, which was defined as the range that includes 95% of all the recorded marker positions in each setup. Results: The SBF, with or without a diaphragm press or Abches, did not yield effective ranges of marker motion which were significantly different from setups that did not use these materials. The differences in the effective marker ranges in the upper lobes for all the patient setups were less than 1mm. Larger effective ranges were obtained for the markers in the middle or lower lobes. Conclusion: The effectiveness of controlling respiratory-induced organ motion by using the SBF+diaphragm press or SBF + Abches patient setups were highly dependent on the individual patient reaction to the use of these materials and the location of the markers. They may be considered for lung tumors in the lower lobes, but are not necessary for tumors in the upper lobes. (C) 2010 Elsevier Inc.
  • Hiromitsu Watanabe, Megumi Toyoshima, Masayori Ishikawa, Kenji Kamiya
    ONCOLOGY REPORTS 23 5 1351 - 1360 2010年05月 [査読有り][通常論文]
     
    Experiments were conducted to assay whether monoenergetic neutron-induced genetic damage in parental germline cells can give rise to development of cancer in the offspring. Seven-week-old C3H male mice were irradiated with monoenergetic neutrons with energy levels of 0.2 or 0.6 MeV at doses of 0, 50, 100 or 200 cGy. Two weeks after irradiation, when the male mice showed an increased incidence of sperm abnormalities, they were mated with virgin 9-week-old C57BL females. Litter size was decreased and embryo lethalities were increased in a dose-dependent manner. Furthermore, tumor incidence in male offspring born to male mice irradiated with 25 or 50 cGy at 0.6 MeV showed a tendency for increase as compared to the non-irradiated group value. Liver tumors in the 50 cGy group were significantly increased (P=0.03). It is concluded that the increased hepatic tumor risk in the F, generation may have been caused by genetic transmission of some hepatoma-associated trait(s) induced by monoenergetic neutron irradiation.
  • Hee Chul Park, Shinichi Shimizu, Akio Yonesaka, Kazuhiko Tsuchiya, Yasuhiko Ebina, Hiroshi Taguchi, Norio Katoh, Rumiko Kinoshita, Masayori Ishikawa, Noriaki Sakuragi, Hiroki Shirato
    YONSEI MEDICAL JOURNAL 51 1 93 - 99 2010年01月 [査読有り][通常論文]
     
    Purpose: The purpose of this study is to evaluate the clinical results of treatment with a high dose of 3-dimensional conformal boost (3DCB) using a real-time tracking radiation therapy (RTRT) system in cervical cancer patients. Materials and Methods: Between January 2001 and December 2004, 10 patients with cervical cancer were treated with a high dose 3DCB using RTRT system. Nine patients received whole pelvis radiation therapy (RT) with a median dose of 50 Gy (range, 40-50 Gy) before the 3DCB. The median dose of the 3DCB was 30 Gy (range, 25-30 Gy). Eight patients received the 3DCB twice a week with a daily fraction of 5 Gy. The determined endpoints were tumor response, overall survival, local failure free survival, and distant metastasis free survival. The duration of survival was calculated from the time of the start of radiotherapy. Results: All patients were alive at the time of analysis and the median follow-up was 17.6 months (range, 4.9-27.3 months). Complete response was achieved in nine patients and one patient had a partial response. The 1- and 2-year local failure free survival was 78.8% and 54%, respectively. The 1- and 2-year distant metastasis free survival was 90% and 72%, respectively. Late toxicity of a grade 2 rectal hemorrhage was seen in one patient. A subcutaneous abscess was encountered in one patient. Conclusion: the use of the high dose 3DCB in the treatment of cervical cancer is safe and feasible where intracavitary brachytherapy (ICBT) is unable to be performed. The escalation of the 3DCB dose is currently under evaluation.
  • Kenneth Sutherland, Satoshi Miyajima, Hiroyuki Date, Hiroki Shirato, Masayori Ishikawa, Masao Murakami, Mitsuru Yamagiwa, Paul Bolton, Toshiki Tajima
    Radiological Physics and Technology 3 1 16 - 22 2010年01月 [査読有り][通常論文]
     
    The results of Monte Carlo calculated dose distributions of proton treatment of ocular melanoma are presented. An efficient spot scanning method utilizing active energy modulation, which also minimizes the number of target spots was developed. We simulated various parameter values for the particle energy spread and the pencil beam diameter in order to determine values suitable for medical treatment. We found that a 2.5-mm-diameter proton beam with a 5% Gaussian energy spread was suitable for treatment of ocular melanoma while preserving vision for the typical case that we simulated. The energy spectra and the required proton current were also calculated and are reported. The results are intended to serve as a guideline for a new class of low-cost, compact accelerators. © 2009 Japanese Society of Radiological Technology and Japan Society of Medical Physics.
  • Borst G. R, Ishikawa M, Nijkamp J, Hauptmann M, Shirato H, Bengua G, Onimaru R, de Josien Bois A, Lebesque J. V, Sonke J. J
    Int J Radiat Oncol Biol Phys 77 5 1596 - 603 2010年 [査読有り][通常論文]
  • Bengua G, Ishikawa M, Sutherland K, Horita K, Yamazaki R, Fujita K, Onimaru R, Katoh N, Inoue T, Onodera S, Shirato H
    Int J Radiat Oncol Biol Phys 77 2 630 - 6 2010年 [査読有り][通常論文]
  • Kentaro Nishioka, Daisuke Abo, Hidefumi Aoyama, Yasushi Furuta, Rikiya Onimaru, Shunsuke Onodera, Yutaka Sawamura, Masayori Ishikawa, Satoshi Fukuda, Hiroki Shirato
    International Journal of Radiation Oncology Biology Physics 75 5 1415 - 1419 2009年12月01日 [査読有り][通常論文]
     
    Purpose: Although the effectiveness of stereotactic radiosurgery for nonacoustic schwannomas is currently being assessed, there have been few studies on the efficacy of stereotactic radiotherapy (SRT) for these tumors. We investigated the long-term outcome of SRT for nonacoustic intracranial nerve schwannomas. Methods and Materials: Seventeen patients were treated between July 1994 and December 2006. Of these patients, 7 had schwannomas located in the jugular foramen, 5 in the trigeminal nerve, 4 in the facial nerve, and 1 in the oculomotor nerve. Radiotherapy was used as an initial treatment without surgery in 10 patients (59%) and after initial subtotal resection in the remaining patients. The tumor volume ranged from 0.3 to 31.3 mL (mean, 8.2 mL). The treatment dose was 40 to 54 Gy in 20 to 26 fractions. The median follow-up period was 59.5 months (range, 7.4-122.6 months). Local control was defined as stable or decreased tumor size on follow-up magnetic resonance imaging. Results: Tumor size was decreased in 3 patients, stable in 13, and increased in 1 after SRT. Regarding neurologic symptoms, 8 patients (47%) had improvement and 9 patients were unchanged. One patient had an increase in tumor size and received microsurgical resection at 32 months after irradiation. No patient had worsening of pre-existing neurologic symptoms or development of new cranial nerve deficits at the last follow-up. Conclusions: SRT is an effective alternative to surgical resection for patients with nonacoustic intracranial nerve schwannomas with respect to not only long-term local tumor control but also neuro-functional preservation. © 2009 Elsevier Inc. All rights reserved.
  • Development of a miniature neutron beam monitor for boron neutron capture therapy
    M., Komeda, H., Kumada, M., Ishikawa, T., Nakamura, K., Yamamoto, A., Matsumura
    Applied Radiation and Isotopes 67 254-257  Elsevier 2009年07月 [査読有り][通常論文]
  • Gerben R. Borst, Masayori Ishikawa, Jasper Nijkamp, Michael Hauptmann, Hiroki Shirato, Rikiya Onimaru, Michel M. van den Heuvel, Jose Belderbos, Joos V. Lebesque, Jan-Jakob Sonke
    RADIOTHERAPY AND ONCOLOGY 91 3 307 - 313 2009年06月 [査読有り][通常論文]
     
    Purpose: We evaluated the relationship between the mean lung dose (MLD) and the incidence of radiation pneumonitis (RP) after stereotactic body radiation therapy (SBRT), and compared this with conventional fractionated radiation therapy (CFRT). Materials and methods: For both SBRT (n=128) and CFRT (n=142) patients, RP grade >= 2 was scored. Toxicity models predicting the probability of RP as a function of the MLD were fitted Using Maximum log likelihood analysis. The MLD was NTD (Normalized Total Dose) corrected using an alpha/beta ratio of 3 Gy. Results: SBRT patients were treated with 6-12 Gy per fraction with a median MLD of 6.4 Gy (range: 1.5-6.5 Gy). CFRT patients were treated with 2 Gy or 2.25 Gy per fraction, the median MLD was 13.2 Gy (range: 3.0-23.0 Gy). The crude incidence rates of RP were 10.9% and 17.6% for the SBRT and CFRT patients, respectively. A significant close-response relationship for RP was found after SBRT, which was not significantly different from the dose-response relationship for CFRT (p = 0.18). Conclusion: We derived a significant dose-response relationship between the risk of RP and the MLD for SBRT from the clinical data. This relation was not significantly different from the dose-response relation for CFRT, although statistical analysis was hampered by the low number of patients in the high dose range. D 2009 Published by Elsevier Ireland Ltd. Radiotherapy and Oncology 91 (2009) 307-313
  • M. Ishikawa, G. Bengua, K. L. Sutherland, J. Hiratsuka, N. Katoh, S. Shimizu, H. Aoyama, K. Fujita, R. Yamazaki, K. Horita, H. Shirato
    PHYSICS IN MEDICINE AND BIOLOGY 54 7 2079 - 2092 2009年04月 [査読有り][通常論文]
     
    The purpose of this study was to develop a novel scintillation dosimeter for in vivo dosimetry in Ir-192 brachytherapy via the pulse-counting mode. The new dosimeter was made from a plastic scintillator shaped into a hemisphere of diameter 1 mm and connected to the tip of a plastic optical fiber. The relationship between pulse counts and absorbed dose was derived based on the assumption that scintillation photons from the incident gamma ray are proportional to the absorbed dose. An equation for the conversion of pulse counts to water-equivalent dose was deduced wherein the pulse height spectrum from scintillation photons was assumed to be exponential. To confirm its accuracy, the dose rate distribution in a water phantom was measured by the present dosimeter and this was compared with Monte Carlo simulations, resulting in a discrepancy of less than 1.97%. It was found that the dosimeter has a wide dynamic range of linearity up to an order of magnitude of almost 10(3), including corrections for loss of counts due to pile-up.
  • S. Shibata, K. Takamiya, Y. Ota, N. Nogawa, Y. Ito, T. Shibata, M. Hoshi, S. Endo, H. Hasai, S. Fujita
    JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY 279 2 699 - 699 2009年02月 [査読無し][通常論文]
  • Nishioka K, Abo D, Aoyama H, Furuta Y, Onimaru R, Onodera S, Sawamura Y, Ishikawa M, Fukuda S, Shirato H
    Int J Radiat Oncol Biol Phys 75 5 1415 - 9 2009年 [査読有り][通常論文]
  • Borst G. R, Ishikawa M, Nijkamp J, Hauptmann M, Shirato H, Onimaru R, van den Heuvel M. M, Belderbos J, Lebesque J. V, Sonke J. J
    Radiother Oncol 91 3 307 - 13 2009年 [査読有り][通常論文]
  • Ishikawa M, Sutherland KL, Bengua G, Suzuki R, Miyamoto N, Katoh N, Shimizu S, Onimaru R, Aoyama H, Shirato
    International Journal of Radiation Oncology Biology Physics 75 3 S590 - S591 2009年 [査読有り][通常論文]
  • Ryan McMahon, Ross Berbeco, Seiko Nishioka, Masayori Ishikawa, Lech Papiez
    MEDICAL PHYSICS 35 9 3875 - 3888 2008年09月 [査読有り][通常論文]
     
    An MLC control algorithm for delivering intensity modulated radiation therapy (IMRT) to targets that are undergoing two-dimensional (2D) rigid motion in the beam's eye view (BEV) is presented. The goal of this method is to deliver 3D-derived fluence maps over a moving patient anatomy. Target motion measured prior to delivery is first used to design a set of planned dynamic-MLC (DMLC) sliding-window leaf trajectories. During actual delivery, the algorithm relies on real-time feedback to compensate for target motion that does not agree with the motion measured during planning. The methodology is based on an existing one-dimensional (1D) algorithm that uses on-the-fly intensity calculations to appropriately adjust the DMLC leaf trajectories in real-time during exposure delivery [McMahon , Med. Phys. 34, 3211-3223 (2007)]. To extend the 1D algorithm's application to 2D target motion, a real-time leaf-pair shifting mechanism has been developed. Target motion that is orthogonal to leaf travel is tracked by appropriately shifting the positions of all MLC leaves. The performance of the tracking algorithm was tested for a single beam of a fractionated IMRT treatment, using a clinically derived intensity profile and a 2D target trajectory based on measured patient data. Comparisons were made between 2D tracking, 1D tracking, and no tracking. The impact of the tracking lag time and the frequency of real-time imaging were investigated. A study of the dependence of the algorithm's performance on the level of agreement between the motion measured during planning and delivery was also included. Results demonstrated that tracking both components of the 2D motion (i.e., parallel and orthogonal to leaf travel) results in delivered fluence profiles that are superior to those that track the component of motion that is parallel to leaf travel alone. Tracking lag time effects may lead to relatively large intensity delivery errors compared to the other sources of error investigated. However, the algorithm presented is robust in the sense that it does not rely on a high level of agreement between the target motion measured during treatment planning and delivery. (C) 2008 American Association of Physicists in Medicine.
  • Norio Katoh, Rikiya Onimaru, Yusuke Sakuhara, Daisuke Abo, Shinichi Shimizu, Hiroshi Taguchi, Yoshiaki Watanabe, Nobuo Shinohara, Masayori Ishikawa, Hiroki Shirato
    RADIOTHERAPY AND ONCOLOGY 87 3 418 - 424 2008年06月 [査読有り][通常論文]
     
    Purpose: To investigate the three-dimensional movement of internal fiducial markers near the adrenal tumors using a real-time tumor-tracking radiotherapy (RTRT) system and to examine the feasibility of high-dose hypofractionated radiotherapy for the adrenal tumors. Materials and methods: The subjects considered in this study were 10 markers of the 9 patients treated with RTRT. A total of 72 days in the prone position and 61 treatment days in the supine position for nine of the 10 markers were analyzed. All but one patient were prescribed 48 Gy in eight fractions at the isocenter. Results: The average absolute amplitude of the marker movement in the prone position was 6.1 +/- 4.4 mm (range 2.3-14.4), 11.1 +/- 7.1 mm (3.5-25.2), and 7.0 +/- 3.5 mm (3.9-12.5) in the left-right (LR), craniocaudal (CC), and anterior-posterior (AP) directions, respectively. The average absolute amplitude in the supine position was 3.4 +/- 2.9 mm (0.6-9.1), 9.9 +/- 9.8 mm (1.1-27.1), and 5.4 +/- 5.2 mm (1.7-26.6) in the LR, CC, and AP directions, respectively. Of the eight markers, which were examined in both the prone and supine positions, there was no significant difference in the average absolute amplitude between the two positions. No symptomatic adverse effects were observed within the median follow-up period of 16 months (range 5-21 months). The actuarial freedom-from-local-progression rate was 100% at 12 months. Conclusions: Three-dimensional motion of a fiducial marker near the adrenal tumors was detected. Hypofractionated RTRT for adrenal tumors was feasible for patients with metastatic tumors. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
  • Rumiko Kinoshita, Shinichi Shimizu, Hiroshi Taguchi, Norio Katoh, Masaharu Fujino, Rikiya Onimaru, Hidefumi Aoyama, Fumi Katoh, Tokuhiko Omatsu, Masayori Ishikawa, Hiroki Shirato
    INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 70 3 931 - 934 2008年03月 [査読有り][通常論文]
     
    Purpose: To evaluate the three-dimensional intrafraction motion of the breast during tangential breast irradiation using a real-time tracking radiotherapy (RT) system with a high-sampling frequency. Methods and Materials: A total of 17 patients with breast cancer who had received breast conservation RT were included in this study. A 2.0-mm gold marker was placed on the skin near the nipple of the breast for RT. A fluoroscopic real-time tumor-tracking RT system was used to monitor the marker. The range of motion of each patient was calculated in three directions. Results: The mean standard deviation of the range of respiratory motion was 1.0 +/- 0.6 mm (median, 0.9; 95% confidence interval [CI] of the marker position, 0.4-2.6), 1.3 +/- 0.5 mm (median, 1.1; 95 % CI, 0.5-2.5), and 2.6 +/- 1.4 (median, 2.3; 95 % CI, 1.0-6.9) for the right-left, craniocaudal, and anteroposterior direction, respectively. No correlation was found between the range of motion and the body mass index or respiratory function. The mean +/- standard deviation of the absolute value of the baseline shift in the right-left, craniocaudal, and anteroposterior direction was 0.2 +/- 0.2 mm (range, 0.0-0.8 mm), 0.3 +/- 0.2 mm (range, 0.0-0.7 mm), and 0.8 +/- 0.7 mm (range, 0.1-1.8 mm), respectively. Conclusion: Both the range of motion and the baseline shift were within a few millimeters in each direction. As long as the conventional wedge-pair technique and the proper immobilization are used, the intrafraction three-dimensional change in the breast surface did not much influence the dose distribution. (C) 2008 Elsevier Inc.
  • Bengua G, Ishikawa M, Sutherland K, Horita K, Yamazaki R, Fujita K, Onimaru R, Shimizu S, Shirato
    International Journal of Radiation Oncology Biology Physics 72 1 S610 - S611 2008年 [査読有り][通常論文]
  • Katoh N, Shiga T, Hasegawa M, Onimaru R, Yasuda K, Shimizu S, Bengua G, Ishikawa M, Tamaki N, Shirato
    International Journal of Radiation Oncology Biology Physics 72 1 S589 - S590 2008年 [査読有り][通常論文]
  • Satoru Endo, Masashi Takada, Yoshihiko Onizuka, Kenichi Tanaka, Naoko Maeda, Masayori Ishikawa, Nobuyuki Miyahara, Naofumi Hayabuchi, Kiyoshi Shizuma, Masaharu Hoshi
    JOURNAL OF RADIATION RESEARCH 48 5 397 - 406 2007年09月 [査読有り][通常論文]
     
    Microdosimetric single event spectra as a function of depth in a phantom for the 290 MeV/nucleon therapeutic carbon beam at HIMAC were measured by using a tissue equivalent proportional counter (TEPC). Two types of geometries were used: one is a fragment particle identification measurement (PID-mode) with time of flight (TOF) method without a backward phantom, and the other is an in-phantom measurement (IPM-mode) with a backward phantom. On the PID-mode geometry, fragments produced by carbon beam in a phantom are identified by the AE-TOF distribution between two scintillation counters positioned up- and down-stream relative to the tissue equivalent proportional counter (TEPC). Lineal energy distributions for carbon and five ion fragments (proton, helium, lithium, beryllium and boron) were obtained in the lineal-energy range of 0.1-1000 keV/gm at eight depths (7.9-147.9 mm) in an acrylic phantom. In the IPM-mode geometry, the total lineal energy distributions measured at eight depths (61.9-322.9 mm) were compared with the distributions in the PID-mode. Both spectra are consistent with each other. This shows that the PID-mode measurement can be discussed as the equivalent of the phantom measurement. The dose distribution of the carbon beam and fragments were obtained separately. In the depth dose curve, the Bragg peak was observed. Relative biological effectiveness (RBE) for the carbon beam in the acrylic phantom was obtained based on a biological response function as a lineal-energy. The RBE of carbon beam had a maximum of 4.5 at the Bragg peak. Downstream of the Bragg peak, the RBE rapidly decreases. The RBE of fragments is dominated by Boron particles around the Bragg peak region.
  • Satoru Endo, Kenichi Tanaka, Masashi Takada, Yoshihiko Onizuka, Nobuyuki Miyahara, Tatsuhiko Sato, Masayori Ishikawa, Naoko Maeda, Naofurni Hayabuchi, Kiyoshi Shizuma, Masaharu Hoshi
    MEDICAL PHYSICS 34 9 3571 - 3578 2007年09月 [査読有り][通常論文]
     
