研究者データベース

田中 創大(タナカ ソウダイ)
工学研究院 応用量子科学部門 量子生命工学
助教

基本情報

所属

  • 工学研究院 応用量子科学部門 量子生命工学

職名

  • 助教

学位

  • 博士(工学)(東京大学)

論文上での記載著者名

  • Sodai Tanaka

J-Global ID

研究キーワード

  • 陽子線飛程計算精度   Dual-Energy CT   陽子線CT   陽子線治療   医学物理   Computed Tomography   放射線治療   

研究分野

  • ライフサイエンス / 放射線科学
  • エネルギー / 量子ビーム科学
  • ライフサイエンス / 放射線科学

職歴

  • 2019年04月 - 現在 北海道大学 大学院工学研究院 助教
  • 2018年04月 - 2019年03月 北海道大学病院 放射線治療科 特任助教
  • 2016年08月 - 2016年12月 ドイツがん研究センター Guest Researcher

学歴

  • 2015年04月 - 2018年03月   東京大学   工学系研究科   原子力国際専攻 博士課程
  • 2013年04月 - 2015年03月   東京大学   工学系研究科   原子力国際専攻 修士課程
  •         - 2013年03月   東京大学   工学部   システム創成学科

所属学協会

  • 医学物理若手の会   日本放射線腫瘍学会   日本医学物理学会   

研究活動情報

論文

  • Sodai Tanaka, Yoshiyuki Noto, Satoru Utsunomiya, Takaaki Yoshimura, Taeko Matsuura, Masatoshi Saito
    Physics in Medicine & Biology 2020年08月11日 [査読有り][通常論文]
  • Koki Kasamatsu, Taeko Matsuura, Sodai Tanaka, Seishin Takao, Naoki Miyamoto, Jin-Min Nam, Hiroki Shirato, Shinichi Shimizu, Kikuo Umegaki
    Medical physics 2020年07月11日 [査読有り][通常論文]
     
    PURPOSE: The purpose of this study is to evaluate the sub-lethal damage (SLD) repair effect in prolonged proton irradiation using the biophysical model with various cell-specific parameters of (α/β)x and T1/2 (repair half time). At present, most of the model-based studies on protons have focused on acute radiation, neglecting the reduction in biological effectiveness due to SLD repair during the delivery of radiation. Nevertheless, the dose-rate dependency of biological effectiveness may become more important as advanced treatment techniques, such as hypofractionation and respiratory gating, come into clinical practice, as these techniques sometimes require long treatment times. Also, while previous research using the biophysical model revealed a large repair effect with a high physical dose, the dependence of the repair effect on cell-specific parameters has not been evaluated systematically. METHODS: Biological dose (relative biological effectiveness (RBE) × physical dose) calculation with repair included was carried out using the linear energy transfer (LET)-dependent linear-quadratic (LQ) model combined with the theory of dual radiation action (TDRA). First, we extended the dose protraction factor in the LQ model for the arbitrary number of different LET proton irradiations delivered sequentially with arbitrary time lags, referring to the TDRA. Using the LQ model, the decrease in biological dose due to SLD repair was systematically evaluated for spread-out Bragg peak (SOBP) irradiation in a water phantom with the possible ranges of both (α/β)x and repair parameters ((α/β)x = 1-15 Gy, T1/2 = 0-90 min). Then, to consider more realistic irradiation conditions, clinical cases of prostate, liver, and lung tumors were examined with the cell-specific parameters for each tumor obtained from the literature. Biological D99% and biological dose homogeneity coefficient (HC) were calculated for the clinical target volumes (CTVs), assuming dose-rate structures with a total irradiation time of 0-60 min. RESULTS: The differences in the cell-specific parameters resulted in considerable variation in the repair effect. The biological dose reduction found at the center of the SOBP with 30 min of continuous irradiation varied from 1.13% to 14.4% with a T1/2 range of 1-90 min when (α/β)x is fixed as 10 Gy. It varied from 2.3% to 6.8% with an (α/β)x range of 1-15 Gy for a fixed value of T1/2 = 30 min. The decrease in biological D99% per 10 min was 2.6, 1.2, and 3.0% for the prostate, liver, and lung tumor cases, respectively. The value of the biological D99% reduction was neither in the order of (α/β)x nor prescribed dose, but both comparably contributed to the repair effect. The variation of HC was within the range of 0.5% for all cases; therefore, the dose distribution was not distorted. CONCLUSION: The reduction in biological dose caused by the SLD repair largely depends on the cell-specific parameters in addition to the physical dose. The parameters should be considered carefully in the evaluation of the repair effect in prolonged proton irradiation.
  • Naoki Miyamoto, Kouhei Yokokawa, Seishin Takao, Taeko Matsuura, Sodai Tanaka, Shinichi Shimizu, Hiroki Shirato, Kikuo Umegaki
    Journal of applied clinical medical physics 2020年02月18日 [査読有り][通常論文]
     