    Absorbed doses from main charged-particle beams and charged-particle fragments have been measured with high accuracy for 'particle therapy, but there are few reports for doses from neutron components produced as fragments. This study describes the measurements on neutron doses produced by carbon beams; microdosimetric distributions of secondary neutrons produced by 290 MeV/nucleon carbon beams have been measured by using a tissue equivalent proportional counter at the Heavy Ion Medical Accelerator in Chiba, Japan at the National Institute of Radiological Sciences. The microdosimetric distributions of the secondary neutron were measured on the distal and lateral faces of a body-simulated acrylic phantom (300 rum height X 300 rum width X 253 mm thickness). To confirm the dose measurements, the neutron energy spectra produced by incident carbon beams in the acrylic phantom were simulated by the particle and heavy ion transport code system. The absorbed doses obtained by multiplying the simulated neutron energy spectra with the kerma factor calculated by MCNPX agree with the corresponding experimental data fairly well. Downstream of the Bragg peak, the ratio of the neutron dose to the carbon dose at the Bragg peak was found to be a maximum of 1.4 X 10(-4) and the ratio of neutron dose was a maximum of 3.0 X 10(-7) at a lateral face of the acrylic phantom. The ratios of neutrons to charged particle fragments were 11% to 89% in the absorbed doses at the lateral and the distal faces of the acrylic phantom. We can conclude that the treatment dose will not induce serious secondary neutron effects at distances greater than 90 mm from the Bragg peak in carbon particle therapy. (c) 2007 American Association of Physicists in Medicine.
  • Hiromitsu Watanabe, Naoki Kashimoto, Junko Kajimura, Masayori Ishikawa, Kenji Kamiya
    JOURNAL OF RADIATION RESEARCH 48 3 205 - 210 2007年05月 [査読有り][通常論文]
     
    This study was undertaken to investigate induction of tumors by monoenergetic neutrons in B6C3F1 mice. Individual groups of 6 week-old animals of both sexes (about 30 mice/group) were exposed to 0.5 Gy of various monoenergetic neutrons (dose rate 0.5 cGy/min) and then observed for 13 months. The incidences of tumors (mainly liver neoplasms) in non-irradiated male and female controls were 11% and 0%, respectively. In the irradiated animals, the incidences were 53%, 50%, 60% and 43% in males, and 75%, 81%, 71%, and 85% in females, after 0.18, 0.32, 0.6 and 1.0 MeV neutron exposure, respectively. There were no significant differences in the tumor induction rate among the different energy groups.
  • Katoh N, Onimaru R, Shimizu S, Abo D, Sakuhara Y, Taguchi H, Osaka Y, Gerard B, Ishikawa M, Shirato
    International Journal of Radiation Oncology Biology Physics 69 3 S675  2007年 [査読有り][通常論文]
  • S Endo, K Tanaka, M Ishikawa, M Hoshi, Y Onizuka, M Takada, H Yamaguchi, N Hayabuchi, N Maeda, K Shizuma
    MEDICAL PHYSICS 32 12 3843 - 3848 2005年12月 [査読有り][通常論文]
     
    Microdosimetric single event spectra were determined as a function of depth in an acrylic phantom for the carbon beam at HIMAC using a tissue equivalent proportional counter (TEPC) coupled to a scintillation counter system. The fragments produced by the carbon beam were identified by the Delta E-time of flight distribution obtained from two scintillation counters which were positioned at the up- and down-stream of the TEPC. Lineal energy distribution for the carbon beam and its five fragments, namely, proton, helium, lithium, beryllium, and boron ions, were measured in the lineal-energy range of 5-1000 keV/mu m at five phantom depths between 0 and 230 mm. The dose distribution for the carbon beam and its fragments were obtained separately. The relative biological effectiveness (RBE) of the carbon beam in the phantom was calculated using a response function. The maximum RBE for the carbon beam was found to be about 5 near the Bragg peak. It was observed to rapidly decrease for Bragg peaks occurring at deeper positions in the phantom. The dose from the beam fragments accounted for about 30% to the total dose, however, its contribution to the RBE was less than 17%. (c) 2005 American Association of Physicists in Medicine.
  • M Ishikawa, H Kumada, K Yamamoto, J Kaneko, G Bengua, H Unesaki, Y Sakurai, K Tanaka, T Kosako
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 551 2-3 448 - 457 2005年10月 [査読有り][通常論文]
     
    A wide range thermal neutron detector was developed based on the Scintillator with Optical Fiber (SOF) detector which has been previously used for thermal neutron monitoring during boron neutron capture therapy irradiation. With this new detector system we intended to address the issues of real-time thermal neutron flux measurement and the simultaneous measurement of a wide range of thermal neutron flux in a BNCT irradiation field which were difficult to implement with the gold wire activation method. The dynamic range of linearity of the SOF detector was expanded by using a plastic scintillator with a rapid decay time. On the other hand, the contribution of gamma rays and fast neutrons in the measured signals were compensated from those obtained by a pair of SOF detectors, one with a (LiF)-Li-6 neutron converter and the other without. The discrimination level for the measured signals was also optimized to further reduce the contribution of gamma rays and fast neutrons signals. A non-paralyzable system model was applied to correct for the dead-time in the detector system. A good agreement between the thermal neutron flux measured by the gold wire activation method and the paired SOF detector system was observed. However, measurements which would normally take a few days to perform with the gold wire activation method were obtained in just about 15 min using the SOF detector system. We also confirmed the dynamic range of linearity for the SOF detector system to be in the order of magnitude of 10(4). (c) 2005 Elsevier B.V. All rights reserved.
  • Ishikawa M, Hirasawa M, Tomitani T, Murayama H, Hoshi M
    Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 25 1 3 - 12 1 2005年 [査読有り][通常論文]
     
    The kinematics of boron compounds in vivo is crucial to fully and safely utilize boron neutron capture therapy. In this paper, we proposed a prompt gamma-ray Compton scatter camera (PG-CSC), which can evaluate the 3-D kinematics of boron compounds without invasion. This PG-CSC combines a Compton camera with prompt gamma-ray analysis. The results of its design optimization and tests using simulations showed that one-hour-measurement was sufficient to evaluate a 3-D boron concentration distribution in a rat's brain with the resolution of 1mm in FWHM.
  • Hisako Niko, Hiroyuki Takahashi, Kaoru Fujita, Masaharu Nakazawa, Masayori Ishikawa, Michihiro Furusaka, Takashi Ino, Masakazu Kanazawa
    IEEE Nuclear Science Symposium Conference Record 2 1205 - 1207 2005年 [査読有り][通常論文]
     
    Now we are developing a very large area position-sensitive neutron detector for a next generation Japanese spallation neutron source, J-PARC. Recently, we have proposed a new Global-Local Grouping method to reduce the scale of front-end electronics for two-dimensional microstrip gas chambers. In this method we divide a signal charge into two parts: one provides a coarse position and the other provides a fine position. The method relies on a multi-layer microfabrication technique but we could successfully confirm the principle of this encoding method. In this paper, we propose another variation of the Global-Local Grouping method which utilizes a geometrical charge division method for cathode signals. Basically, positive ions created near an anode strip are split in neighboring two cathode strips. In this method we can improve the position resolution to -10 times at the signal noise ratio of 40. We have fabricated an ultra-long microstrip detector whose sensitive length was 640 mm. Test measurement with 8keV X-rays provided a fine position resolution of 1-3mm. We could successfully demonstrated the principle of our method. ©2005 IEEE.
  • Masayori Ishikawa, Hiroaki Kumada, Kazuyoshi Yamamoto, Junichi H. Kaneko, Hiroyuki Takahashi
    IEEE Nuclear Science Symposium Conference Record 5 2917 - 2919 2005年 [査読有り][通常論文]
     
    Recently, a new type of detector using a scintillator coupled with an optical fiber was developed for the same purpose. Among these types of detectors, the SOF (Scintillator with Optical Fiber) detector has been used for monitoring thermal neutron during boron neutron capture therapy in Japan. The detector probe of the SOF detector system is smaller than other neutron monitors such as gas counters which makes the SOF detector more useful for thermal neutron monitoring in restricted spaces. A phantom experiment was performed using the SOF detector to test the applicability for a boron neutron capture therapy irradiation field study. The result measured by the SOF detector agrees well with a gold wire measurement in spite of only a 30-minutes measurement time with the SOF detector. © 2005 IEEE.
  • 中性子捕捉療法のための熱中性子リアルタイムモニタの開発
    石川正純, 熊田博明, 小野公二, 櫻井良憲, 町島祐一, 高橋浩之
    Ionizing Radiation 31 4 279 - 286 2005年 [査読有り][通常論文]
  • Nireka Adachi, Masayori Ishikawa, Koichi E. Okamoto
    GAMING, SIMULATIONS, AND SOCIETY 149 - 158 2005年 [査読有り][通常論文]
  • Hisako Niko, Hiroyuki Takahashi, Kaoru Fujita, Masaharu Nakazawa, Masayori Ishikawa, Michihiro Furusaka, Takashi Ino, Masakazu Kanazawa
    2005 IEEE Nuclear Science Symposium Conference Record, Vols 1-5 1205 - 1207 2005年 [査読有り][通常論文]
     
    Now we are developing a very large area position-sensitive neutron detector for a next generation Japanese spallation neutron source, J-PARC. Recently, we have proposed a new Global-Local Grouping method to reduce the scale of front-end electronics for two-dimensional microstrip gas chambers. In this method we divide a signal charge into two parts: one provides a coarse position and the other provides a fine position. The method relies on a multi-layer microfabrication technique but we could successfully confirm the principle of this encoding method. In this paper, we propose another variation of the Global-Local Grouping method which utilizes a geometrical charge division method for cathode signals. Basically, positive ions created near an anode strip are split in neighboring two cathode strips. In this method we can improve the position resolution to similar to 10 times at the signal noise ratio of 40. We have fabricated an ultra-long microstrip detector whose sensitive length was 640 mm. Test measurement with 8keV Xrays provided a fine position resolution of 1-3mm. We could successfully demonstrated the principle of our method.
  • Masayori Ishikawa, Hiroaki Kumada, Kazuyoshi Yamamoto, Junichi H. Kaneko, Hiroyuki Takahashi
    2005 IEEE Nuclear Science Symposium Conference Record, Vols 1-5 5 2917 - 2919 2005年 [査読有り][通常論文]
     
    Recently, a new type of detector using a scintillator coupled with an optical fiber was developed for the same purpose. Among these types of detectors, the SOF (Scintillator with Optical Fiber) detector has been used for monitoring thermal neutron during boron neutron capture therapy in Japan. The detector probe of the SOF detector system is smaller than other neutron monitors such as gas counters which makes the SOF detector more useful for thermal neutron monitoring in restricted spaces. A phantom experiment was performed using the SOF detector to test the applicability for a boron neutron capture therapy irradiation field study. The result measured by the SOF detector agrees well with a gold wire measurement in spite of only a 30-minutes measurement time with the SOF detector.
  • M Ishikawa, K Ono, Y Sakurai, H Unesaki, A Uritani, G Bengua, T Kobayashi, K Tanaka, T Kosako
    APPLIED RADIATION AND ISOTOPES 61 5 775 - 779 2004年11月 [査読有り][通常論文]
     
    A new thermal neutron monitor for boron neutron capture therapy was developed in this study. We called this monitor equipped boron-loaded plastic scintillator that uses optical fiber for signal transmission as an [scintillator with optical fiber] SOF detector. A water phantom experiment was performed to verify how the SOF detector compared with conventional method of measuring thermal neutron fluence. Measurements with a single SOF detector yielded indistinguishable signals for thermal neutrons and gamma rays. To account for the gamma ray contribution in the signal recorded by the SOF detector, a paired SOF detector system was employed. This was composed of an SOF detector with boron-loaded scintillator and an SOF detector with a boron-free scintillator. The difference between the recorded counts of these paired SOF detectors was used as the measure of the gamma ray contribution in the measured neutron fluence. The paired SOF detectors were ascertained to be effective in measuring thermal neutron flux in the range above 10(6) (n/cm(2)/s). Clinical trials using paired SOF to measure thermal neutron flux during therapy confirmed that paired SOF detectors were effective as a real-time thermal neutron flux monitor. (C) 2004 Elsevier Ltd. All rights reserved.
  • Upgrade of scintillator with optical fiber detector for real-time neutron flux monitor using compensation of gamma-ray and dead-time correction
    M. Ishikawa, K. Ono, H. Unesaki, T. Kobayashi, Y. Sakurai, K. Tanaka, T. Kosako
    KURRI Progress Report 126-  2004年 [査読有り][通常論文]
  • セミパラチンスクの核実験場近郊住民の放射線影響
    星 正治, 高田 純, 金 隆史, 石川 正純, 川野 徳幸, 峠岡 康幸, 新田 由美子, イリダナ・テレウハン, 岡本 哲治, 武市 宣雄, 山田 英雄, ヴァレリ・ステパネンコ, 早川 式彦, 木村 昭郎, 山本 政儀, 吉川 勲, 高辻 俊宏, ナイラ・チャイジュヌソバ, カズベック・アプサリコフ, ボリス・グシェフ, ムラト・テレウオフ, ザクシバ・ズマジーロフ, 片山 博昭, 豊田 新
    広島大学原爆放射線医科学研究所年報 44 141 - 141 広島大学原爆放射線医科学研究所 2003年09月
  • K Shizuma, S Endo, M Hoshi, J Takada, M Ishikawa, K Iwatani, H Hasai, T Oka, S Fujita, T Watanabe, T Yamashita, T Imanaka
    JOURNAL OF RADIATION RESEARCH 44 2 133 - 139 2003年06月 [査読有り][通常論文]
     
    Residual Eu-152 activities induced by neutrons from the Nagasaki atomic bomb were measured for nine mineral samples located up to 1,061 in in the slant range and one control sample at 2,850 in from the hypocenter. A chemical separation to prepare europium-enriched samples was performed for all samples, and gamma ray measurements were carried out with a low background well-type germanium detector. In this paper, the measured specific activities of Eu-152 are compared with activation calculations based on the DS86 neutron fluence and the 93Rev one. The calculated-to-measured ratios are also compared with those of Co-60 and Cl-36. The present results indicate that the measurements agree to the calculation within a factor of three as observed in the nuclear tests at Nevada. The activation level of environmental neutrons and the detection limit for Eu-152 are also discussed.
  • W Zhang, K Fujikawa, S Endo, M Ishikawa, M Ohtaki, H Ikeda, M Hoshi
    JOURNAL OF RADIATION RESEARCH 44 2 171 - 177 2003年06月 [査読有り][通常論文]
     
    The relative biological effectiveness (RBE) of various energy neutrons produced from a Schenkel-type accelerator at the Research Institute for Radiation Biology and Medicine, Hiroshima University (HIRRAC), compared with Co-60 gamma-ray radiation was determined. The neutron radiations and gamma-ray radiation produced good linear changes in the frequency of micronuclei induced in the root-tip cells of Allium cepa onion irradiated as dry dormant seeds (seed assay) and seedlings (seedling assay) with varying radiation doses. Therefore the RBE for radiation-induced micronuclei can be calculated as the ratio of the slopes of the fitted linear dose response for the neutron radiations and the Co-60 gamma-ray radiation. The RBE values by seed assay and seedling assay decreased to 174 +/- 7, from 216 +/- 9, and to 31.4 +/- 1.0, from 45.3 +/- 1.3 (one standard error), respectively, when neutron energies increased to 1.0 MeV, from 0.2 MeV, in the present study. Furthermore, the ratio of the micronucleus induction rates of seed assay to seedling assay by gamma-ray radiation was much lower than that by neutron radiations.
  • Development of real-time thermal neutron flux monitor during boron neutron capture therapy
    M. Ishikawa, K. Ono, H. Unesaki, T. Kobayashi, Y. Sakurai, K. Tanaka, T. Kosako
    KURRI Progress Report 140  2003年04月
  • Y. Onizuka, S. Endo, M. Ishikawa, M. Hoshi, S. Sakurai, T. Kobayashi, H. Utsumi, N. Hayabuchi, T. Takatsuji, H. Yamaguchi, M. Takada, K. Fujikawa, N. Maeda, K. Tanaka
    KURRI Progress Report 122  2003年04月01日 [査読無し][通常論文]
  • S Endo, E Yoshida, Y Yoshitake, T Horiguchi, WY Zhang, K Fujikawa, M Hoshi, T Itoh, M Ishikawa, K Shizuma
    JOURNAL OF RADIATION RESEARCH 43 4 381 - 386 2002年12月 [査読有り][通常論文]
     
    The energy spectrum of fission neutrons in the biological irradiation field of the Kinki University reactor, UTR-KINKI, has been determined by a multi-foil activation analysis coupled with artificial neural network techniques and a Au-foil activation method. The mean neutron energy was estimated to be 1.26 +/- 0.05 MeV from the experimentally determined spectrum. Based on this energy value and other information, the neutron dose rate was estimated to be 19.7 +/- 1.4 cGy/hr. Since this dose rate agrees with that measured by a pair of ionizing chambers (21.4 cGy/hr), we conclude that the mean neutron energy could be estimated with reasonable accuracy in the irradiation field of UTR-KINKI.
  • WY Zhang, S Endo, M Ishikawa, H Ikeda, M Hoshi
    JOURNAL OF RADIATION RESEARCH 43 4 397 - 403 2002年12月 [査読有り][通常論文]
     
    The relative biological effectiveness (RBE) of mixed neutron and gamma-ray radiation emitted at a Cf-252 source at the Research Institute for Radiation Biology and Medicine, Hiroshima University, compared with Co-60 gamma-ray radiation was determined. The tissue-absorbed dose contribution of the accompanying gamma radiation was about 35.7% to the total tissue-absorbed dose from the Cf-252 mixed radiation. The Cf-252 mixed radiation and Co-60 gamma rays produced approximate linear changes in the frequency of micronuclei induced in root-tip cells of Allium cepa L. onion seedlings after irradiation as dry dormant seeds with varying absorbed doses in onion seeds. Therefore, the RBE for radiation-induced micronuclei was calculated as the ratio of the slopes for the Cf-252 mixed radiation and the Co-60 gamma rays. The deduced RBE value of Cf-252 mixed radiation to Co-60 gamma rays to induce micronuclei in dry dormant onion seed cells was about 90.5 +/- 3.6 (+/- 1sigma); the RBE of neutrons from the Cf-252 mixed radiation was about 150 +/- 6 (+/- 1sigma). Furthermore, the sensitivity ratio of the induction rate of micronuclei in dry dormant seeds to that in seedlings by neutrons from Cf-252 mixed radiation was significantly different from that by Co-60 gamma rays. From these results, we concluded that the repair efficiency of DNA damage induced by neutrons may be different from that by gamma rays.
  • K Tanaka, T Kobayashi, Y Sakurai, Y Nakagawa, M Ishikawa, M Hoshi
    PHYSICS IN MEDICINE AND BIOLOGY 47 16 3011 - 3032 2002年08月 [査読有り][通常論文]
     
    A calculation method for the dosage of neutrons by near-threshold Li-7(p, n)Be-7 and gamma rays by Li-7(p, p'gamma)Li-7 was validated through experiments with variable distance between the Li target and the phantom, focusing on large angular dependence. The production of neutrons and gamma rays in the Li target was calculated by Lee's method and their transport in the phantom was calculated using the MCNP-4B code. The dosage in intra-operative boron neutron capture therapy (BNCT) using near-threshold Li-7(p, n)Be-7 direct neutrons was evaluated using the validated calculation method. The effectiveness of the usage of the direct neutrons was confirmed from the existence of the region satisfying the requirements of the protocol utilized in intra-operative BNCT for brain tumours in Japan. The boron-dose enhancer (BDE) introduced in this paper to increase the contribution of the B-10(n, alpha)Li-7 dose in the living body was effective. The void utilized to increase the dose in deep regions was also effective with BDE. For the investigation of 1.900 MeV proton beams, for example, it was found that intra-operative BNCT using near-threshold Li-7(p, n)Be-7 direct neutrons is feasible.
  • RO Suzuki, M Ishikawa, K Ono
    JOURNAL OF ALLOYS AND COMPOUNDS 336 1-2 280 - 285 2002年04月 [査読有り][通常論文]
     
    For obtaining better oxidation resistance of niobium in air, a niobium silicide was non-electrolytically deposited onto niobium from the molten salt, where a disproportional reaction occurs between Na2SiF6, SiO2, and Si. A single phase of NbSi, was formed with a homogeneous thickness of about 10 mum above 1073 K. The oxidation resistance of pure niobium with this coating layer was improved. During the oxidation at the high temperatures, Nb5Si3 was formed at the interface between the Nb substrate and the NbSi2 layer. Due to this intermediate layer formation, the oxidation resistance became better than for pure NbSi2. (C) 2002 Elsevier Science BY All fights reserved.
  • K Tanaka, T Kobayashi, Y Nakagawa, Y Sakurai, M Ishikawa, M Hoshi
    RESEARCH AND DEVELOPMENT IN NEUTRON CAPTURE THERAPY 213 - 219 2002年 [査読有り][通常論文]
     
    A calculation method for the dosage of neutrons by near-threshold Li-7(p,n)(7) Be and gamma rays by Li-7(p,p'gamma)Li-7 was validated through experiments with variable distance between the Li target and the phantom focusing on large angular dependence. By the dosage evaluation using the validated calculation method, a boron-dose enhancer (BDE) introduced in this study to increase B-10(n,alpha)Li-7 dose in a living body was effective. The void used to increase doses in deep regions was also valid with the BDE. The region satisfying the requirements of the protocol in intra-operative BNCT for brain tumors in Japan was acknowledged to be comparable to present BNCT, for the proton energy of 1.900 MeV for example. It was found that intra-operative BNCT using near-threshold Li-7(p,n)Be-7 direct neutrons is feasible.
  • M Ishikawa, N Unesaki, T Kobayashi, Y Sakurai, K Tanaka, S Endo, M Hoshi
    RESEARCH AND DEVELOPMENT IN NEUTRON CAPTURE THERAPY 443 - 447 2002年 [査読有り][通常論文]
     
    We developed a new thermal neutron fluence detector for Boron Neutron Capture Therapy using plastic optical fiber with plastic scintillator containing Boron-10. The presented detector has quite low sensitivity for gammarays, and we succeeded measuring thermal neutrons accurately.
  • The Feasibility of Intra-Operative BNCT using Near-Threshold 7Li(p、n)7Be Direct Neutrons
    T.Kobayashi, K.Tanaka, Y.Sakurai, Y.Nakagawa, M.Ishikawa, M.Hoshi
    KURRI Prog. Rep 2001 166 - 0 2002年 [査読無し][通常論文]
  • The Validation of the Simulation Calculation Method for the Near-threshold 7Li(p、n)7Be and 7Li(p、p’g)7Li Reactions in BNCT
    T.Kobayashi, K.Tanaka, Y.Sakurai, Y.Nakagawa, M.Ishikawa, M.Hoshi
    KURRI Prog. Rep 2001 167 - 0 2002年 [査読無し][通常論文]
  • M Ishikawa, T Kobayashi, Y Sakurai, K Kanda
    JOURNAL OF RADIATION RESEARCH 42 4 387 - 400 2001年12月 [査読有り][通常論文]
     
    Because background radiation in an irradiation room creates a problem with the PG-SPECT (Prompt Gamma-ray Single Photon Emission Computed Tomography) system, which evaluates the absorbed dose for the Boron Neutron Capture Therapy treatment, optimization of a collimator system was performed while taking the shielding of background gamma-rays into consideration. Assuming that a parallel-beam collimator is used, three parameters - the diameter of a hole, the length of the collimator, and the number of detectors (the number of holes of the collimator) - were selected for optimization. Because the combinations of these parameters are limitless, it is difficult to determine them simultaneously. Therefore, a statistically derived Optimization Criterion has been proposed to optimize these parameters. When the spatial resolution was 1 cm-FWHM (full width at half maximum), the optimal diameter of the collimator was 5.4 mm, the optimal length was 321 mm, and the optimal number of detectors was 31 x 31.
  • M Ishikawa, T Kobayashi, K Kanda
    FRONTIERS IN NEUTRON CAPTURE THERAPY, VOLS 1 AND 2 1145 - 1149 2001年 [査読有り][通常論文]
  • T Kobayashi, Y Sakurai, M Ishikawa
    FRONTIERS IN NEUTRON CAPTURE THERAPY, VOLS 1 AND 2 641 - 645 2001年 [査読有り][通常論文]
  • M Ishikawa, T Kobayashi, K Kanda
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 453 3 614 - 620 2000年10月 [査読有り][通常論文]
     
    In order to reduce the standard deviation in counting prompt gamma -rays emitted from B-10(n,alpha gamma)Li-7 reactions at Prompt Gamma-ray Single Photon Emission Computed Tomography (PG-SPECT) system, statistical estimation using a Maximum Likelihood Estimation (MLE) is proposed. The measured energy spectrum was analyzed statistically with MLE based on the ideal energy spectrum. The standard deviation of counting was estimated using 20000 energy spectra including background gamma -rays, generated with a Monte Carlo method on a personal computer. When the SIN ratio is lower than 0.1, the standard deviation of the method presented here, i.e. the Maximum Likelihood Estimation of Spectrum (MLES). was reduced by up to approximately 20% compared to the conventional Triple Energy Window (TEW) method. (C) 2000 Elsevier Science B.V. All rights reserved.
  • T Kobayashi, Y Sakurai, M Ishikawa
    MEDICAL PHYSICS 27 9 2124 - 2132 2000年09月 [査読有り][通常論文]
     
    A noninvasive method for measuring the absorbed dose distribution during the administration of clinical boron neutron capture therapy (BNCT) using an online three-dimensional (3D) imaging system is presented. This system is designed to provide more accurate information for treatment planning and dosimetry. The single-photon emission computed tomography (SPECT) technique is combined with prompt gamma-ray analysis (PGA) to provide an ideal dose estimation system for BNCT. This system is termed PC-SPECT. The fundamental feasibility of the PC-SPECT system for BNCT is confirmed under the following conditions: (1) a voxel size of 1x1x1 cm(3), comparable to the spatial resolution of our standard dosimetric technique using gold wire activation, where data are available for every 5-10 mm of wire length; (2) a reaction rate of (10)B(n,alpha)(7)Li within the measurement volume is greater than 1.1x10(6) interactions/cm(3)/s, corresponding to a thermal neutron flux of 5 x 10(8) n/cm(2)/s and a (10)B concentration of greater than 10 ppm For the deepest part of the tumor volume under typical BNCT clinical conditions; (3) statistical uncertainty of the count rate for (10)B(n, alpha)(7)Li prompt gamma rays is 10% or less. The desirable characteristics of a detector for the PG-SPECT system were determined by basic experiments using both HPGe and CdTe semiconductor detectors. The CdTe semiconductor detector has the greatest potential fur this system because of its compactness and simplicity of maintenance. (C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)00509-5].
  • Electroless Coating of Fe3Si on Steels in the Moleten Salt
    R. O. Suzuki, T. Nishibata, Y. Nagaso, K. Nakanishi, M. Ishikawa, K. Teranuma, K. Ono
    Fluxes and Salts 12 - 17 2000年06月 [査読無し][通常論文]
     
    Proc. of 6th Intern. Conf. on Molten Slags, Fluxes and Salts, (12-17 June 2000,
    Stockholm, Sweden and Helsinki, Finland), ed. by S. Seetharaman and D. Sichen, paper 180.
  • RO Suzuki, M Ishikawa, K Ono
    JOURNAL OF ALLOYS AND COMPOUNDS 306 1-2 285 - 291 2000年06月 [査読有り][通常論文]
     
    For obtaining oxidation resistance of molybdenum in air, molybdenum silicide was non-electrolytically coated in the molten salt, where a disproportion reaction occurs between the salt composed of NaCl-KCl-NaF-Na2SiF6-SiO2 and the Si powder. Hexagonal MoSi2 was formed as single phase with homogeneous thickness of tens of mu m above 1073 K, while the tetragonal MoSi2 phase was additionally formed at 973 K. The growth rate of the MoSi2 layer and its morphology at the sample corner were affected by this phase formation. The protective layer on the siliconized sample proved to be effective for preventing oxidation that occurs for pure molybdenum at low temperatures. During the oxidation at the high temperature, Mo5S3 was formed at the interface between the Mo substrate and the MoSi2 layer. (C) 2000 Elsevier Science S.A. All rights reserved.
  • RO Suzuki, T Nishibata, K Nakanishi, M Ishikawa, K Ono
    STEEL RESEARCH 71 4 130 - 137 2000年04月 [査読有り][通常論文]
     
    The corrosion-resistive intermetallic compound Fe3Si could non-electrolytically coat pure iron and mild steel. The disproportional reaction between Si and Si4+ ions deposited the homogeneous Fe3Si layer on the Fe substrates, by using solid silicon and the molten salt composed of NaCl-KCl-NaF-Na2SiF6-SiO2. SiF4 gas evaporation prevented from continuous siliconization, when only Na2SiF6 was used as Si4+ ion source. By adding SiO2 into the salt as another source, the molten salt became endurable for repeated usage in air. The layer of Fe3Si single phase with silicon mole fractions of 24 +/- 1 % grew thicker than 200 mu m by immersing for a few hours at 973 - 1173K.
  • 高辻俊宏, 吉川 勲, 星 正治, 高田 純, 遠藤 暁, 石川正純
    Space Utilization Research 16 33 - 36 2000年 [査読無し][通常論文]
  • On-line Absorbed Dose Estimation System for BNCT by PG-SPECT
    T.Kobayashi, Y.Sakurai, M.Ishikawa
    KURRI Prog. Rep 1999 179 - 0 2000年 [査読無し][通常論文]
  • Survey of external dose around the JCO facility using sugar samples and ESR method
    Shiraishi, K, Kimura, S, Honehara, H, Takada, J, Ishikawa, M, Igarashi, Y, Aoyama, M, Komura, K, Nakajima, T
    Adv. ESR Appl. 16 9 - 14 2000年 [査読有り][通常論文]

MISC

  • 櫻井良憲, 渡辺賢一, 吉橋幸子, 増田明彦, 石川正純, 納冨昭弘, 村田勲, 遠藤暁, 田中憲一, 宇野彰二, 眞正浄光, 笈田将皇, 林慎一郎, 田中浩基, 黒澤俊介, 谷森達, 高田淳史, 中村哲志, 高田卓志, 加茂前健, 道上宏之, 保田浩志, 黒木伸一郎, 井川和代 KURNS-EKR (Web) (17) 2023年
  • 櫻井良憲, 瓜谷章, 石川正純, 納冨昭弘, 遠藤暁, 田中憲一, 眞正浄光, 笈田将皇, 林慎一郎, 田中浩基, 黒澤俊介, 谷森達, 中村哲志, 高田卓志, 保田浩志, 宇野彰二, 道上宏之, 村田勲 KURNS-EKR (Web) (6) 2020年
  • 玉利勇樹, 高田卓志, 栗原孝太, 石川正純, LEE Sutherland Kenneth, 櫻井良憲, 田中浩基, 鈴木実 日本放射線腫瘍学会高精度放射線外部照射部会学術大会プログラム・抄録集 32nd 2019年
  • 石川正純 IVR 32 (4) 299‐305 2018年01月30日 [査読無し][通常論文]
  • 石川正純 臨床放射線 62 (2) 257‐263 2017年02月10日 [査読無し][通常論文]
  • 石川 正純 臨床放射線 62 (2) 257 -263 2017年02月 [査読無し][通常論文]
  • Masayori Ishikawa, Shubhechha J. Shrestha Image-Based Computer-Assisted Radiation Therapy 273 -292 2017年01月01日 [査読無し][通常論文]
     
    In radiotherapy practice, the planning target volume (PTV) must include larger margin for moving tumor compared to tumors at rest with same clinical target volume (CTV). In order to avoid normal tissue complications, organ motion should either be freezed relative to treatment beam or the tumor must be tracked in a real time. The real-time tracking of the tumor can reduce the tumor motion margin in the dose distribution, sparing the healthy tissues near the tumor. Several methods have been proposed for tracking the tumor in a real time. The most widely used method is external surrogate system, where the tumor position is based on external surrogates, such as the abdomen that expands and contracts as the patient breathes. Gold fiducials are also used as a surrogate marker because it is easily detectable in the fluoroscopic image allowing the continuous monitoring of the tumor. In this chapter, recent techniques will be introduced with their benefits and limitations.
  • R. Ogawara, M. Ishikawa REVIEW OF SCIENTIFIC INSTRUMENTS 87 (7) 2016年07月 [査読無し][通常論文]
     
    The anode pulse of a photomultiplier tube (PMT) coupled with a scintillator is used for pulse shape discrimination (PSD) analysis. We have developed a novel emulation technique for the PMT anode pulse based on optical photon transport and a PMT response function. The photon transport was calculated using Geant4 Monte Carlo code and the response function with a BC408 organic scintillator. The obtained percentage RMS value of the difference between the measured and simulated pulse with suitable scintillation properties using GSO:Ce (0.4, 1.0, 1.5 mol%), LaBr3:Ce and BGO scintillators were 2.41%, 2.58%, 2.16%, 2.01%, and 3.32%, respectively. The proposed technique demonstrates high reproducibility of the measured pulse and can be applied to simulation studies of various radiation measurements. (C) 2016 Author(s).
  • 宮本直樹, 石川正純, 井上哲也, 加藤徳雄, 清水伸一, 鬼丸力也, 白土博樹 臨床放射線 61 (2) 293‐302 2016年02月10日 [査読無し][通常論文]
  • 宮本 直樹, 石川 正純, 井上 哲也 臨床放射線 61 (2) 293 -302 2016年02月 [査読無し][通常論文]
  • N. Miyamoto, M. Ishikawa, R. Suzuki, A. Makinaga, T. Matsuura, S. Takao, Y. Matsuzaki, T. Inoue, N. Katoh, S. Shimizu, R. Onimaru, H. Shirato INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 93 (3) E554 -E554 2015年11月 [査読無し][通常論文]
  • 新規動体追跡技術により可能になる3D imagingによる自由行動マウスの全身の遺伝子発現追跡定量法の開発
    浜田 俊幸, 石川 正純, Sutherland Kenneth, 宮本 直樹, 白土 博樹, 本間 さと, 本間 研一 バイオイメージング 24 (2) 114 -114 2015年09月 [査読無し][通常論文]
  • Rikiya Onimaru, Shinichi Shimizu, Hiroki Shirato, Masayori Ishikawa Stereotactic Body Radiation Therapy: Principles and Practices 217 -224 2015年08月06日 [査読無し][通常論文]
  • R. Ogawara, M. Ishikawa Review of Scientific Instruments 86 (8) 2015年08月01日 [査読無し][通常論文]
     
    A novel analysis method named peak-to-charge ratio (V< inf> p< /inf> /Q< inf> total< /inf> ) discrimination, aiming at background rejection especially for alpha decay self-activity in LaBr< inf> 3< /inf> : Ce scintillators has been developed. This method is based on a waveform analysis using the peak-to-charge ratio in the output waveform of a photomultiplier tube. The discrimination of alpha-induced events was achieved by using a threshold function based on the error propagation of the V< inf> p< /inf> /Q< inf> total< /inf> value. The accidental rejection ratio of gamma-induced events was evaluated to be 0.17%. Furthermore, a total absorption peak spectrum processed with the V< inf> p< /inf> /Q< inf> total< /inf> discrimination method for < sup> 68< /sup> Ga 1.883 MeV gamma rays, where the energy was overlapped with background alpha events, reproduced exactly the same result as that of the background subtraction method. The difference in measured peak counts of both methods was 0.716%, and the statistical error in the V< inf> p< /inf> /Q< inf> total< /inf> discrimination method and background subtraction was 4.81% and 8.70%, respectively. Thus a higher-accuracy measurement could be achieved using the V< inf> p< /inf> /Q< inf> total< /inf> discrimination method. The present study demonstrates that the V< inf> p< /inf> /Q< inf> total< /inf> discrimination method is a promising method for background rejection of the spontaneous alpha decay in LaBr< inf> 3< /inf> : Ce scintillators.
  • 新規4D imagingによる自由行動マウスの全身の時計遺伝子発現制御機構の解析
    浜田 俊幸, Sutherland Kenneth, 石川 正純, 宮本 直樹, 本間 さと, 白土 博樹, 本間 研一 日本薬学会年会要旨集 135年会 (2) 290 -290 2015年03月 [査読無し][通常論文]
  • SOF検出器によるBNCT治療中のリアルタイム熱中性子モニタリング
    石川正純, 小野公二, 松村 明, 平塚純一, 宮武伸一, 櫻井良憲, 熊田博明 日本放射線腫瘍学会 第27回学術大会 O-074 (2014.12.11-13) 横浜 2014年12月 [査読無し][通常論文]
  • 小島秀樹, 瀧上誠, 水野文弥, 浅野友洋, 黒澤亮輔, 猪俣淳二, 石川正純 日本放射線技術学会雑誌 70 (9) 1020 2014年09月20日 [査読無し][通常論文]
  • 天井克生, 石川正純 日本放射線技術学会雑誌 70 (9) 987 2014年09月20日 [査読無し][通常論文]
  • 石川正純 Isot News (725) 15 -18 2014年09月01日 [査読無し][通常論文]
  • リアルタイム熱中性子束モニタの開発と臨床応用
    石川正純, 小野公二, 松村 明, 山本哲哉, 平塚純一, 宮武伸一, 加藤逸郎, 櫻井良憲, 古林 徹, 熊田博明 日本中性子捕捉療法学会 第11回学術大会 一般演題34 (2014.07.05-06) 吹田 2014年07月 [査読無し][通常論文]
  • 宮本直樹, 石川正純, 井上哲也, 加藤徳雄, 清水伸一, 鬼丸力也, 白土博樹 Rad Fan 12 (3) 70-73,20 2014年02月25日 [査読無し][通常論文]
  • 吉村 高明, 安田 耕一, 寅松 千枝, 高尾 聖心, 松浦 妙子, 二本木 英明, 木下 留美子, 鬼丸 力也, 白土 博樹, 石川 正純 Japanese Journal of Radiology 32 (Suppl.) 7 -7 2014年02月 [査読無し][通常論文]
  • 石川正純, 松浦妙子, 作原祐介, 阿保大介, 中川啓治, 古畑優 IVR 28 (4) 485 -485 2013年10月01日 [査読無し][通常論文]
  • 放射線照射後の乳癌再発に関わるシグナルの解析(Possible mechanisms of non-invasive to invasive phenotypic conversion of breast cancer cells upon radiation)
    南 ジンミン, 小野寺 康仁, 石川 正純, 佐邊 壽孝, 白土 博樹 日本癌学会総会記事 72回 219 -219 2013年10月 [査読無し][通常論文]
  • 浜田俊幸, 石川正純, SUTHERLAND K, 宮本直樹, 白土博樹, 本間さと, 本間研一 日本生理学雑誌 75 (4) 206 -207 2013年07月01日 [査読無し][通常論文]
  • M. Ishikawa, H. Kojima, H. Tachibana, S. Tanabe, R. Suzuki, T. Minemura, N. Tohyama, Y. Narita, T. Nishio, S. Ishikura Medical Physics 40 (6) 246 2013年06月 [査読無し][通常論文]
     
    Purpose: In high‐accuracy radiation therapy such as intensity‐modulated radiotherapy (IMRT), dosimetric quality assurance is required to ensure the accuracy of the dose delivery. Although film dosimetry, associated with absolute dose measurement, is often used for this purpose, the uncertainty of film dosimetry is strongly influenced by the stability of the scanning device. This paper proposes a practical correction method for compensating scanner instability when making dose response curves. Methods: Gafchromic EBT3 films were irradiated with 6 MV X‐rays to 0, 10, 50, 100, 200 and 300 cGy. All films were scanned 1,000 times for 45 hours with about 2.7 minutes interval by a flat‐bed type image scanner (ES‐10000G, Seiko Epson Corp.). Pixel values for 1,000 images were automatically measured using a macro function of Image J (National Institutes of Health) to analyze the same area for each ROI, stored as the average of 50 x 50 pixel values. The stability of film measurement was assessed by analyzing optical density (OD) and corrected optical density, calculated by summing the OD of unirradiated film and net optical density (ODnet). Results: OD changes were significantly corrected, including post‐exposure density growth, compared to the original OD changes. This means that highly accurate film dosimetry, independent of the condition of the scanner device, may be possible by correcting OD with ODnet. Conclusion: In making dose response curves, dose uncertainty due to scanner device instability can be minimized by correcting OD values using the ODnet value. By using the presented method, a reduction of uncertainty in film dosimetry can be achieved. Furthermore, the procedure is simple and practical for clinical implementation. This research was supported by a grant for Clinical Cancer Research (10103757) from Ministry of Health, Labour and Welfare, Japan. © 2013, American Association of Physicists in Medicine. All rights reserved.
  • M. Ishikawa, S. Tanabe, S. Yamaguchi, N. Ukon, T. Yamanaka, K. Sutherland, N. Miyamoto, R. Suzuki, N. Katoh, K. Yasuda, H. Shirato Medical Physics 40 (6) 162 2013年06月 [査読無し][通常論文]
     