    Spot-scanning particle therapy possesses advantages, such as high conformity to the target and efficient energy utilization compared with those of the passive scattering irradiation technique. However, this irradiation technique is sensitive to target motion. In the current clinical situation, some motion management techniques, such as respiratory-gated irradiation, which uses an external or internal surrogate, have been clinically applied. In surrogate-based gating, the size of the gating window is fixed during the treatment in the current treatment system. In this study, we propose a dynamic gating window technique, which optimizes the size of gating window for each spot by considering a possible dosimetric error. The effectiveness of the dynamic gating window technique was evaluated by simulating irradiation using a moving target in a water phantom. In dosimetric characteristics comparison, the dynamic gating window technique exhibited better performance in all evaluation volumes with different effective depths compared with that of the fixed gate approach. The variation of dosimetric characteristics according to the target depth was small in dynamic gate compared to fixed gate. These results suggest that the dynamic gating window technique can maintain an acceptable dose distribution regardless of the target depth. The overall gating efficiency of the dynamic gate was approximately equal or greater than that of the fixed gating window. In dynamic gate, as the target depth becomes shallower, the gating efficiency will be reduced, although dosimetric characteristics will be maintained regardless of the target depth. The results of this study suggest that the proposed gating technique may potentially improve the dose distribution. However, additional evaluations should be undertaken in the future to determine clinical applicability by assuming the specifications of the treatment system and clinical situation.
  • 高部美帆, 増田孝充, 有元誠, 片岡淳, 末岡晃紀, 丸橋拓也, 田中創大, 西尾禎治, 歳藤利行, 木村充宏, 稲庭拓
    Nuclear Instruments and Methods in Physics Research A 924 332 - 338 2019年04月 [査読有り][通常論文]
  • Yusuke Ochi, Akito Saito, Daisuke Kawahara, Tatsuhiko Suzuki, Masato Tsuneda, Sodai Tanaka, Teiji Nishio, Shuichi Ozawa, Yuji Murakami, Yasushi Nagata
    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) 58 59 - 65 2019年02月 [査読有り][通常論文]
     
    PURPOSE: The output of a linear accelerator (linac) is one of the most important quality assurance (QA) factors in radiotherapy. However, there is no quantitative rationale for frequency and tolerance. The purpose of this study is to develop a novel risk analysis of clinical reference dosimetry based on failure modes and effects analysis (FMEA). METHODS: Clinical reference dosimetry data and the daily output data of two linacs (Clinac iX and Clinac 6EX) at Hiroshima University Hospital were analyzed. The analysis involved the number of patients per year for five types of fractionations. Risk priority number (RPN) is defined as the product of occurrence (O), severity (S), and detectability (D) in standard FMEA. In addition, we introduced "severity due to output drifting" (mean output change per day) (S') and the number of patients per year for five types of fractionations (W). We calculated the RPN = O × S × D × S' × W and quantitatively evaluated the risk for clinical reference dosimetry. RESULTS: Fewer fractions and less output calibration frequency resulted in higher RPN. Since clinical reference dosimetry data has a drift effect, which is missing in human processes, it was essential to use S' in addition to standard FMEA. Moreover, the parameter W was important in evaluating interinstitutional QA for clinical reference dosimetry. The relative risk of Clinac 6EX to Clinac iX was different approximately by twofold. CONCLUSIONS: We developed a novel index that can quantitatively evaluate risk for clinical reference dosimetry of each facility and machines in common on the basis of FMEA.
  • Daisuke Kawahara, Shuichi Ozawa, Sodai Tanaka, Kazushi Yokomachi, Toru Higaki, Akito Saito, Kentaro Miki, Chikako Fujioka, Yoshimi Ohno, Yoshimi Ohno, Tomoki Kimura, Yuji Murakami, Yasushi Nagata
    The British journal of radiology 91 1090 20180396 - 20180396 2018年10月 [査読有り][通常論文]
     