    Purpose: Molecular imaging is one of the important modalities in delineating tumors particularly in radiotherapy treatment planning. If the real‐time tumor position can be detected using molecular imaging during radiotherapy, it may be helpful for gated irradiation. A feasibility study on a beam gating system for radiotherapy using real‐time molecular imaging was conducted by the prototype and simulating a parallel plane PET system. Methods: Assuming that the motion of the positron source is constrained to the central plane, the source position can be calculated from a cross point of the Line of Response (LOR) and the central plane between detector surfaces. If a positron source is located at the ISO center, distribution of the cross points might be blurred due to random/scattered coincidence. Center Located Ratio (CLR) was defined as a ratio of LORs passing through the ISO center divided by the entire LORs. When dislocation for perpendicular direction is occurred, a distribution of cross points will be spread out and associated decrease of CLR value will be expected. Results: The behavior between real measurement and simulation was similar on proto‐type experiments, however, the Result from simulation for demonstrator might be different from actual measurement. RTRT system recognizes the position of a gold marker in the rate of 30 fps using two X‐ray television systems. It is shown that 15,000 events per second will be needed for an appropriate gating irradiation to recognize discrepancy over 2mm of time resolution in the parallel plane PET system demonstrator. Conclusion: A feasibility study was carried out to verify the potential for gating irradiation of tumors with real‐time molecular imaging using a parallel plane PET system. For an parallel plane PET system demonstrator, the possibility of detecting the tumor position with an accuracy of 2 mm from the ISO center with 500 events. This research was a part of the “Innovation COE Program for Future Drug Discovery and Medical Care” project and partially supported by the Grant‐in‐Aid for Project for Developing Innovation Systems of the Japanese Ministry of Education, Culture, Sports, Science and Technology. © 2013, American Association of Physicists in Medicine. All rights reserved.
  • 河合 理城, 出町 和之, 石川 正純, 白土 博樹, 上坂 充 電子情報通信学会総合大会講演論文集 2013 (1) 74 -74 2013年03月05日 [査読無し][通常論文]
  • 石川 正純 最新医学 68 (1) 131 -136 2013年01月 [査読無し][通常論文]
  • N. Miyamoto, M. Ishikawa, K. Sutherland, R. Suzuki, T. Matsuura, S. Takao, C. Toramatsu, H. Nihongi, S. Shimizu, R. Onimaru, K. Umegaki, H. Shirato Medical Physics 39 (6) 3661 -3662 2012年06月 [査読無し][通常論文]
     
    Purpose: In the real‐time tumor‐tracking radiotherapy system, fiducial markers are detected by X‐ray fluoroscopy. The fluoroscopic parameters should be optimized as low as possible in order to reduce unnecessary imaging dose. However, the fiducial markers could not be recognized due to effect of statistical noise in low dose imaging. Image processing is envisioned to be a solution to improve image quality and to maintain tracking accuracy. In this study, a recursive image filter adapted to target motion is proposed. Methods: A fluoroscopy system was used for the experiment. A spherical gold marker was used as a fiducial marker. About 450 fluoroscopic images of the marker were recorded. In order to mimic respiratory motion of the marker, the images were shifted sequentially. The tube voltage, current and exposure duration were fixed at 65 kV, 50 mA and 2.5 msec as low dose imaging condition, respectively. The tube current was 100 mA as high dose imaging. A pattern recognition score (PRS) ranging from 0 to 100 and image registration error were investigated by performing template pattern matching to each sequential image. The results with and without image processing were compared. Results: In low dose imaging, theimage registration error and the PRS without the image processing were 2.15±1.21 pixel and 46.67±6.40, respectively. Those with the image processing were 1.48±0.82 pixel and 67.80±4.51, respectively. There was nosignificant difference in the image registration error and the PRS between the results of low dose imaging with the image processing and that of high dose imaging without the image processing. Conclusions: The results showed that the recursive filter was effective in order to maintain marker tracking stability and accuracy in low dose fluoroscopy. © 2012, American Association of Physicists in Medicine. All rights reserved.
  • Naoki Miyamoto, Kenneth Sutherland, Ryusuke Suzuki, Taeko Matsuura, Chie Toramatsu, Seishin Takao, Hideaki Nihongi, Rumiko Kinoshita, Shinichi Shimizu, Rikiya Onimaru, Kikuo Umegaki, Hiroki Shirato, Masayori Ishikawa Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8316 83160 2012年05月01日 [査読無し][通常論文]
     
    In the real-time tumor-tracking radiotherapy (RTRT) system, the fiducial markers are inserted in or near the target tumor in order monitor the respiratory-induced motion of tumors. During radiation treatment, the markers are detected by continuous fluoroscopy operated at 30 frames/sec. The marker position is determined by means of a template pattern matching technique which is based on the normalized cross correlation. With high tube voltage, large current and long exposure, the fiducial marker will be recognized accurately, however, the radiation dose due to X-ray fluoroscopy increases. On the other hand, by decreasing the fluoroscopy parameter settings, the fiducial marker could be lost because the effect of statistical noise is increased. In the respiratory-gated radiotherapy, the error of the image guidance will induce the reduction of the irradiation efficiency and accuracy. In order to track the marker stably and accurately in low dose fluoroscopy, we propose the application of a recursive filter. The effectiveness of the image processing is investigated by tracking the static marker and the dynamic marker. The results suggest that the stability and the accuracy of the marker tracking can be improved by applying the recursive image filter in low dose imaging. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
  • 辻真太朗, 鈴木隆介, 安田耕一, 藤田勝久, 宮崎智夫, 石川正純, 白土博樹 日本放射線技術学会総会学術大会予稿集 68th 134 -134 2012年02月29日 [査読無し][通常論文]
  • 加藤徳雄, 鈴木隆介, 井上哲也, 安田耕一, 鬼丸力也, 清水伸一, 木村理奈, 石川正純, 白土博樹 日本医学放射線学会総会抄録集 71st S316 -S316 2012年02月29日 [査読無し][通常論文]
  • 石川正純 日本医学放射線学会総会抄録集 71st S86 2012年02月29日 [査読無し][通常論文]
  • 河合 理城, 出町 和之, 石川 正純, 白土 博樹, 上坂 充 年次大会 2012 (0) _J241034 -1-_J241034-3 2012年 [査読無し][通常論文]
     
    Currently, the area targeted by radiation therapy is wider than an actual tumor as the tumor moves during treatments Especially for a lung tumor, the radiation exposure to normal tissues is increased, as it tends to move more than other types of tumors One of the methods to reduce the exposure of normal tissues is RTRT (Real-time Tumor-tracking Radiation Therapy) In this research, we have attempted to predict the tumor motion using a prediction method called MSSA (Multi-channel Singular Spectrum Analysis) in the therapy This method reconstructs the time-series data with principal components and predicts the future data using the reconstructed data We predicted real tumor motions which were taken at Hokkaido University Hospital As a result, the errors between the predicted data and the raw data are about 1mm Also, we have developped the safety system with prediction This system is needed to stop the irradiation in case that the patient tumor moves dramatically such as cough or sneeze during a radiation therapy The result shows that the safety system can detect the unusual signal before a large movement
  • 右近直之, 棚邊哲史, 棚邊哲史, 山中琢, 山口哲, SUTHERLAND Kenneth, 鈴木隆介, 宮本直樹, 白土博樹, 石川正純 医学物理 Supplement 32 (3) 2012年
  • 石川正純 陽子線高線量率ラインスキャニングの革新的技術の研究 平成23年度 総括研究報告書 22-24 2012年 [査読無し][通常論文]
  • 石川正純 陽子線高線量率ラインスキャニングの革新的技術の研究 平成21−23年度 総合研究報告書 36-40 2012年 [査読無し][通常論文]
  • 原田慶一, 井上哲也, 安田耕一, 加藤徳雄, 清水伸一, 白土博樹, BENGUA Gerard, 石川正純, 中積宏之, 結城敏志, 小松嘉人 北海道外科雑誌 56 (2) 176-177 -177 2011年12月20日 [査読無し][通常論文]
  • 古坂 道弘, 鬼柳 善明, 住吉 孝, 白土 博樹, 石川 正純, 鈴木 隆介 工学教育研究講演会講演論文集 23 (59) 356 -357 2011年08月22日 [査読無し][通常論文]
  • T. Minemura, Y. Narita, M. Tamura, M. Ishikawa, S. Ozawa, T. Miyagishi, T. Nishio Medical Physics 38 (6) 3548 2011年06月 [査読無し][通常論文]
     
    Purpose: Recently, radiotherapy for cancer advances to the highly precise treatment by various technical progresses. The highly precise radiotherapy that seems to be intensity modulation radiation therapy (IMRT) popularizes rapidly now. Therefore high technology of radiotherapy is demanded, and the quality control / quality assurance (QC / QA) is needed. In this study, it is a purpose to make the third‐party evaluation program to perform the radiotherapy that is safe from IMRT. Methods: The measurement was executed with an anthropomorphic IMRT phantom by the on‐site visit. The IMRT phantom was divided into a phantom shell and a module. The IMRT treatment plan was drafted by each institution to satisfy the following optimization conditions. (1) The D95 prescription (PTV) was 2Gy. (2) The PTV maximum dose was considered to be less than 110 %. (3) Organ at risk (OAR) was considered to be less than 60 %. The dose inspection for a drafted IMRT treatment plan was executed with the ionization‐chamber dosimetry module and the film dosimetry module. Results: The evaluation of the absorbed dose was executed for two points in PTV. In addition, the dose distribution measured axial, coronal, and sagittal side with a film. For these measurement sides, the evaluation of the position gap was achieved in the part that the dose gradient became precipitous. For the ionization‐chamber dosimeter, the differences at two points in PTV were less than ±3 %. For the dose distribution with the films, the differences for the position gap were less than ±2 mm. Conclusions: In this study, it was developed the phantom for inspection and measurement machinery to assure of the quality for IMRT, and the third‐party evaluation program was made. In the future, it will be necessary to repeat inspection in plural institutions to raise the reliability of the inspection result. © 2011, American Association of Physicists in Medicine. All rights reserved.
  • 石川 正純 文芸春秋 89 (6) 206 -213 2011年06月 [査読無し][通常論文]
  • 石川 正純, 岡本 浩一 文芸春秋 89 (5) 202 -209 2011年05月 [査読無し][通常論文]
  • 石川正純 日本医学放射線学会総会抄録集 70th S73 2011年02月28日 [査読無し][通常論文]
  • 石川正純 日本放射線技術学会総会学術大会予稿集 67th 66 2011年02月25日 [査読無し][通常論文]
  • 高尾聖心, 但野茂, BENGUA Gerard, 石川正純, 白土博樹 バイオエンジニアリング講演会講演論文集 23rd (23) 443-444 -444 2011年01月07日 [査読無し][通常論文]
  • 高尾 聖心, 但野 茂, BENGUA Gerard, 石川 正純, 白土 博樹 バイオエンジニアリング講演会講演論文集 2010 (0) 443 -444 2011年 [査読無し][通常論文]
  • 高尾聖心, 但野茂, 田口大志, 安田耕一, 鬼丸力也, 石川正純, 鈴木隆介, GERARD Bengua, 白土博樹 日本生体医工学会大会プログラム・論文集(CD−ROM) 50th ROMBUNNO.O1-9-5 2011年 [査読無し][通常論文]
  • 石川正純 陽子線高線量率ラインスキャニングの革新的技術の研究 平成22年度 総括・分担研究報告書 16 30-33 -123 2011年 [査読無し][通常論文]
  • 石川正純 がん医療の均てん化に資する放射線治療の推進及び品質管理に係る研究 平成22年度 総括・分担研究報告書 152-153 2011年 [査読無し][通常論文]
  • 石川正純 高精度治療技術による低リスク高線量放射線治療に関する臨床研究 平成22年度 総括研究報告書 23-25 2011年 [査読無し][通常論文]
  • 江口 菜弥帆, 石川 正純, 作原 祐介, 阿保 大介, 太田 真緒, Sutherland Kenneth, 白土 博樹 放射線防護分科会会誌 0 (31) 33 -33 2010年10月14日 [査読無し][通常論文]
  • 安田耕一, 長谷川雅一, 鬼丸力也, 木下留美子, 加藤徳雄, 田口大志, 清水伸一, 井上哲也, 小野寺俊輔, 溝口史樹, 青山英史, 白土博樹, 志賀哲, 岡本祥三, 玉木長良, 石川正純, SUTHERLAND Kenneth, BENGUA Gerard, 宮本直樹, 鈴木隆介 Jpn J Radiol 28 (Supplement 1) 14 -14 2010年07月25日 [査読無し][通常論文]
  • 長谷川雅一, 安田耕一, 吉田大介, 加藤徳雄, 鬼丸力也, 浅野剛, 白土博樹, 本間明宏, 折舘伸彦, 福田諭, 石川正純, BENGUA Gerard, SUTHERLAND Kenneth, 宮本直樹, 鈴木隆介 Jpn J Radiol 28 (Supplement 1) 7 -7 2010年07月25日 [査読無し][通常論文]
  • 関原和正, 石川正純, SUTHERLAND Kenneth, BENGUA Gerard, 宮本直樹, 鈴木隆介, 清水伸一, 白土博樹 Jpn J Radiol 28 (Supplement 1) 15 -15 2010年07月25日 [査読無し][通常論文]
  • 石川正純, 江口菜弥帆, 作原大介, 阿保大介, 太田真緒, SUTHERLAND Kenneth, BENGUA Gerard, 鈴木隆介, 宮本直樹, 白土博樹 日本医学放射線学会総会抄録集 69th S378 -S378 2010年02月28日 [査読無し][通常論文]
  • 井上哲也, 加藤徳雄, 青山英史, 鬼丸力也, 石川正純, 田口大志, 白土博樹 日本医学放射線学会総会抄録集 69th S193-S194 -S194 2010年02月28日 [査読無し][通常論文]
  • 江口菜弥帆, 石川正純, 作原祐介, 阿保大介, 太田真緒, KENNETH Sutherland, 白土博樹 日本放射線技術学会総会学術大会予稿集 66th 153-154 -154 2010年02月26日 [査読無し][通常論文]
  • M. Ishikawa, S. Yamaguchi, S. Tanabe, G. Bengua, K. Sutherland, R. Suzuki, N. Miyamoto, K. Nishijima, N. Katoh, H. Shirato INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 78 (3) S674 -S674 2010年 [査読無し][通常論文]
  • N. Miyamoto, M. Ishikawa, G. Bengua, K. Sutherland, R. Suzuki, H. Shirato INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 78 (3) S678 -S678 2010年 [査読無し][通常論文]
  • S. Tanabe, M. Ishikawa, S. Yamaguchi, G. Bengua, K. Sutherland, R. Suzuki, N. Miyamoto, N. Katoh, R. Onimaru, H. Shirato INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 78 (3) S749 -S749 2010年 [査読無し][通常論文]
  • 石川正純 高精度治療技術による低リスク高線量放射線治療に関する臨床研究 平成21年度 総括研究報告書 12 2010年 [査読無し][通常論文]
  • 石川正純 がん医療の均てん化に資するがん診療連携拠点病院の機能強化に関する研究 平成21年度 総括・分担研究報告書 34-35 2010年 [査読無し][通常論文]
  • 白土博樹, 青山英史, 石川正純, 清水伸一, 鬼丸力也, 溝脇尚志 日本癌治療学会誌 44 (2) 256 -256 2009年09月14日 [査読無し][通常論文]
  • 宮本直樹, SUTHERLAND Kenneth, 石川正純, 鈴木隆介, BENGUA Gerard, 木村傑, 清水伸一, 青山英史, 鬼丸力也, 白土博樹 医学物理 Supplement 29 (3) 150-151 2009年09月 [査読無し][通常論文]
  • 山口哲, 石川正純, 棚邊哲史, BENGUA Gerard, SUTHERLAND Kenneth, 青山英史, 武島嗣英, 白土博樹 医学物理 Supplement 29 (3) 174-175 2009年09月 [査読無し][通常論文]
  • 木村傑, 宮本直樹, 石川正純, SUTHERLAND Kenneth, BENGUA Gerard, 鈴木隆介, 清水伸一, 青山英史, 鬼丸力也, 白土博樹 医学物理 Supplement 29 (3) 148-149 2009年09月 [査読無し][通常論文]
  • 石川正純 日本放射線腫よう学会誌 21 (Supplement 1) 106 2009年08月19日 [査読無し][通常論文]
  • 石川正純, サザランド ケネス, ベングア ジェラード, 鈴木隆介, 宮本直樹, 加藤徳雄, 清水伸一, 鬼丸力也, 青山英史, 白土博樹 日本放射線腫よう学会誌 21 (Supplement 1) 158 2009年08月19日 [査読無し][通常論文]
  • 井上哲也, 加藤徳雄, 青山英史, 鬼丸力也, 石川正純, 田口大志, 白土博樹 日本放射線腫よう学会誌 21 (Supplement 1) 159 2009年08月19日 [査読無し][通常論文]
  • 白土博樹, 青山英史, 鬼丸力也, 清水伸一, 石川正純, 西岡健 治療学 43 (7) 781-783 -783 2009年07月10日 [査読無し][通常論文]
  • M. Komeda, H. Kumada, M. Ishikawa, T. Nakamura, K. Yamamoto, A. Matsumura APPLIED RADIATION AND ISOTOPES 67 (7-8) S254 -S257 2009年07月 [査読無し][通常論文]
     
    The thermal neutron flux can be easily measured in real time by using the scintillator with optical fiber (SOF) detector. However the irradiation damage under high-intensity neutron flux causes deterioration of the SOF detector due to radiation damage to the plastic scintillator in which (6)LiF is blended. After irradiating the SOF detector for 4 h (thermal neutron fluence is approximately 2.0 x 10(13) neutrons/cm(2)), the sensitivity of the SOF detector decreased by 3.0%. After irradiating the SOF detector for 2 months (thermal neutron fluence approximately 6.4 x 10(14) neutrons/cm(2)), the sensitivity was reduced to 42% of baseline. Supposing that the thermal neutron fluence is 2 x 10(12) neutrons/cm(2) on the surface of a patient in a BNCT treatment, the sensitivity of the SOF detector is reduced by approximately 0.3%. This report presents investigations on the deterioration of the SOF detector in irradiation experiments. (C) 2009 Elsevier Ltd. All rights reserved.
  • 出町和之, ZHU Haitao, 石川正純, 白土博樹 日本AEM学会誌 17 (2) 222-226 -226 2009年06月10日 [査読無し][通常論文]
     
    In this research, the Singular Spectrum Analysis (SSA) was applied for the prediction of time-series data. The prediction calculation were performed for the time-series data of the atmosphere temperature, the rank of star shining, and the displacement of a tumor in human lang. The prediction results showed good agreement with the measured data, then the validity of this method was verified. It can be said that this method is hopeful for the realization of the chasing radiotherapy.
  • 出町 和之, 朱 海涛, 石川 正純, 白土 博樹 日本AEM学会誌 17 (2) 222 -226 2009年06月10日 [査読無し][通常論文]
     
    In this research, the Singular Spectrum Analysis (SSA) was applied for the prediction of time-series data. The prediction calculation were performed for the time-series data of the atmosphere temperature, the rank of star shining, and the displacement of a tumor in human lang. The prediction results showed good agreement with the measured data, then the validity of this method was verified. It can be said that this method is hopeful for the realization of the chasing radiotherapy.
  • 遠藤暁, 高田真志, 田中浩基, 鬼塚昌彦, 田中憲一, 宮原信幸, 星正治, 石川正純, 木村真三, 靜間清 NIRS−M (Natl Inst Radiol Sci) (226) 232-233 2009年06月 [査読無し][通常論文]
  • M. Ishikawa, G. Bengua, K. L. Sutherland, J. Hiratsuka, N. Katoh, S. Shimizu, H. Aoyama, K. Fujita, R. Yamazaki, K. Horita, H. Shirato PHYSICS IN MEDICINE AND BIOLOGY 54 (7) 2079 -2092 2009年04月 [査読無し][通常論文]
     