    OBJECTIVE:: The purpose of the current study is to create a contrast medium extraction method using raw-data-based electron density (rED) and CT number from dual-energy CT (DECT) for automatic delineation of the contrast region. METHODS:: A CT-ED phantom containing tissue-equivalent inserts and an acrylic phantom with an iodinated contrast medium were scanned by DECT. The contrast medium extraction system was created using Python. The accuracy of the contrast medium extraction was evaluated by measuring the diameter in terms of the full width at half maximum (FWHM) and the ratio of the volume (ROV). RESULTS:: Mean-2SD CT numbers and the difference of the CT numbers (DCT) of the contrast medium at 0-130 mg ml-1 contrast medium concentration and the bone materials were more than -33 and -20 HU, respectively. In the correlation of rED and CT number, the gradient with the contrast medium phantom was greater than that with the CT-ED phantom. The accuracy of the contrast medium at 80 kV/135 kV and 100 kV/135 kV tube voltages. The gradient of the CT-ED and contrast medium phantoms were different. The gradient in the CT-ED phantom and the contrast medium was 0.0012 and 0.0003 at 80 kV/135 kV, and 0.0015 and 0.0005 at 100 kV/135 kV tube voltages, respectively. The ratio of the measured to the actual diameter in FWHM and ROV was 0.98-1.00 at 2-130 mg ml-1. At a tube voltage of 100 kV/135 kV. The ratio of the measured to the actual diameter in ROV was 0.66 and FWHM was 0.90 at 2 mg ml-1 contrast medium concentration. The ratio of the measured to the actual diameter in FWHM and ROV was 0.98-1.00 at 3-130 mg ml-1. CONCLUSION:: We created the contrast medium extraction method with rED and CT number images. The contrast medium extraction method could be used with DECT images at 80 kV/135 kV. The method is expected to only extract images from the region containing the contrast medium. ADVANCES IN KNOWLEDGE:: We created the contrast medium extraction method using raw-data-based electron density and CT number from DECT and it is expected to only extract information from the region containing the contrast medium.
  • Masato Tsuneda, Teiji Nishio, Akito Saito, Sodai Tanaka, Tatsuhiko Suzuki, Daisuke Kawahara, Keiichiro Matsushita, Aya Nishio, Shuichi Ozawa, Kumiko Karasawa, Yasushi Nagata
    Medical physics 45 6 2411 - 2424 2018年06月 [査読有り][通常論文]
     
    PURPOSE: High accuracy of the beam-irradiated position is required for high-precision radiation therapy such as stereotactic body radiation therapy (SBRT), volumetric modulated arc therapy (VMAT), and intensity modulated radiation therapy (IMRT). Users generally perform the verification of the mechanical and radiation isocenters using the star shot test and the Winston Lutz test that allow evaluation of the displacement at the isocenter. However, these methods are unable to evaluate directly and quantitatively the sagging angle that is caused by the weight of the gantry itself along the gantry rotation axis. In addition, the verification of the central axis of the irradiated beam that is not dependent at the isocenter is needed for the mechanical quality assurance of a nonisocentric irradiation technique. In this study, we have developed a prototype system for the verification of three-dimensional (3D) beam alignment and we have verified the system concept for 3D isocentricity. Our system allows detection of the central axis in 3D coordinates and evaluation of the irradiated oblique angle to the gantry rotation axis, i.e., the sagging angle. MATERIALS & METHODS: In order to measure the central axis of the irradiated beam in 3D coordinates, we constructed the prototype verification system consisting of a column-shaped plastic scintillator (CoPS), a truncated cone-shaped mirror (TCsM), and a cooled charged-coupled device (CCD) camera. This verification system was irradiated with 6-MV photon beams and the scintillation light was measured using the CCD camera. The central axis on the axial plane (two-dimensional (2D) central axis) was acquired from the integration of the scintillation light along the major axis of the CoPS, and the central axis in 3D coordinates (3D central axis) was acquired from two curve-shaped profiles which were reflected by the TCsM. We verified the calculation accuracy of the gantry rotation axis, θz . Additionally, we calculated the 3D central axis and the sagging angle at each gantry angle. RESULTS: We acquired the measurement images composed of the 2D central axis and the two curve-shaped profiles. The relationship between the irradiated and measured angles with respect to the gantry rotation axis had good linearity. The mean and standard deviation of the difference between the irradiated and measured angles were 0.012 and 0.078 degrees, respectively. The size of the 2D and 3D radiation isocenters were 0.470 and 0.652 mm on the axial plane and in 3D coordinates, respectively. The sagging angles were -0.31, 0.39, and 0.38 degrees at the gantry angles of 0, 180, and 180E degrees, respectively. CONCLUSION: We developed a novel verification system, designated as the "kompeito shot test system," to verify the 3D beam alignment. This system concept works for both verification of the 3D isocentricity and the direct evaluation of the sagging angle. Next, we want to improve the aspects of this system, such as the shape and the type of scintillator, to increase the system accuracy and nonisocentric beam alignment performance.
  • Daisuke Kawahara, Shuichi Ozawa, Akito Saito, Tomoki Kimura, Tatsuhiko Suzuki, Masato Tsuneda, Sodai Tanaka, Takeo Nakashima, Yoshimi Ohno, Yuji Murakami, Yasushi Nagata
    Journal of applied clinical medical physics 19 2 211 - 217 2018年03月 [査読有り][通常論文]
     