    The purpose of this study was to develop a novel scintillation dosimeter for in vivo dosimetry in Ir-192 brachytherapy via the pulse-counting mode. The new dosimeter was made from a plastic scintillator shaped into a hemisphere of diameter 1 mm and connected to the tip of a plastic optical fiber. The relationship between pulse counts and absorbed dose was derived based on the assumption that scintillation photons from the incident gamma ray are proportional to the absorbed dose. An equation for the conversion of pulse counts to water-equivalent dose was deduced wherein the pulse height spectrum from scintillation photons was assumed to be exponential. To confirm its accuracy, the dose rate distribution in a water phantom was measured by the present dosimeter and this was compared with Monte Carlo simulations, resulting in a discrepancy of less than 1.97%. It was found that the dosimeter has a wide dynamic range of linearity up to an order of magnitude of almost 10(3), including corrections for loss of counts due to pile-up.
  • 石川正純, SUTHERLAND Kenneth, 宮本直樹, BENGUA Gerard, 清水伸一, 青山英史, 鬼丸力也, 木村傑, 白土博樹 医学物理 Supplement 29 (2) 194-195 2009年04月 [査読無し][通常論文]
  • 木村傑, 石川正純, SUTHERLAND Kenneth, 宮本直樹, BENGUA Gerard, 鈴木隆介, 清水伸一, 青山英史, 鬼丸力也, 白土博樹 医学物理 Supplement 29 (2) 196-197 2009年04月 [査読無し][通常論文]
  • 宮本直樹, SUTHERLAND Kenneth, 石川正純, 鈴木隆介, BENGUA Gerard, 木村傑, 清水伸一, 青山英史, 鬼丸力也, 白土博樹 医学物理 Supplement 29 (2) 192-193 2009年04月 [査読無し][通常論文]
  • 原裕, 島崎紘亘, 金子純一, 高田英治, 藤田文行, 久保直樹, 石川正純, 古坂道弘, 白土博樹 医学物理 Supplement 29 (2) 190-191 2009年04月 [査読無し][通常論文]
  • 棚邊哲史, 石川正純, 山口哲, 武島嗣英, 鈴木隆介, 宮本直樹, 加藤徳雄, 清水伸一, 鬼丸力也, 白土博樹 医学物理 Supplement 29 (2) 101-102 2009年04月 [査読無し][通常論文]
  • 遠藤暁, 高田真志, 田中浩基, 鬼塚昌彦, 田中憲一, 宮原信幸, 星正治, 石川正純, 木村真三, 靜間清 医学物理 Supplement 29 (2) 133-134 2009年04月 [査読無し][通常論文]
  • 山口哲, 石川正純, 棚邊哲史, BENGUA Gerard, SUTHERLAND Kenneth, 青山英史, 武島嗣英, 白土博樹 NIRS−R (Natl Inst Radiol Sci) (60) 137-138 2009年03月 [査読無し][通常論文]
  • 安田耕一, 白土博樹, 岡本祥三, 志賀哲, SUTHERLAND Ken, 加藤徳雄, 長谷川雅一, 鬼丸力也, BENGUA Gerard, 石川正純 日本医学放射線学会総会抄録集 68th S267 -S267 2009年02月28日 [査読無し][通常論文]
  • 加藤徳雄, 志賀哲, 長谷川雅一, 鬼丸力也, 安田耕一, 清水伸一, ベングア ジェラード, 石川正純, 玉木長良, 白土博樹 日本医学放射線学会総会抄録集 68th S307-S308 -S308 2009年02月28日 [査読無し][通常論文]
  • 高森清華, 堀田賢治, 斎藤英一, 山崎理衣, 藤田勝久, SUTHERLAND Kenneth, 石川正純 日本放射線技術学会総会学術大会予稿集 65th 242 2009年02月27日 [査読無し][通常論文]
  • K. Sutherland, M. Ishikawa, G. Bengua, H. Shirato INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 75 (3) S600 -S600 2009年 [査読無し][通常論文]
  • 遠藤暁, 高田真志, 田中浩基, 鬼塚昌彦, 田中憲一, 宮原信幸, 星正治, 石川正純, 木村真三, 靜間清 日本原子力学会中国・四国支部研究発表会要旨集 3rd 38-41 2009年 [査読無し][通常論文]
  • 白土博樹, 鬼丸力也, BENGUA Gerard, 石川正純, 井上哲也, 清水伸一, 木下留美子, 青山英史 定位放射線治療による予後改善に関する研究 平成20年度 総括研究報告書 12-13 2009年 [査読無し][通常論文]
  • 石川正純 高精度治療技術による低リスク高線量放射線治療に関する臨床研究 平成20年度 総括研究報告書 20-21 2009年 [査読無し][通常論文]
  • 石川正純 日本原子力研究開発機構JAEA−Review 437-444 2009年01月 [査読無し][通常論文]
  • 山口哲, 石川正純, 棚邊哲史, GERARD Bengua, KENNETH Sutherland, 青山英史, 武島嗣英, 白土博樹 日本放射線腫よう学会誌 20 (Supplement 1) 267 2008年09月22日 [査読無し][通常論文]
  • 棚邊哲史, 石川正純, 山口哲, 武島嗣英, GERARD Bengua, KENNETH Sutherland, 加藤徳雄, 清水伸一, 鬼丸力也, 白土博樹 日本放射線腫よう学会誌 20 (Supplement 1) 268 2008年09月22日 [査読無し][通常論文]
  • KENNETH Sutherland, 石川正純, GERARD Bengua, 鬼丸力也, 清水伸一, 青山英史, 藤田勝久, 山崎里依, 白土博樹 日本放射線腫よう学会誌 20 (Supplement 1) 264 2008年09月22日 [査読無し][通常論文]
  • 石川正純, 平塚純一, 長瀬尚巳, GERARD Bengua, KENNETH Sutherland, 加藤徳雄, 清水伸一, 鬼丸力也, 青山英史, 白土博樹 日本放射線腫よう学会誌 20 (Supplement 1) 251 2008年09月22日 [査読無し][通常論文]
  • 石川正純 日本放射線腫よう学会誌 20 (Supplement 1) 90 2008年09月22日 [査読無し][通常論文]
  • M. Hoshi, S. Endo, K. Tanaka, M. Ishikawa, T. Straume, K. Komura, W. Ruehm, E. Nolte, T. Huber, Y. Nagashima, R. Seki, K. Sasa, K. Sueki, H. Fukushima, S. D. Egbert, T. Imanaka RADIATION AND ENVIRONMENTAL BIOPHYSICS 47 (3) 313 -322 2008年07月 [査読無し][通常論文]
     
    In the process of developing a new dosimetry system for atomic bomb survivors in Hiroshima and Nagasaki (DS02), an intercomparison study between (152)Eu and (36)Cl measurements was proposed, to reconcile the discrepancy previously observed in the Hiroshima data between measurements and calculations of thermal neutron activation products. Nine granite samples, exposed to the atomic-bomb radiation in Hiroshima within 1,200 m of the hypocenter, as well as mixed standard solutions containing known amounts of europium and chlorine that were neutron-activated by a (252)Cf source, were used for the intercomparison. Gamma-ray spectrometry for (152)Eu was carried out with ultra low-background Ge detectors at the Ogoya Underground Laboratory, Kanazawa University, while three laboratories participated in the (36)Cl measurement using accelerator mass spectrometry (AMS): The Technical University of Munich, Germany, the Lawrence Livermore National Laboratory, USA and the University of Tsukuba, Japan. Measured values for the mixed standard solutions showed good agreement among the participant laboratories. They also agreed well with activation calculations, using the neutron fluences monitored during the (252)Cf irradiation, and the corresponding activation cross-sections taken from the JENDL-3.3 library. The measured-to-calculated ratios obtained were 1.02 for (152)Eu and 0.91-1.02 for (36)Cl, respectively. Similarly, the results of the granite intercomparison indicated good agreement with the DS02 calculation for these samples. An average measured-to-calculated ratio of 0.98 was obtained for all granite intercomparison measurements. The so-called neutron discrepancy that was previously observed and that which included increasing measured-to-calculated ratios for thermal neutron activation products for increasing distances beyond 1,000 m from the hypocenter was not seen in the results of the intercomparison study. The previously claimed discrepancy could be explained by insufficient understanding of the measured data.
  • 石川 正純, 平塚 純一, 長瀬 尚巳, 大坂 康博, BENGUA Gerard, 白土 博樹 医学物理 : 日本医学物理学会機関誌 = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 28 285 -286 2008年04月01日
  • 山口 哲, 石川 正純, 棚辺 哲史, BENGUA Gerard, SUTHERLAND Kenneth, 青山 英史, 武島 嗣英, 白土 博樹 医学物理 : 日本医学物理学会機関誌 = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 28 256 -257 2008年04月01日 [査読無し][通常論文]
  • 原 裕, 金子 純一, 高田 英治, 藤田 文行, 久保 直樹, 石川 正純, 古坂 道弘, 白土 博樹 医学物理 : 日本医学物理学会機関誌 = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 28 (0) 283 -284 2008年04月01日 [査読無し][通常論文]
  • 白土博樹, 鬼丸力也, 石川正純, 田口大志, 加藤徳雄, 清水伸一 MOOK肺癌の臨床 2008-2009 319-326 2008年03月31日 [査読無し][通常論文]
  • 石川正純 日本医学放射線学会総会抄録集 67th S94 2008年02月28日 [査読無し][通常論文]
  • G. R. Borst, H. Shirato, J. Nijkamp, R. Onimaru, M. Ishikawa, J. V. Lebesque, J. Sonke INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 72 (1) S68 -S69 2008年 [査読無し][通常論文]
  • 原裕, 金子純一, 高田英治, 藤田文行, 久保直樹, 石川正純, 古坂道弘, 白土博樹 日本原子力学会北海道支部研究発表会講演要旨集 26th 4-5 2008年 [査読無し][通常論文]
  • 白土博樹, 鬼丸力也, 田口大志, 加藤徳雄, 石川正純 定位放射線治療による予後改善に関する研究 平成19年度 総括研究報告書 9-10 2008年 [査読無し][通常論文]
  • S. Endo, K. Shizuma, K. Tanaka, M. Ishikawa, W. Ruehm, S. D. Egbert, M. Hoshi HEALTH PHYSICS 93 (6) 689 -695 2007年12月 [査読無し][通常論文]
     
    For about one decade, activation measurements performed on environmental samples from a distance larger than 1 km from the hypocenter of the atomic-bomb explosion over Hiroshima suggested much higher thermal neutron fluences to the survivors than predicted. This caused concern among the radiation protection community and prompted a complete re-evaluation of all aspects of survivor dosimetry. While it was shown recently that secondary neutrons from cosmic radiation and other sources have probably been the reason for the high measured concentrations of the long-lived radioisotope Cl-36 in these samples, the source for high measured concentrations of the short-lived radionuclides Eu-152 and Co-60 has not yet been investigated in detail. In order to quantify the production of Eu-152 and Co-60 in environmental samples by secondary neutrons from cosmic radiation, thermal neutron fluxes were measured by means of a He-3 gas proportional counter in various buildings where these samples had been and still are being stored. Because a Cf-252 neutron source has been operated occasionally close to one of the sample storage rooms, additional neutron flux measurements were carried out when the neutron source was in operation. The thermal neutron fluxes measured ranged from 0.00017 to 0.00093 n cm(-2) s(-1) and depended on the floor number of the investigated building. Based on the measured neutron fluxes, the specific activities from the reactions Eu-151(n,y)Eu-152 and Co-59(n,gamma)Co-60 in the atomic-bomb samples were estimated to be 7.9 mBq g(-1) Eu and 0.27 mBq g(-1) Co, respectively, in saturation. These activities are much lower than those recently measured in samples that had been exposed to atomic-bomb neutrons. It is therefore concluded that environmental and moderated Cf-252. neutrons are not the source for the high activities that had been measured in these samples.
  • 熊田博明, 米田政夫, 中村剛実, 山本和喜, 楠剛, 石川正純, 中川義信 日本原子力学会秋の大会予稿集(CD−ROM) 2007 F12 2007年09月07日 [査読無し][通常論文]
  • Satoru Endo, Masashi Takada, Yoshihiko Onizuka, Kenichi Tanaka, Naoko Maeda, Masayori Ishikawa, Nobuyuki Miyahara, Naofumi Hayabuchi, Kiyoshi Shizuma, Masaharu Hoshi JOURNAL OF RADIATION RESEARCH 48 (5) 397 -406 2007年09月 [査読無し][通常論文]
     
    Microdosimetric single event spectra as a function of depth in a phantom for the 290 MeV/nucleon therapeutic carbon beam at HIMAC were measured by using a tissue equivalent proportional counter (TEPC). Two types of geometries were used: one is a fragment particle identification measurement (PID-mode) with time of flight (TOF) method without a backward phantom, and the other is an in-phantom measurement (IPM-mode) with a backward phantom. On the PID-mode geometry, fragments produced by carbon beam in a phantom are identified by the AE-TOF distribution between two scintillation counters positioned up- and down-stream relative to the tissue equivalent proportional counter (TEPC). Lineal energy distributions for carbon and five ion fragments (proton, helium, lithium, beryllium and boron) were obtained in the lineal-energy range of 0.1-1000 keV/gm at eight depths (7.9-147.9 mm) in an acrylic phantom. In the IPM-mode geometry, the total lineal energy distributions measured at eight depths (61.9-322.9 mm) were compared with the distributions in the PID-mode. Both spectra are consistent with each other. This shows that the PID-mode measurement can be discussed as the equivalent of the phantom measurement. The dose distribution of the carbon beam and fragments were obtained separately. In the depth dose curve, the Bragg peak was observed. Relative biological effectiveness (RBE) for the carbon beam in the acrylic phantom was obtained based on a biological response function as a lineal-energy. The RBE of carbon beam had a maximum of 4.5 at the Bragg peak. Downstream of the Bragg peak, the RBE rapidly decreases. The RBE of fragments is dominated by Boron particles around the Bragg peak region.
  • 石川正純, 鈴木恵士朗, 木下留美子, 藤田勝久, 山崎理衣, 笈田将皇, 白土博樹 頭けい部癌 33 (2) 64 2007年05月15日 [査読無し][通常論文]
  • Hiromitsu Watanabe, Naoki Kashimoto, Junko Kajimura, Masayori Ishikawa, Kenji Kamiya JOURNAL OF RADIATION RESEARCH 48 (3) 205 -210 2007年05月 [査読無し][通常論文]
     
    This study was undertaken to investigate induction of tumors by monoenergetic neutrons in B6C3F1 mice. Individual groups of 6 week-old animals of both sexes (about 30 mice/group) were exposed to 0.5 Gy of various monoenergetic neutrons (dose rate 0.5 cGy/min) and then observed for 13 months. The incidences of tumors (mainly liver neoplasms) in non-irradiated male and female controls were 11% and 0%, respectively. In the irradiated animals, the incidences were 53%, 50%, 60% and 43% in males, and 75%, 81%, 71%, and 85% in females, after 0.18, 0.32, 0.6 and 1.0 MeV neutron exposure, respectively. There were no significant differences in the tumor induction rate among the different energy groups.
  • M. Ishikawa, Y. Osaka, J. Hiratsuka, G. Bengua, H. Shirato INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 69 (3) S45 -S46 2007年 [査読無し][通常論文]
  • 笈田将皇, 石川正純, 藤野賢治, 加藤徳雄, 田口大志, 白土博樹, 渡辺良晴 日本放射線腫よう学会誌 18 (Supplement 1) 199 2006年10月25日 [査読無し][通常論文]
  • 石川正純, 笈田将皇, 加藤徳雄, 藤野賢治, 大坂康博, 白土博樹 日本放射線腫よう学会誌 18 (Supplement 1) 199 2006年10月25日 [査読無し][通常論文]
  • 鄭歩宏, 劉暁濱, 笈田将皇, 石川正純, 藤野賢治, 鬼丸力也, 白土博樹 日本放射線腫よう学会誌 18 (Supplement 1) 201 2006年10月25日 [査読無し][通常論文]
  • 笈田将皇, 石川正純, 藤田勝久, 渡辺良晴 日本放射線技術学会雑誌 62 (9) 1237 -1237 2006年09月20日 [査読無し][通常論文]
  • 笈田 将皇, 石川 正純, 藤田 勝久, 渡辺 良晴 日本放射線技術學會雜誌 62 (9) 1237 -1237 2006年09月20日 [査読無し][通常論文]
  • 中川恵一, 石川正純, 上坂充, 斉藤鉄夫 日本原子力学会誌 48 (6) 398 -402 2006年06月 [査読無し][通常論文]
  • 中川 恵一, 石川 正純, 上坂 充, 斉藤 鉄夫 日本原子力学会誌 = Journal of the Atomic Energy Society of Japan 48 (6) 398 -402 2006年06月 [査読無し][通常論文]
  • 遠藤暁, 鬼塚昌彦, 高田真志, 田中憲一, 星正治, 石川正純, 宮原信幸, 前田直子, 早淵尚文 NIRS−M (Natl Inst Radiol Sci) (192) 187-189 2006年05月 [査読無し][通常論文]
  • Reduction of prostate movement using orthogonal diagnostic x-rays of real-time tumor-tracking system and fiducial gold markers
    M.Oita, M Ishikawa, R Onimaru, Y Osaka, H Aoyama, K Suzuki, M Fujino, Y Watanabe, K Fujita, H Shirato, K Miyasaka Proceedings of 1st Hokkaido International Croscutting Symposium Molecular Bio-imaging and 4D Image-guided radiotherapy 65 -65 2006年 [査読無し][通常論文]
  • 遠藤暁, 田中憲一, 石川正純, 小村和久, 静間清, 星正治 広島および長崎における原子爆弾放射線被曝線量の再評価 線量評価システム2002 下巻 平成18年 736-740 2006年 [査読無し][通常論文]
  • 星正治, 遠藤暁, 田中憲一, 石川正純, STRAUME Tore, 小村和久, RUEHM Werner, NOLTE Eckehart, HUBER Thomas, 長島泰夫, 福嶋浩人, 今中哲二 広島および長崎における原子爆弾放射線被曝線量の再評価 線量評価システム2002 下巻 平成18年 590-599 2006年 [査読無し][通常論文]
  • 石川正純, 熊田博明, BENGUA Gerard, 町島祐一, 高橋浩之 UTNL−R(東京大学大学院工学系研究科附属原子力工学研究施設) (0449) 7-8 2006年 [査読無し][通常論文]
  • 石川 正純, 中沢 正治 Isotope news 0 (620) 16 -19 2005年12月01日 [査読無し][通常論文]
  • M Ishikawa, H Kumada, K Yamamoto, J Kaneko, G Bengua, H Unesaki, Y Sakurai, K Tanaka, T Kosako NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 551 (2-3) 448 -457 2005年10月 [査読無し][通常論文]
     
    A wide range thermal neutron detector was developed based on the Scintillator with Optical Fiber (SOF) detector which has been previously used for thermal neutron monitoring during boron neutron capture therapy irradiation. With this new detector system we intended to address the issues of real-time thermal neutron flux measurement and the simultaneous measurement of a wide range of thermal neutron flux in a BNCT irradiation field which were difficult to implement with the gold wire activation method. The dynamic range of linearity of the SOF detector was expanded by using a plastic scintillator with a rapid decay time. On the other hand, the contribution of gamma rays and fast neutrons in the measured signals were compensated from those obtained by a pair of SOF detectors, one with a (LiF)-Li-6 neutron converter and the other without. The discrimination level for the measured signals was also optimized to further reduce the contribution of gamma rays and fast neutrons signals. A non-paralyzable system model was applied to correct for the dead-time in the detector system. A good agreement between the thermal neutron flux measured by the gold wire activation method and the paired SOF detector system was observed. However, measurements which would normally take a few days to perform with the gold wire activation method were obtained in just about 15 min using the SOF detector system. We also confirmed the dynamic range of linearity for the SOF detector system to be in the order of magnitude of 10(4). (c) 2005 Elsevier B.V. All rights reserved.
  • 石川正純, 高橋浩之, 小野公二, 桜井良憲, 熊田博明, 町島祐一 放射線 31 (4) 279-285 -285 2005年10月 [査読無し][通常論文]
  • 冨田文雄, 雨宮邦招, 高橋浩之, 石川正純, 中沢正治 応用物理学会学術講演会講演予稿集 66th (1) 84 2005年09月07日 [査読無し][通常論文]
  • 石川 正純, 平澤 雅彦, 富谷 武浩, 村山 秀雄, 星 正治 医学物理 : 日本医学物理学会機関誌 = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 25 (1) 3 -12 2005年03月31日 [査読無し][通常論文]
     
    The kinematics of boron compounds in vivo is crucial to fully and safely utilize boron neutron capture therapy. In this paper, we proposed a prompt gamma-ray Compton scatter camera (PG-CSC), which can evaluate the 3-D kinematics of boron compounds without invasion. This PG-CSC combines a Compton camera with prompt gamma-ray analysis. The results of its design optimization and tests using simulations showed that one-hour-measurement was sufficient to evaluate a 3-D boron concentration distribution in a rat's brain with the resolution of 1mm in FWHM.
  • 石川正純, 平沢雅彦, 富谷武浩, 村山秀雄, 星正治 医学物理 25 (1) 3 -12 2005年03月31日 [査読無し][通常論文]
     
    The kinematics of boron compounds in vivo is crucial to fully and safely utilize boron neutron capture therapy. In this paper, we proposed a prompt gamma-ray Compton scatter camera (PG-CSC), which can evaluate the 3-D kinematics of boron compounds without invasion. This PG-CSC combines a Compton camera with prompt gamma-ray analysis. The results of its design optimization and tests using simulations showed that one-hour-measurement was sufficient to evaluate a 3-D boron concentration distribution in a rat's brain with the resolution of 1mm in FWHM.
  • 山口達, 白石和正, 金子純一, 片桐政樹, 石川正純, 沢村晃子 日本原子力学会春の年会要旨集 43rd 186 2005年03月11日 [査読無し][通常論文]
  • 星正治, 遠藤暁, 石川正純, 小村和久, 長島泰夫, 福嶋浩人, 今中哲二 KURRI KR (114) 42-48 2005年03月 [査読無し][通常論文]
  • 石川正純, 石丸伊知郎, 石井知彦, 井上祐介, 奥田貴啓, 藤井義樹 精密工学会大会学術講演会講演論文集 2005 B62 2005年03月01日 [査読無し][通常論文]
  • M Yamauchi, M Ishikawa, M Hoshi MEDICAL PHYSICS 32 (1) 85 -92 2005年01月 [査読無し][通常論文]
     
    Computational models of human anatomy, along with Monte Carlo radiation transport simulations, have been used by Snyder et al. [MIRD Pamphlet No. 5, revised (The Society of Nuclear Medicine, New York, 1978)], Cristy and Eckerman [ORNL/TM-8381/VI, Oak Ridge National Laboratory, Oak Ridge, TN (1987)] and Zubal et al. [Med. Phys. 21, 299-302 (1994)] to estimate internal organ doses from internal and external radiation sources. These were created using physiological data from Caucasoid subjects but not from other races. There is a need for research to determine whether the obvious differences from the Caucasoid anatomy make these models unsuitable for estimating the absorbed dose in other races such as the Mongoloid. We used the cranial region of the adult Japanese male to represent the Mongoloid race. This region contains organs that are highly sensitive to radiation. The cranial region of a physical phantom produced by KYOTO KAGAKU Co., LTD. using numerical data from a Japanese Reference Man [Tanaka, Nippon Acta. Radiol. 48, 509-513 (1988)] was used to supply the data for the geometry of a stylized computational model. Our computational model was constructed with equations rather than voxel-based, in order to deal with as small a number of parameters as possible in the computer simulation experiment. The accuracy of our computational model was checked by comparing simulated experimental results obtained with MCNP4C with actual doses measured with thermoluminescence dosimeters (TLDs) inside the physical phantom from which our computational model was constructed. The TLDs, whose margin of error is less than +/-10%, were arranged at six positions. Co-60 was used as the radiation source. The irradiated dose was 2 Gy in terms of air kerma. In the computer simulation experiments, we used our computational model and Cristy's computational model, whose component data are those of the tissue substitute materials and of the human body as published in ICRU Report 46. The observed absorbed dose values (Gy) at all six points were calculated as the percentage difference between MCNP4C simulation and the TLDs. In our computational model, the average values of all the percentage differences were 6.0 +/- 4.0% (tissue substitute materials) and 7.6 +/- 6.6% (ICRU Report 46), respectively. In Cristy's model, the corresponding values were 20.4 +/- 3.8% (tissue substitute materials) and 21.0 +/- 4.1% (ICRU Report 46), respectively. Considering the margin of error in the radiation sensitivity of the TLDs, this study validates our computational model as a test object for radiation dosimetry studies. (C) 2005 American Association of Physicists in Medicine.
  • 山口達, 白石和正, 金子純一, 片桐政樹, 石川正純, 沢村晃子 日本原子力学会春の年会要旨集 43rd 2005年
  • 石川正純, 高橋浩之, 熊田博明, 桜井良憲, 町島祐一 電気学会原子力研究会資料 NE-05 (6-10) 7-11 -11 2005年 [査読無し][通常論文]
  • 鬼塚昌彦, 遠藤暁, 田中憲一, 桜井良憲, 石川正純, 高田真志, 前田直子, 早淵尚文, 高辻俊宏 京都大学原子炉実験所学術講演会報文集 39th 97-100 2005年01月 [査読無し][通常論文]
  • M Ishikawa, K Ono, Y Sakurai, H Unesaki, A Uritani, G Bengua, T Kobayashi, K Tanaka, T Kosako APPLIED RADIATION AND ISOTOPES 61 (5) 775 -779 2004年11月 [査読無し][通常論文]
     
    A new thermal neutron monitor for boron neutron capture therapy was developed in this study. We called this monitor equipped boron-loaded plastic scintillator that uses optical fiber for signal transmission as an [scintillator with optical fiber] SOF detector. A water phantom experiment was performed to verify how the SOF detector compared with conventional method of measuring thermal neutron fluence. Measurements with a single SOF detector yielded indistinguishable signals for thermal neutrons and gamma rays. To account for the gamma ray contribution in the signal recorded by the SOF detector, a paired SOF detector system was employed. This was composed of an SOF detector with boron-loaded scintillator and an SOF detector with a boron-free scintillator. The difference between the recorded counts of these paired SOF detectors was used as the measure of the gamma ray contribution in the measured neutron fluence. The paired SOF detectors were ascertained to be effective in measuring thermal neutron flux in the range above 10(6) (n/cm(2)/s). Clinical trials using paired SOF to measure thermal neutron flux during therapy confirmed that paired SOF detectors were effective as a real-time thermal neutron flux monitor. (C) 2004 Elsevier Ltd. All rights reserved.
  • 足立 にれか, 石川 正純 保健物理 : hoken buturi 39 (3) 160 -164 2004年09月 [査読無し][通常論文]
  • 足立にれか, 石川正純 保健物理 39 (3) 160-164 -164 2004年09月 [査読無し][通常論文]
  • 小宮祐治, 遠藤三郎, 飯本武志, 石川正純, 杉浦紳之, 小佐古敏荘 理工学における同位元素・放射線研究発表会要旨集 41st 67 2004年07月 [査読無し][通常論文]
  • 高辻俊宏, 松瀬美智子, 中沢由華, 星正治, 高田純, 石川正純, 遠藤暁, 野島久美恵, 古沢佳也 NIRS-M (Natl Inst Radiol Sci) (173) 154 -155 2004年04月 [査読無し][通常論文]
  • Y. Onizuka, S. Endo, M. Ishikawa, M. Hoshi, S. Sakurai, T. Kobayashi, H. Utsumi, N. Hayabuchi, T. Takatsuji, H. Yamaguchi, M. Takada, K. Fujikawa, N. Maeda, K. Tanaka KURRI Progress Report 136 2004年04月01日 [査読無し][通常論文]
  • 高辻俊宏, 松瀬美智子, 中沢由華, 星正治, 高田純, 石川正純, 遠藤暁, 野島久美恵, 古沢佳也 NIRS−M (Natl Inst Radiol Sci) (173) 154-155 2004年04月 [査読無し][通常論文]
  • 石川正純, 小野公二, 桜井良憲, 宇根崎博信, 古林徹, 小佐古敏荘 日本原子力学会春の年会要旨集 42nd 187 2004年03月11日 [査読無し][通常論文]
  • 平沢雅彦, 石川正純, 富谷武浩, 高橋浩之, 首藤経世, 森国城, 尾鍋秀昭, 野宮聖一郎 UTNL−R(東京大学大学院工学系研究科附属原子力工学研究施設) (0433) 1-2 2004年02月02日 [査読無し][通常論文]
  • S Endo, Y Onizuka, M Ishikawa, M Takada, Y Sakurai, T Kobayashi, K Tanaka, M Hoshi, K Shizuma RADIATION PROTECTION DOSIMETRY 110 (1-4) 641 -644 2004年 [査読無し][通常論文]
     
    Microdosimetric single event spectrum in a human body simulated by an acrylic phantom has been measured for the clinical BNCT field at the Kyoto University Reactor (KUR). The recoil particles resulting from the initial reaction and subsequent interactions, namely protons, electrons, alpha particles and carbon nuclei are identified in the microdosimetric spectrum. The relative contributions to the neutron dose from proton, alpha particles and carbon are estimated to be about 0.9, 0.07 and 0.3, respectively, four depths between 5 and 41 mm. We estimate that the dose averaged lineal energy, y(D) decreased with depth from 64 to 46 keV mum(-1). Relative biological effectiveness (RBE) of this neutron field using a response function for the microdosimetric spectrum was estimated to decrease from 3.6 to 2.9 with increasing depth.
  • 石川 正純, 足立 にれか, 岡本 浩一 社会技術研究論文集 2 (0) 362 -369 2004年 [査読無し][通常論文]
     
    Recently, the matter which betrays national reliance such as a illegal act by the large company greatly breaks out frequently. These matters are common in the point that a contravention was being done through the agreement at a Meeting. Therefore, paying attention to the decision procedure in the group decision making, it is necessary to clarify the proper decision procedure to control systematic violation. This research aims at building an experiment tool to examine a proper group decision making procedure. As the experiment tool, a numerical simulation by the computer is used and various ...
  • WATANABE Hiromitsu, KASHIWABARA Shoji, KASHIMOTO Naoki, UESAKA Toshihiro, KATOH Osamu, ISHIKAWA Masayori Journal of radiation research 44 (4) 373 -373 2003年12月15日 [査読無し][通常論文]
  • 渡辺敦光, 柏原昌次, 樫本尚樹, 上坂敏弘, 加藤修, 石川正純 日本放射線影響学会大会講演要旨集 46th 70 2003年10月06日 [査読無し][通常論文]
  • 渡辺敦光, 石川正純, 新田由美子, 藤本成明, 鈴木文男, 竹岡清二, 北川和英, 菅慎治, 両角真里子 広島大学原爆放射線医科学研究所年報 (44) 165-166,403-404 2003年09月 [査読無し][通常論文]
  • 早川式彦, 星正治, 高田純, 金隆史, 新田由美子, 石川正純, 川野徳幸, 峠岡康幸, 山内光利 広島大学原爆放射線医科学研究所年報 (44) 135-164,375-401 2003年09月 [査読無し][通常論文]
  • 石川正純, 小野公二, 宇根崎博信, 古林徹, 桜井良憲, 田中憲一, 遠藤暁, 星正治 KURRI KR (95) 48-52 2003年08月 [査読無し][通常論文]
  • 鬼塚昌彦, 遠藤暁, 石川正純, 桜井良憲, 古林徹, 高田真志, 前田直子, 早淵尚文, 高辻俊宏 KURRI KR (95) 53-58 2003年08月 [査読無し][通常論文]
  • K Shizuma, S Endo, M Hoshi, J Takada, M Ishikawa, K Iwatani, H Hasai, T Oka, S Fujita, T Watanabe, T Yamashita, T Imanaka JOURNAL OF RADIATION RESEARCH 44 (2) 133 -139 2003年06月 [査読無し][通常論文]
     
    Residual Eu-152 activities induced by neutrons from the Nagasaki atomic bomb were measured for nine mineral samples located up to 1,061 in in the slant range and one control sample at 2,850 in from the hypocenter. A chemical separation to prepare europium-enriched samples was performed for all samples, and gamma ray measurements were carried out with a low background well-type germanium detector. In this paper, the measured specific activities of Eu-152 are compared with activation calculations based on the DS86 neutron fluence and the 93Rev one. The calculated-to-measured ratios are also compared with those of Co-60 and Cl-36. The present results indicate that the measurements agree to the calculation within a factor of three as observed in the nuclear tests at Nevada. The activation level of environmental neutrons and the detection limit for Eu-152 are also discussed.
  • W Zhang, K Fujikawa, S Endo, M Ishikawa, M Ohtaki, H Ikeda, M Hoshi JOURNAL OF RADIATION RESEARCH 44 (2) 171 -177 2003年06月 [査読無し][通常論文]
     
    The relative biological effectiveness (RBE) of various energy neutrons produced from a Schenkel-type accelerator at the Research Institute for Radiation Biology and Medicine, Hiroshima University (HIRRAC), compared with Co-60 gamma-ray radiation was determined. The neutron radiations and gamma-ray radiation produced good linear changes in the frequency of micronuclei induced in the root-tip cells of Allium cepa onion irradiated as dry dormant seeds (seed assay) and seedlings (seedling assay) with varying radiation doses. Therefore the RBE for radiation-induced micronuclei can be calculated as the ratio of the slopes of the fitted linear dose response for the neutron radiations and the Co-60 gamma-ray radiation. The RBE values by seed assay and seedling assay decreased to 174 +/- 7, from 216 +/- 9, and to 31.4 +/- 1.0, from 45.3 +/- 1.3 (one standard error), respectively, when neutron energies increased to 1.0 MeV, from 0.2 MeV, in the present study. Furthermore, the ratio of the micronucleus induction rates of seed assay to seedling assay by gamma-ray radiation was much lower than that by neutron radiations.
  • 鬼塚昌彦, 遠藤暁, 高田真志, 石川正純, 上原周三, 早淵尚文, 前田直子, 静間清, 山口寛 NIRS−M (Natl Inst Radiol Sci) (166) 236-238 2003年04月 [査読無し][通常論文]
  • 鬼塚 昌彦, 遠藤 暁, 石川 正純 KURRI-KR (95) 53 -58 2003年03月04日 [査読無し][通常論文]
  • 石川 正純, 小野 公二, 宇根崎 博信 KURRI-KR (95) 48 -52 2003年03月04日 [査読無し][通常論文]
  • Wenyi Zhang, Satoru Endo, Masayori Ishikawa, Hideo Ikeda, Masaharu Hoshi Journal of Radiation Research 44 81 2003年03月01日 [査読無し][通常論文]
  • WY Zhang, S Endo, M Ishikawa, H Ikeda, M Hoshi JOURNAL OF RADIATION RESEARCH 44 (1) 81 -81 2003年03月 [査読無し][通常論文]
  • 足立 にれか, 石川 正純, 岡本 浩一 社会技術研究論文集 1 (0) 278 -287 2003年 [査読無し][通常論文]
     
    In Japanese society corporate scandals, such as systematic violation, were found out one after another, and they have made profound impact on the society for these years. Most of all, the fact that acts clearly regarded as illegal were accepted in such corporation increased public distrust of it. Among various factors which lead to systematic violation, we consider decision procedures as one of the most important factors. Since violations were accepted through formal meetings at JCO which caused criticality accident, it must be paid to attention that which procedure is taken in group decisi...
  • 石川 正純, 宇根崎 博信, 古林 徹 京都大学原子炉実験所学術講演会報文集 37 (0) 231 -234 2003年01月 [査読無し][通常論文]
  • 鬼塚 昌彦, 遠藤 暁, 石川 正純 京都大学原子炉実験所学術講演会報文集 37 (0) 241 -245 2003年01月 [査読無し][通常論文]
  • 石川正純, 小野公二, 桜井良憲, 小佐古敏荘 第12回東京大学原子力研究総合センターシンポジウム 平成15年 181-184 2003年 [査読無し][通常論文]
  • 石川正純, 宇根崎博信, 古林徹, 桜井良憲, 田中憲一, 遠藤暁, 星正治 京都大学原子炉実験所学術講演会報文集 37th 231-234 -234 2003年01月 [査読無し][通常論文]
  • 鬼塚昌彦, 遠藤暁, 石川正純, 桜井良憲, 古林徹, 山口寛, 前田直子, 早淵尚文, 高辻俊宏 京都大学原子炉実験所学術講演会報文集 37th 241-245 -245 2003年01月 [査読無し][通常論文]
  • 早川式彦, 星正治, ズマジーロフ ザクシバ, オルロフ マーク, カミドワ ローラ, 高田純, 石川正純, 川野徳幸, 新田由美子 広島大学原爆放射線医科学研究所年報 (43) 115-139,329-351 2002年12月 [査読無し][通常論文]
  • WY Zhang, S Endo, M Ishikawa, H Ikeda, M Hoshi JOURNAL OF RADIATION RESEARCH 43 (4) 397 -403 2002年12月 [査読無し][通常論文]
     
    The relative biological effectiveness (RBE) of mixed neutron and gamma-ray radiation emitted at a Cf-252 source at the Research Institute for Radiation Biology and Medicine, Hiroshima University, compared with Co-60 gamma-ray radiation was determined. The tissue-absorbed dose contribution of the accompanying gamma radiation was about 35.7% to the total tissue-absorbed dose from the Cf-252 mixed radiation. The Cf-252 mixed radiation and Co-60 gamma rays produced approximate linear changes in the frequency of micronuclei induced in root-tip cells of Allium cepa L. onion seedlings after irradiation as dry dormant seeds with varying absorbed doses in onion seeds. Therefore, the RBE for radiation-induced micronuclei was calculated as the ratio of the slopes for the Cf-252 mixed radiation and the Co-60 gamma rays. The deduced RBE value of Cf-252 mixed radiation to Co-60 gamma rays to induce micronuclei in dry dormant onion seed cells was about 90.5 +/- 3.6 (+/- 1sigma); the RBE of neutrons from the Cf-252 mixed radiation was about 150 +/- 6 (+/- 1sigma). Furthermore, the sensitivity ratio of the induction rate of micronuclei in dry dormant seeds to that in seedlings by neutrons from Cf-252 mixed radiation was significantly different from that by Co-60 gamma rays. From these results, we concluded that the repair efficiency of DNA damage induced by neutrons may be different from that by gamma rays.
  • 田中憲一, 古林徹, 桜井良憲, 中川義信, 石川正純, 星正治 理工学における同位元素・放射線研究発表会要旨集 39th 59 2002年06月20日 [査読無し][通常論文]
  • 鬼塚 昌彦, 遠藤 暁, 高田 真志, 石川 正純, 星 正治, 上原 周三, 松藤 成弘, 金井 達明, 山口 寛, 前田 直子, 早渕 尚文 医学物理 : 日本医学物理学会機関誌 = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 22 (0) 55 -58 2002年04月04日 [査読無し][通常論文]
  • 田中 憲一, 古林 徹, 櫻井 良憲, 中川 義信, 石川 正純, 星 正治 医学物理 : 日本医学物理学会機関誌 = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 22 (0) 218 -221 2002年04月04日 [査読無し][通常論文]
  • S Endo, E Yoshida, Y Yoshitake, WY Zhang, K Fujikawa, T Itoh, M Ishikawa, M Hoshi, K Shizuma JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 (4A) 2191 -2194 2002年04月 [査読無し][通常論文]
     
    The multi-foil activation method using (n,p) and (n,alpha) of threshold reactions coupled with the neural network technique is considered to determine the neutron spectra of the Cf-252 fission neutron source of the Research Institute for Radiation Biology and Medicine (RIRBM), Hiroshima University and a reactor at Kinki University (UTR-KINKI). Training data for the neural network were prepared from computational data sets of Monte Carlo calculation. The reproducibility of the calculated activities was verified to be within 15% of the experimentally determined activities. As it has been shown that the incident neutron spectrum of the 252Cf fission neutron source will reproduce the Maxwellian function, the reactor neutron spectrum of UTR-KINKI is successfully determined. A comparison with a previous evaluation of the reactor spectrum using an unfolding NEUPAC code is also given.
  • S Endo, E Yoshida, Y Yoshitake, WY Zhang, K Fujikawa, T Itoh, M Ishikawa, M Hoshi, K Shizuma JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 (4A) 2191 -2194 2002年04月 [査読無し][通常論文]
     
    The multi-foil activation method using (n,p) and (n,alpha) of threshold reactions coupled with the neural network technique is considered to determine the neutron spectra of the Cf-252 fission neutron source of the Research Institute for Radiation Biology and Medicine (RIRBM), Hiroshima University and a reactor at Kinki University (UTR-KINKI). Training data for the neural network were prepared from computational data sets of Monte Carlo calculation. The reproducibility of the calculated activities was verified to be within 15% of the experimentally determined activities. As it has been shown that the incident neutron spectrum of the 252Cf fission neutron source will reproduce the Maxwellian function, the reactor neutron spectrum of UTR-KINKI is successfully determined. A comparison with a previous evaluation of the reactor spectrum using an unfolding NEUPAC code is also given.
  • 田中憲一, 古林徹, 桜井良憲, 中川義信, 石川正純, 星正治 日本原子力学会春の年会要旨集 40th 191 2002年03月05日 [査読無し][通常論文]
  • Y Onizuka, S Endo, M Ishikawa, M Hoshi, M Takada, T Kobayashi, Y Sakurai, H Utsumi, S Uehara, N Hayabuchi, N Maeda, T Takatuji, K Fujika RADIATION PROTECTION DOSIMETRY 99 (1-4) 383 -385 2002年 [査読無し][通常論文]
     
    Microdosimetric spectra ere measured in order to gain the nucrodosimetric parameters of some epithermal neutron fields. Changes in dose mean lineal energy y(D) as a function of depth of heavy water showed a trend of softening with heavy water of the beam. The neutron absorbed dose was obtained by using the frequency mean lineal energy, Results show good agreement with measurements with the activation method using gold foil. This study demonstrated how microdosimetric parameters change in radiation quality as a function of heavy water depth.
  • Kenichi Tanaka, Tooru Kobayasm, Yoshinori Sakurai, Yoshinobu Nakagawa, Masayori Ishikawa, Masaharu Hosm Journal of Nuclear Science and Technology 39 1290 -1293 2002年 [査読無し][通常論文]
     
    The validity of the simulation calculation method consisting of the Lee’s calculation for near-threshold 7Li(p, n)7Be and MCNP-4B for the neutron transport was verified with the experiments where the distance between the Li target and the EbO-filled human head phantom (T-P distance) was changed to consider the angular dependency. As a result, the saturated activity of Au in the phantom agreed between the calculation and the experiment in this study in the uncertainty of around 20 %. It was found that this simulation calculation method could simulate the distributions of the neutron intensity in the phantom, and the changes of the intensities by the proton energy difference and by the T-P distance. It was also found that the experiment to measure the intensity distributions of the neutrons in the phantom for various T-P distances could become a simple method to validate a simulation calculation with respect to the yield and the angular dependency of the neutrons. © 2014 Atomic Energy Society of Japan.
  • S. Endo, E. Yoshida, H. Nikjoo, S. Uehara, M. Hoshi, M. Ishikawa, K. Shizuma Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 194 (2) 123 -131 2002年 [査読無し][通常論文]
     
    A code is described for simulation of protons (100 eV to 10 MeV) track structure in water vapor. The code simulates molecular interaction by interaction for the transport of primary ions and secondary electrons in the form of ionizations and excitations. When a low velocity ion collides with the atoms or molecules of a target, the ion may also capture or lose electrons. The probabilities for these processes are described by the quantity cross-section. Although proton track simulation at energies above Bragg peak (> 0.3 MeV) has been achieved to a high degree of precision, simulations at energies near or below the Bragg peak have only been attempted recently because of the lack of relevant cross-section data. As the hydrogen atom has a different ionization cross-section from that of a proton, charge exchange processes need to be considered in order to calculate stopping power for low energy protons. In this paper, we have used state-of-the-art Monte Carlo track simulation techniques, in conjunction with the published experimental and established theoretical data, to develop a model for the extension of the proton track simulation to the low energy region. Data are presented on charge-state-fraction, proton stopping power, range and averaged energy producing an ion pair (W-values) in a mixture of hydrogen (H2) and Oxygen (O2/2) gas. The results are compared with the published experimental data. © 2002 Elsevier Science B.V. All rights reserved.
  • S Endo, M Takada, M Ishikawa, M Hoshi, S Uehara, H Yamaguchi, T Kanai, N Matsufuji, K Shizuma, Y Onizuka RADIATION PROTECTION DOSIMETRY 99 (1-4) 421 -424 2002年 [査読無し][通常論文]
     
    Single event spectra. of a clinical carbon beam have been measured by an ultra-miniature tissue-equivalent proportional counter (UMC). In order to cover the energy range of the Bragg peak the incident energy of the carbon beam as degraded by aluminium plates. Single event spectra for carbon-events incident to the UMC were analysed and selected at several carbon energies using thin scintillation counters. It as found that the dose weighted lineal energy distributions have a doublet peak structure due to incident carbon beam and fragment contributions.
  • 田中憲一, 古林徹, 桜井良憲, 中川義信, 石川正純, 星正治 京都大学原子炉実験所学術講演会報文集 36th 140-145 -145 2002年01月 [査読無し][通常論文]
  • 渡辺敦光, 石川正純, 田内広, 小松賢志, 竹岡清二, 北川和英, 管慎治, 両角真里子 広島大学原爆放射能医学研究所年報 (42) 139-140,391-393 2001年12月 [査読無し][通常論文]
  • M Ishikawa, T Kobayashi, Y Sakurai, K Kanda JOURNAL OF RADIATION RESEARCH 42 (4) 387 -400 2001年12月 [査読無し][通常論文]
     
    Because background radiation in an irradiation room creates a problem with the PG-SPECT (Prompt Gamma-ray Single Photon Emission Computed Tomography) system, which evaluates the absorbed dose for the Boron Neutron Capture Therapy treatment, optimization of a collimator system was performed while taking the shielding of background gamma-rays into consideration. Assuming that a parallel-beam collimator is used, three parameters - the diameter of a hole, the length of the collimator, and the number of detectors (the number of holes of the collimator) - were selected for optimization. Because the combinations of these parameters are limitless, it is difficult to determine them simultaneously. Therefore, a statistically derived Optimization Criterion has been proposed to optimize these parameters. When the spatial resolution was 1 cm-FWHM (full width at half maximum), the optimal diameter of the collimator was 5.4 mm, the optimal length was 321 mm, and the optimal number of detectors was 31 x 31.
  • IMANAKA Tetsuji, HOSHI Masaharu, ISHIKAWA Masayori, TAKADA Jun, SHIZUMA Kiyoshi, ENDO Satoru, IWATANI Kazuo, OKA Takamitsu, FUJITA Shoichiro, HASAI Hiromi Journal of radiation research 42 (4) 473 -473 2001年12月 [査読無し][通常論文]
  • J Takada, S Suga, K Kitagawa, M Ishikawa, S Takeoka, M Hoshi, H Watanabe, A Ito, N Hayakawa JOURNAL OF RADIATION RESEARCH 42 (1) 47 -55 2001年03月 [査読無し][通常論文]
     
    A beta-ray survey was carried out on concrete walls of the boundary and buildings after a criticality accident at a factory of JCO Co. Ltd. at Tokai-mura. A remarkable distribution of beta counts was observed on the walls depending on the complex internal and external structures of buildings surrounding a precipitation vessel containing uranium 23 days after the accident. The directional distribution function, based on the beta counts on the walls, aias consistent with data concerning the neutron dose rate measured in several directions during the accident, suggesting an anisotropic neutron distribution to the residential area.
  • Masayori Ishikawa, Tooru Kobayashi, Keiji Kanda Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 453 (3) 614 -620 2000年10月 [査読無し][通常論文]
     
    In order to reduce the standard deviation in counting prompt γ-rays emitted from10B(n,αγ)7Li reactions at Prompt Gamma-ray Single Photon Emission Computed Tomography (PG-SPECT) system, statistical estimation using a Maximum Likelihood Estimation (MLE) is proposed. The measured energy spectrum was analyzed statistically with MLE based on the ideal energy spectrum. The standard deviation of counting was estimated using 20000 energy spectra including background γ-rays, generated with a Monte Carlo method on a personal computer. When the S/N ratio is lower than 0.1, the standard deviation of the method presented here, i.e. the Maximum Likelihood Estimation of Spectrum (MLES), was reduced by up to approximately 20% compared to the conventional Triple Energy Window (TEW) method.
  • 竹岡清二, 菅慎治, 北川和英, 両角真里子, 石川正純, 星正治 生理学技術研究会報告 (22) 94-96 2000年10月 [査読無し][通常論文]
  • 高田純, 菅慎治, 北川和英, 石川正純, 星正治 日本放射線影響学会大会講演要旨集 43rd 56 2000年08月21日 [査読無し][通常論文]
  • 白石久二雄, 木村真三, 米原英典, 高田純, 石川正純, 五十嵐康人, 青山道夫, 中島敏行, 小村和久 日本放射線影響学会大会講演要旨集 43rd 104 2000年08月21日 [査読無し][通常論文]
  • 高田純, 菅慎治, 北川和英, 石川正純, 星正治 理工学における同位元素研究発表会要旨集 37th 196-199 2000年06月20日 [査読無し][通常論文]
  • 菅慎治, 石川正純, 竹岡清二 分子科学研究所技術研究会報告 (16) 60-63 2000年06月 [査読無し][通常論文]
  • 遠藤暁, 石川正純, 星正治, 静間清 医学物理 20 (Supplement 2) 34-35 2000年04月06日 [査読無し][通常論文]
  • 吉川勲, 高辻俊宏, 星正治, 高田純, 遠藤暁, 石川正純 NIRS−M (Natl Inst Radiol Sci) (139) 159-162 2000年04月 [査読無し][通常論文]
  • 田中英夫, 石川正純, 竹岡清二, 木口雅夫 Innervision 15 (2) 41-43 2000年02月 [査読無し][通常論文]
  • K Komura, M Yamamoto, T Muroyama, Y Murata, T Nakanishi, M Hoshi, J Takada, M Ishikawa, S Takeoka, K Kitagawa, S Suga, S Endo, N Tosaki, T Mitsugashira, M Hara, T Hashimoto, M Takano, Y Yanagawa, T Tsuboi, M Ichimasa, Y Ichimasa, H Imura, E Sasajima, R Seki, Y Saito, M Kondo, S Kojima, Y Muramatsu, S Yoshida, S Shibata, H Yonehara, Y Watanabe, S Kimura, K Shiraishi, T Ban-nai, SK Sahoo, Y Igarashi, M Aoyama, K Hirose, T Uehiro, T Doi, A Tanaka, T Matsuzawa JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 50 (1-2) 3 -14 2000年 [査読無し][通常論文]
     
    A criticality accident occurred on September 30, 1999 at the uranium conversion facility of the JCO Company Ltd. in Tokai-mura, Japan. A collaborating scientific investigation team was organized in two groups, the first to carry out research on the environmental impact (the environmental research group) and the second to assess the radiation effects on residents (the biological research group). This report concerns only the activities of the environmental research group. Four investigative teams were sent on different dates to the accident site and its vicinity to collect samples. About 400 samples were collected and subjected to analysis. An outline of the sampling campaign is presented here along with a brief chronology of the accident and the preliminary key results obtained by the independent research group are summarised in this Special Issue of the Journal of Environmental Radioactivity. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • S Endo, N Tosaki, K Shizuma, M Ishikawa, J Takada, S Suga, K Kitagawa, M Hoshi JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 50 (1-2) 83 -88 2000年 [査読無し][通常論文]
     
    Stainless-steel (SS) samples activated by fission neutrons from the JCO criticality accident have been measured by low-background germanium spectrometers. The SS-samples, comprising 14 spoons and 4 other items, were collected from residences located at 130-700 m from the JCO site. Five SS-samples from within a ground distance of 400 m from JCO were identified as containing Cr-51 activity, which was produced by the Cr-50(n, gamma)Cr-51 reaction. The chromium specific activities of Cr-51/Cr are preliminarily obtained to be 0.45-0.04 Bq/g-Cr for the 5 samples collected at 130-400 m distance. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • Tooru Kobayashi, Yoshinori Sakurai, Masayori Ishikawa Medical Physics 27 (9) 2124 -2132 2000年 [査読無し][通常論文]
     
    A noninvasive method for measuring the absorbed dose distribution during the administration of clinical boron neutron capture therapy (BNCT) using an online three-dimensional (3D) imaging system is presented. This system is designed to provide more accurate information for treatment planning and dosimetry. The single-photon emission computed tomography (SPECT) technique is combined with prompt gamma-ray analysis (PGA) to provide an ideal dose estimation system for BNCT. This system is termed PG-SPECT. The fundamental feasibility of the PG-SPECT system for BNCT is confirmed under the following conditions: (1) a voxel size of 1 x 1 x 1 cm3, comparable to the spatial resolution of our standard dosimetric technique using gold wire activation, where data are available for every 5-10 mm of wire length (2) a reaction rate of 10B(n, α)7Li within the measurement volume is greater than 1.1 x 106 interactions/cm3/s, corresponding to a thermal neutron flux of 5 x 108 n/cm2/s and a 10B concentration of greater than 10 ppm for the deepest part of the tumor volume under typical BNCT clinical conditions (3) statistical uncertainty of the count rate for 10B(n, α)7Li prompt gamma rays is 10% or less. The desirable characteristics of a detector for the PG-SPECT system were determined by basic experiments using both HPGe and CdTe semiconductor detectors. The CdTe semiconductor detector has the greatest potential for this system because of its compactness and simplicity of maintenance. (C) 2000 American Association of Physicists in Medicine.
  • Takada J., Suga S., Kitagawa K., Ishikawa M., Hoshi M. Journal of radiation research 41 (4) 378 -378 2000年
  • SHIRAISHI Kunio, KIMURA Shinzo, YONEHARA Hidenori, TAKADA Jun, ISHIKAWA Masayori, IGARASHI Yasuhito, Aoyama Michio, NAKAJIMA Toshiyuki, KOMURA Kazuhisa Journal of radiation research 41 (4) 491 -491 2000年
  • The Investigation of the Under-surgery Irradiation of NCT using Near-threshold 7Li(p,n)7Be Neutrons
    K.Tanaka, T.Kobayashi, Y.Sakurai, Y.Nakagawa, M.Ishikawa, S.Endo, M.Hoshi 9th International Symposium on Neutron Capture Therapy\n 49 -50 2000年 [査読無し][通常論文]
  • Prompt Gamma Ray Measurement in the KUR Irradiation Room by Cd-Zn-Te Semiconductor Detector for PG-SPECT
    T.Kobayashi, M.Ishikawa, Y.Sakurai 9th International Symposium on Neutron Capture Therapy\n 77 -78 2000年 [査読無し][通常論文]
  • Preliminary Study on 2-dimensional Distributions of 10B Reaction Rate in a Water Phantom with Boron-doped CR-39 for 7Li(p,n)7Be Neutrons by 1.95 MeV Protons
    Y.Hasegawa, K.Tanaka, T.Kobayashi, Y.Sakurai, M.Ishikawa, M.Hoshi, T.Tsuruta 9th International Symposium on Neutron Capture Therapy\n 279 -280 2000年 [査読無し][通常論文]
  • Microdosimetry of Epithermal Neutron Beam
    Y.Onizuka, S.Uehara, S.Endo, M.Ishikawa, J.Takada, M.Hoshi, Y.Sakurai, T.Kobayashi, H.Ustumi, N.Hayabuchi, T.Takatsuji, H.Yamaguchi, M.Takada, K.Fujikawa, N.Maeda 9th International Symposium on Neutron Capture Therapy\n 265 -266 2000年 [査読無し][通常論文]
  • 古林徹, 桜井良憲, 田中憲一, 石川正純 京都大学原子炉実験所学術講演会報文集 34th 30-35 2000年01月 [査読無し][通常論文]
  • M Hoshi, S Endo, J Takada, M Ishikawa, Y Nitta, K Iwatani, T Oka, S Fujita, K Shizuma, H Hasai JOURNAL OF RADIATION RESEARCH 40 (Suppl.) 145 -154 1999年12月 [査読無し][通常論文]
     
    There has been a large discrepancy between the Dosimetry system 1986 (DS86)(1)) and measured data, some of which data in Hiroshima at about 1.5 km ground distance from the hypocenter are about 10 times larger than the calculation. Therefore its causes have long been discussed(2-10)), since it will change the estimated radiation risks obtained based on the Hiroshima and Nagasaki data. In this study the contradiction was explained by a bare-fission-neutron leakage model through a crack formed at the time of neutron emission. According to the present calculation, the crack has a 3 cm parallel spacing, which is symmetric with respect to the polar axis from the hypocenter to the epicenter of the atomic bomb. We made also an asymmetric opening closing 3/4 of this symmetric geometry, because there are some data which shows asymmetry(5,12,13)). In addition, the height of the neutron emission point was elevated 90 m. By using the asymmetric calculation, especially for long distant data located more than 1 km, it was verified that all of the activity data induced by thermal and fast neutrons, were simultaneously explained within the data scattering. The neutron kerma at a typical 1.5 km ground distance increases 3 and 8 times more than DS86 based on the symmetric and asymmetric model, respectively.
  • SHIBATA Seiichi, TAKAMIYA Koichi, NAKAGAWA Takuji, HOSOYA Yuichi, SHINOHARA Atsushi, SHIBATA Tokushi, ITOH Yutaka, IMAMURA Mineo, NOGAWA Norio, SHIZUMA Kiyoshi Journal of radiation research 40 (4) 364 -364 1999年12月 [査読無し][通常論文]
  • 石川 正純, 古林 徹, 神田 啓治 放射線医学物理 60 (0) 75 -75 1999年04月 [査読無し][通常論文]
  • 石川正純, 古林徹, 神田啓治 日本原子力学会春の年会要旨集 36th 135 1998年03月 [査読無し][通常論文]
  • 西畑敏伸, 石川正純, 鈴木亮輔, 小野勝敏 材料とプロセス 9 (3) 468 1996年03月 [査読無し][通常論文]
  • SHIZUMA Kiyoshi, IWATANI Kazuo, HASAI Hiromi, OKA Takamitsu, HOSHI Masaharu, IMANAKA Tetsuji, SHIBATA Tokushi, SHIBATA Seiichi, IMAMURA Mineo Journal of radiation research 36 (4) 320 -320 1995年12月 [査読有り][通常論文]
  • SHIZUMA Kiyoshi, IWATANI Kazuo, HASAI Hiromi, OKA Takamitsu, HOSHI Masahuru, SHIBATA Tokushi, SHIBATA Seiichi, IMAMURA Mineo Journal of radiation research 35 (4) 332 -332 1994年12月 [査読無し][通常論文]
  • T SHIBATA, M IAMMURA, S SHIBATA, Y UWAMINO, T OHKUBO, S SATOH, N NOGAWA, H HASAI, K SHIZUMA, K IWATANI, M HOSHI, T OKA JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 63 (10) 3546 -3547 1994年10月 [査読無し][通常論文]
     
    A new method to estimate the fast-neutron fluence of the Hiroshima atomic bomb is proposed. Ni-63 produced by the Cu-63(n,p)Ni-63 reaction provides a unique measure by which to estimate the fast-neutron fluence of the Hiroshima/Nagasaki atomic bombs, because the half-life of Ni-63 is 100 years and 70% of the Ni-63 produced in a copper piece presently exists after 50 years. Using the neutron spectrum given in DS86 and the estimated cross section, we found that a piece of copper of about 10 g which was exposed at a point around 100 m from the hypocenter gives a measurable amount of Ni-63 using a low-background liquid scintillation counter. For the measurement of Ni-63, accelerator mass spectrometry also seems to be applicable.

書籍等出版物

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2024年04月 -2027年03月 
    代表者 : 足利 雄一, 鈴木 崇祥, 石川 正純, 若林 侑輝
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2023年04月 -2026年03月 
    代表者 : 石川 正純
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2019年04月 -2023年03月 
    代表者 : 石川 正純, 小川原 亮
     
    加速器BNCTでは、熱外中性子を主たる成分として照射することから、熱外中性子照射量をモニタできる検出器の開発が望まれている。そこで本研究では、熱中性子照射量をリアルタイムで測定可能なSOF検出器を改良し、異なる中性子増感物質を含むシンチレータを組み合わせることにより、熱中性子量、熱外中性子量、ガンマ線量を同時に評価することが可能な新たなSOF検出器を開発する。 マルチコア型SOF検出器に適した中性子増感物質および化合物を選定し、有効な発光量を得るためにnmオーダーまで微細化した粉末を用いたプローブを作成したが、期待した信号量（発光量）が得られなかった。そこで、プラスチックシンチレータ発光の時間変化が荷電粒子の種類に応じて変化することを利用し、PQD（Peak to charge discrimination）法を用いて対象となる反応のみを抽出する方法を試みた。PQDヒストグラムを作成したところ、成分が分かれることは確認されたが、シミュレーションによる計算とは十分には一致しない結果となった。一方、BNCTでは患部におけるホウ素（B-10）濃度も治療効果に大きく影響する。現在、患部への集積度を18F-BPA PET画像から評価しているが、血中ホウ素濃度との相関関係は患者に依存する。そこで本研究では、18F-BPA PET撮像中に同時に血中ホウ素濃度を測定するための腕部装着可能な小型PET装置を開発し、血中ホウ素濃度とPET画像による評価の相関関係を患者個別に構築できるシステムを開発を目指している。本研究で開発する腕部装着型PET装置のためのDOI検出器開発では、最低32チャンネルの高速信号処理回路が必要となることから、16チャンネル分の汎用高速計測ボードを購入し、アナログフロントエンド回路の開発を行った。
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    研究期間 : 2017年04月 -2023年03月 
    代表者 : 作原 祐介, 石川 正純, 曽山 武士, 阿保 大介
     
    これまで、X線透視装置(アンダーチューブ、オーバーチューブ)を用い、実際の臨床における様々な状況を想定した条件設定における、X線透視下の手技におけ る術者被ばく線量の計測実験を、患者ファントム、術者ファントム、リアルタイム線量計、熱ルミネッセンス線量計、を使用して行ってきた。 天吊型の遮蔽板や、エプロン/カーテン型といった、面積が比較的広い遮蔽物の防護効果は高いが、顔面の一部を覆う被ばく防護メガネの遮蔽効果は、当初の想 定よりも低い結果が判明した。過去に公表されている学会発表や論文データでは、被ばく防護メガネの高い有効性が報告されているが、我々の実験結果はこれら を下回るものだった。 過去の研究の計測方法は、多くが被ばく防護メガネのレンズの表裏に線量計を貼付しているのに対し、我々は術者頭部ファントムの眼球部分に線量計を設置して 測定している。そのため、レンズの直近では被ばく線量が低下するものの、レンズから離れた位置にある眼球は、上・下顎方向や側頭部方向からのX線による被 ばくによって、レンズの直近よりも線量が高くなっている可能性があるのではないかと推測している。この場合、レンズの直近に貼付した線量計の結果は、実際 の水晶体の被ばくを反映していないことになり、被ばく推定値として信頼できないことになる。 現在、我々の実験結果と、過去の研究報告との乖離がある部分について、上記の推測が正しいかどうかを検証する必要があると考えており、追加実験の条件設定、空間線量分布シミュレーションの方法について再検討している。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 石川 正純, 鈴木 隆介, 橋本 成世
     
    本研究の目的は、放射線治療におけるフィルムを用いた線量分布評価法として、線量勾配を考慮した新しい解析方法であるGradient法を確立することである。一般的に、放射線計測はポアソン統計に従うことから、統計学に基づいた判定基準を提案した。統計学的な評価を可能とするために、測定に起因する不確かさおよび位置ずれに起因する不確かさを評価する手法を開発し、複数の施設にて実測による検証を行った。
  • 日本学術振興会：科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 田中 真樹, 國松 淳, 竹谷 隆司, 石川 正純, 宮本 直樹
     
    実験動物の特定の脳部位に比較的広範な障害を作成する技術は、脳の機能を調べる基本的なツールになりうる。本研究ではそのひとつとして放射線照射の実用性を検討するとともに、新たな行動および電気生理学的な指標の開発を行い、さらには放射線照射以外の脳深部への破壊巣作成法の検討を行った。前頭葉皮質に放射線照射を行ったサルの眼球運動を最長8か月間評価し、その障害の経時変化を明らかにした。また、小脳や大脳基底核の病変を検知するための行動指標の開発を行った。新しい障害作成法として、化学遺伝学の手法を用いた可逆的な機能脱落を目指してサル小脳への遺伝子導入を試みた。今後の研究につながる貴重な情報を得ることができた。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2012年04月 -2015年03月 
    代表者 : 星 正治, 鬼塚 昌彦, 遠藤 暁, 石川 正純, 佐藤 斉, 大瀧 慈, 濱野 毅, 須田 充, 鎌田 創, 高田 真志, 田中 憲一, 山河 享平, 東又 厚, 新井 誠司, ズマジーロフ カシム
     
    がんの放射線治療には、X線、ガンマ線、陽子線等が使われている。本研究では新しく中性子を使った方法の開発を行った。ホウ素中性子捕獲量法(BNCT)と言う。ホウ素をがんに取り込ませ、そのホウ素に中性子を照射する。そしてホウ素からアルファ線を発生させ、がんを治療する。そのアルファ線の到達距離が短く、がん細胞1個1個の治療が可能である。従来の方法は外科治療のようにがんの塊を焼くことに対応するが、本方法は悪性脳腫瘍のようにがんが良性の細胞にしみこんだ場合に有効である。従来原子炉を使っていたが、小型の加速器を開発し広く病院に設置されることを最終目的としている。本研究ではターゲットと測定器の開発を行った。
  • 日本学術振興会：科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2012年04月 -2014年03月 
    代表者 : 田中 真樹, 石川 正純, 國松 淳, 宮本 直樹
     
    実験動物の脳に治療用放射線の定位照射を行い、脳疾患モデルを作成することを試みた。３頭のニホンザルの右半球の前頭眼野を中心とした領域に計4回の照射を行った（130-150 Gy）。照射後数週間は浮腫が著明であり、行動指標として用いた眼球運動にも軽度の変化が認められたが、１か月程度の経過でMRI所見、行動ともに照射前のレベルに落ち着いた。1頭で約8か月にわたって観察を続けたところ、照射後4か月頃から後期障害が現れた。組織学的には白質を中心とした壊死巣と周囲の出血が認められたが、灰白質は層構造が保たれていた。今後はこの技術を脳深部に適用するとともに、低用量の照射で長期観察を行う。
  • 文部科学省：科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2012年 -2012年 
    代表者 : 石川 正純
     
    本研究の目的は、放射線治療における腫瘍近傍の体内マーカに非接触での積算線量計の機能を持たせた新たな体内マーカを開発することである。放射線照射によって誘電体の静電容量が変化することを利用し、体内に埋め込まれたマーカの共振周波数を測定することにより、マーカに照射された線量を非接触で測定できると考えた。アンテナコイルとネットワークアナライザを用いて、非接触でコンデンサの静電容量を測定し、1pF～100nFという非常に広い範囲においてLCRメータを用いた測定と近い数値が得られた。また、シミュレーションの結果から、20cm離れた位置でも信号が読み出せることを確認した。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2010年 -2012年 
    代表者 : 金子 純一, 藤田 文行, 鹿田 真一, 笹尾 真美子, 佐藤 聡, 磯部 光孝, 中井 光男, 浅野 芳裕, 石川 正純
     
    単結晶CVDダイヤモンドの合成条件を最適化した。合成結晶から検出器を製作しα線を使用した誘導電荷量分布測定を行った。その結果、電荷取集効率:100%(正孔)、97%(電子)、μτ積:1×10-4(正孔)、9.6×10-6(電子)cm2/Vを得た。これらの検出器を用い14MeV中性子応答関数測定を行った結果、12C(n,alpha)9Be反応によって生じたピークのエネルギー分解能:3.5%を達成した。また、8GeV電子ビームを使用した時間応答測定では350psの時間分解能を達成した。
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2009年 -2012年 
    代表者 : 白土 博樹, 本間 さと, 玉木 長良, 芳賀 永, 但野 茂, 石川 正純
     
    放射線を軸に、ナノレベルの物理現象から社会的存在としての患者まで生体の動体追跡科学の基盤研究を行った。電子線トラック特性解析から細胞生存率モデルを提案した。DNAの二本鎖切断のうち修復されずに残るものの数がPoisson分布し、それが潜在的致死(PL)損傷であると仮定するNLP(Non-Lethal Probability)モデルによって、照射後の細胞の生存率をより適切に説明できた。細胞への放射線効果の予測を統計学的に行う際には、解析対象を分布値で表現する解析法を導入することで、より正しく記述できることが示唆された。ひと由来がん細胞が軟らかい基盤上の動きを観察したところNF-κBやLOXとの関係がわかり、細胞のゲル器質内への侵潤の3次元的観察系を構築する基礎が整った。マウス体内の各部位における遺伝子発現をリアルタイムに長期間、自由行動中の動物から計測する小動物内の分子の動体追跡技術を開発した。ルシフェラーゼレポーターを用い、体表からの微弱発光レベルの三次元空間における長期間追跡を行うことができ、定量的追跡への土台が整った。サルの脳定位照射・動体追跡照射の実験を可能にするために、準備的検討を行った。大動物の動体追跡実験が可能になると、生理学的検討に使える可能性が高い。ひとがん組織の放射線治療後の腫瘍の変化を定量的に記載し、予測するためのモデルを構築した。ひとがん腫瘤の動体追跡の...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2009年 -2011年 
    代表者 : 星 正治, Zhumadiov kassym, 遠藤 暁, 石川 正純
     
    1.前年度、ターゲット冷却システムの設計と製作を行った。水冷法であり銅にリチウムを蒸着または貼り付け、その銅を後方から水で冷却する。水と接する面は平面である。陽子は2.5MeV,20mA陽子による50kWの発熱に対しては十分な冷却が出来ない。構造解析コードを用いて、ターゲットの熱および寿命と構造材の強度に着目した冷却システムを検討し、設計し製作した。そのなかにはLiターゲットの寸法や冷却水の流路の寸法、流速などの検討が含まれる。設計した冷却システムについて、照射場のBNCT適用性を、中性子γ線輸送計算コードPHITSを用いて計算を行った。2.中性子発生装置は放射線医学総合研究所の3MV,2mA静電型陽子線加速器で6回試験した。また線量計測のため、IC-17,IC-17G電離箱を購入し放医研のCo-60照射装置で測定した。結果は良好であった。3.今後購入したボロン入りのポリエチレン(IC-17PB)とボロンの入っていないポリエチレン(IC-17P)の電離箱でも校正と測定を行う。これらは新たに考案した4電離箱方式で、(1)速中性子、(2)熱中性子、(3)ガンマ線、(4)(n,a)反応の線量をリアルタイム測定で可能にするためである。そのためPHITSコードを使った計算を行い可能であることを計算している。4.また、より小型のIC-18シリーズで同様の計測法の開発を進める。SOF検出器...
  • 文部科学省：科学研究費補助金(若手研究(A))
    研究期間 : 2007年 -2009年 
    代表者 : 石川 正純
     
    光ファイバの先端に極微小シンチレータを取り付けた光ファイバ線量計について、線量計として機能するための基礎理論を確立し、論文として纏めた。Ir-192高線量率密封小線源を用いた前立腺癌の治療において、過線量投与による尿道狭窄を予防する目的として、11例の患者に対して線量測定を行った。尿道内で最も線量が高くなると予想される箇所の線量をモニタリングし、治療計画と概ね一致した線量が投与されていることをリアルタイムで確認することに成功した。また、高エネルギーX線およびγ線での線量測定に対応できるようにするために、分光型光ファイバ線量計を検討し、分光波長の最適化及び実機の製作を行った。さらに、多点同時計測が可能な光ファイバ線量計システムの開発に着手し、最大192ch同時計測が可能なシステムを製作した。
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2007年 -2009年 
    代表者 : 本間 さと, 早坂 直人, 仲村 朋子, 早坂 直人, 浜田 俊幸, 石川 正純, 久保田 英博, 下川原 正博, 榎本 敏照
     
    本研究は、in vivoで、無麻酔・無拘束動物から時計遺伝子発現リズムを計測し、視交叉上核(SCN)に局在する哺乳類の中枢時計の行動リズム制御メカニズムを明らかにすることを目的として行った。時計遺伝子Per1プロモータ支配下に発光酵素ルシフェラーゼを発現するPer1-lucマウスを用い、自発行動量と光ファイバーによるSCNの時計遺伝子発現を同時計系を構築し、1分毎の連続測定を行った。その結果、SCN、嗅球いずれからも、安定したPer1-lucのフリーランリズムが計測された。さらに、光同調や位相反応を示すことから、内因性振動を反映していることが確認できた。
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2006年 -2008年 
    代表者 : 白土 博樹, 本間 さと, 玉木 長良, 鬼柳 善明, 畠山 昌則, 金子 純一, 久下 裕司, 伊達 広行, 水田 正弘, 犬伏 正幸, 但野 茂, 田村 守, 早川 和重, 松永 尚文, 石川 正純, 青山 英史, 作原 祐介, 鬼丸 力也, 阿保 大介, 笈田 将皇, 神島 保, 寺江 聡, 工藤 與亮, 小野寺 祐也, 尾松 徳彦, 清水 伸一, 西村 孝司, 鈴木 隆介, ジェラード ベングア
     
    いままでの先端放射線医療に欠けていた医療機器と患者のinteractionを取り入れた放射線治療を可能にする。臓器の動き・腫瘍の照射による縮小・免疫反応などは、線量と時間に関して非線形であり、システムとしての癌・臓器の反応という概念を加えることが必要であることが示唆された。生体の相互作用を追求していく過程で、動体追跡技術は先端医療のみならず、基礎生命科学でも重要な役割を果たすことがわかった。
  • 文部科学省：科学研究費補助金(若手研究(A))
    研究期間 : 2004年 -2006年 
    代表者 : 石川 正純
     
    2006年度現在、国内で唯一ホウ素中性子捕捉療法が行われている日本原子力研究開発機構にリアルタイム熱中性子モニタ(SOF検出器)を配備した。同時に複数箇所で測定が行えるようにするために、測定回路系の仕様変更を行い、同時に8箇所の熱中性子束測定が行えるシステムを完成させた。その結果、現在のところ、2箇所での同時測定を行い、1箇所は患者の動き等の影響を受けないコリメータ内側に配置、もう一箇所は患者表面へ貼り付けて測定を行うことが可能となった。臨床において実際の症例に対して計30回以上のリアルタイム熱中性子束計測を行い、従来の熱中性子束評価法と比較してほぼ同等の計測値が取得でき、SOF検出器の有効性を確認した。また、治療計画装置JCDSで計算された線量分布・熱中性子束分布に、SOF検出器によるリアルタイム熱中性子束を反映させることによって、リアルタイムでの各種線量分布、中性子束分布を3次元で確認することが出来るソフトウェアを開発した。開発したソフトウェアでは、患者の体輪郭構造が分かるように、CT画像データ上に線量分布・中性子束分布を重ね合わせて表示できるように工夫を施した。これらの分布は、SOF検出器による測定値に連動して、1秒単位で更新されるため、リアルタイムでの線量分布評価が可能となった。したがって、患者のあらゆる箇所における線量を照射中に確認することが出来るため、過剰線量およ...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2002年 -2005年 
    代表者 : 遠藤 暁, 小島 康明, 星 正治, 静間 清, 石川 正純
     
    マイクロビームラインを有しないビームラインにおいてマイクロビームPIXEと同程度以上の位置分解能のPIXE2次元元素マッピングができる可能性を有する新しいPIXE分析技術(SPECT手法を併用したPIXE分析法:以下SPECT-PIXE分析法と呼ぶ)の開発と確立を目指す。このために、(1)CdTe検出器によるPIXE測定が可能であること、なおかつ、(2)大気取出しした陽子線で測定が行えることを確かめる。(3)SPECT法を用いた測定器配置、ピンホールコリメータの設計のためにモンテカルロシミュレーションを行う。(4)コリメータの製作と性能評価を行った後、最適条件を決定する。これまでにCdTe検出器アレイを模擬したX線カメラを作成し測定シミュレーション行ってきた。実際のPIXE測定が実現した際にモニターとして用いる予定である。改良により初年度の500倍の感度向上が得られている。また、現在の手法による分解能は検出器表面において140μmの位置分解能が確認された。この値は、10:1の拡大率を持つピンホールコリメータを用いたときには、X線の位置分解能として14μmを与えることを確かめている。しかしながら、CdTe検出器のエネルギーの分解能は2keV程度で期待していた分解能より悪く、ショットキー型のCdTe検出器またはSi-ピンフォトダイオードの検出器アレイに変更する必要があることが示唆...
  • 文部科学省：科学研究費補助金(若手研究(B))
    研究期間 : 2002年 -2003年 
    代表者 : 石川 正純
     
    本研究は、ホウ素中性子捕捉療法における治療中の熱中性子束をリアルタイムで測定するための検出器であるSOF検出器(Schintillator with Optical Fiber Detector)の改良を目的としている。(1)検出器システムの小型化: SOF検出器システムは光電子増倍管、波形整形増幅器、波高弁別器、計数器といった一般的な機器で構成されていることから、従来のCAMACやNIMのモジュールを使用せずに、市販のフォトンカウンティングユニットをシステムに取り込むことによって、安定かつ小型なシステムの構築に成功した。(2)検出プローブの改良:昨年度までは、シンチレーションファイバと光ファイバを光学セメントで接続させて検出プローブを構成していたが、光学セメントの放射線耐性が良好ではないことから、液状固化タイプのプラスチックシンチレータ使用を検討した。液状固化タイプの場合、様々な核種の中性子増感剤を混入または塗布することによって、種々の検出プローブ作製が可能となる。これまで、ホウ酸(B-10濃縮度99%)および弗化リチウム(Li-6濃縮度95%)による熱中性子の検出を試み、いずれも有効な測定が可能であることを確認した。また、中性子増感剤をシンチレータ表面に塗布した検出プローブは、シンチレータに混入した場合に比べてより大きな発光量が得られるが、作製したプローブ間のバラツキは、...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2000年 -2002年 
    代表者 : 星 正治, 高田 純, 遠藤 暁, 石川 正純, 岩本 英司, 新田 由美子
     
    中性子の生物影響がガンマ線やベータ線よりも格段に大きい。中性子の影響が考えられるケースとして、広島・長崎の原爆被爆者、東海村の事故があげられる。中性子は人体に入ると、主な成分である水の中の水素の原子核である陽子をはじき飛ばす(反跳)。この反跳陽子は電荷を持つので水分の中ではラジカルを生成し、DNAなどに2重鎖切断などの損傷を与える。陽子の反跳の全線量に対する割合は中性子のエネルギーにより異なるが70-80%である。この反跳陽子の損傷はほとんど修復されるが、その一部が修復されずに残り、それが最終的にはがんなどの障害をもたらすと考えられている。最近その2重鎖切断が中性子では近傍に集中して起こりDNAが大きく損傷し修復できないとするクラスターモデルが提案されている。このほかに中性子は原子核反応を起こし、そこから発生する粒子線、ガンマ線、ベータ線などもある。この研究の目的はこの主たる放射線である陽子の影響を広島大学にあるシェンケル型加速器を使って陽子線を放出しそれをタマネギの根の先の細胞に照射しその影響を直接見ることであった。このための照射装置は完成出来たが、陽子線の強度の調整と、一様性の調整が間に合わないことが分かった。そのため、中性子を直接当てる実験を行った。照射はタマネギの発芽種子だけではなく乾燥種子にも行い、発芽し種の先の細胞に生じた小核を観察し、その発生率をコバルト60に対...
  • 文部科学省：科学研究費補助金(奨励研究(A))
    研究期間 : 2000年 -2001年 
    代表者 : 石川 正純
     
    現在行われているホウ素中性子捕捉療法では、患者の血中ホウ素濃度と治療中に測定した中性子束密度を用い、事前に行った実験や計算をもとに吸収線量を推測している。我々の研究グループでは、治療中にリアルタイムで吸収線量を直接評価するために、PG-SPECT(Prompt Gamma-ray Single Photon Emission Computed Tomography)システムを提案し、その開発に取り組んでいる。PG-SPECTシステムは中性子線とγ線が多量に存在する治療照射場内に設置されるため、有効な測定を行うためには、コリメータシステムの最適化が必要である。そこで、コリメータのパラメータを決めるに当たって、測定の統計誤差を考慮した最適指数を考案し、パラメータの最適化を行った。この結果をもとに組立式タングステンコリメータを作成し、計算と実測との比較を行った。予算の都合上、コリメータの一部しか製作できなかったが、計算値と実測値はほぼ一致しており、最適指数による最適化が妥当であったことを確認した。また、PG-SPECTに装備する検出器として、(1)中性子のダメージ、(2)検出効率、(3)エネルギー分解能、(4)バックグラウンド除去、(5)冷却の5項目について検討を行った結果、BGOシンチレーション検出器が最も有利であるという結論に達した。そこで、サイズの異なる3種類のBGOシンチレ...

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