    PURPOSE: Lipiodol, which was used in transcatheter arterial chemoembolization before liver stereotactic body radiation therapy (SBRT), remains in SBRT. Previous we reported the dose enhancement in Lipiodol using 10 MV (10×) FFF beam. In this study, we compared the dose enhancement in Lipiodol and evaluated the probability of electron generation (PEG) for the dose enhancement using flattening filter (FF) and flattening filter free (FFF) beams. METHODS: FF and FFF for 6 MV (6×) and 10× beams were delivered by TrueBeam. The dose enhancement factor (DEF), energy spectrum, and PEG was calculated using Monte Carlo (MC) code BEAMnrc and heavy ion transport code system (PHITS). RESULTS: DEFs for FF and FFF 6× beams were 7.0% and 17.0% at the center of Lipiodol (depth, 6.5 cm). DEFs for FF and FFF 10× beams were 8.2% and 10.5% at the center of Lipiodol. Spectral analysis revealed that the FFF beams contained more low-energy (0-0.3 MeV) electrons than the FF beams, and the FF beams contained more high-energy (>0.3 MeV) electrons than the FFF beams in Lipiodol. The difference between FFF and FF beam DEFs was larger for 6× than for 10×. This occurred because the 10× beams contained more high-energy electrons. The PEGs for photoelectric absorption and Compton scattering for the FFF beams were higher than those for the FF beams. The PEG for the photoelectric absorption was higher than that for Compton scattering. CONCLUSIONS: FFF beam contained more low-energy photons and it contributed to the dose enhancement. Energy spectra and PEGs are useful for analyzing the mechanisms of dose enhancement.
  • Daisuke Kawahara, Shuichi Ozawa, Kazushi Yokomachi, Sodai Tanaka, Toru Higaki, Chikako Fujioka, Tatsuhiko Suzuki, Masato Tsuneda, Takeo Nakashima, Yoshimi Ohno, Yasushi Nagata
    The British journal of radiology 91 1082 20170524 - 20170524 2018年02月 [査読有り][通常論文]
     
    OBJECTIVE: To evaluate the accuracy of raw-data-based effective atomic number (Zeff) values and monochromatic CT numbers for contrast material of varying iodine concentrations, obtained using dual-energy CT. METHODS: We used a tissue characterization phantom and varying concentrations of iodinated contrast medium. A comparison between the theoretical values of Zeff and that provided by the manufacturer was performed. The measured and theoretical monochromatic CT numbers at 40-130 keV were compared. RESULTS: The average difference between the Zeff values of lung (inhale) inserts in the tissue characterization phantom was 81.3% and the average Zeff difference was within 8.4%. The average difference between the Zeff values of the varying concentrations of iodinated contrast medium was within 11.2%. For the varying concentrations of iodinated contrast medium, the differences between the measured and theoretical monochromatic CT values increased with decreasing monochromatic energy. The Zeff and monochromatic CT numbers in the tissue characterization phantom were reasonably accurate. CONCLUSION: The accuracy of the raw-data-based Zeff values was higher than that of image-based Zeff values in the tissue-equivalent phantom. The accuracy of Zeff values in the contrast medium was in good agreement within the maximum SD found in the iodine concentration range of clinical dynamic CT imaging. Moreover, the optimum monochromatic energy for human tissue and iodinated contrast medium was found to be 70 keV. Advances in knowledge: The accuracy of the Zeff values and monochromatic CT numbers of the contrast medium created by raw-data-based, dual-energy CT could be sufficient in clinical conditions.
  • Sodai Tanaka, Teiji Nishio, Masato Tsuneda, Keiichiro Matsushita, Shigeto Kabuki, Mitsuru Uesaka
    Physics in Medicine and Biology 63 3 035030  2018年02月01日 [査読有り][通常論文]
     
    Range uncertainty is among the most formidable challenges associated with the treatment planning of proton therapy. Proton imaging, which includes proton radiography and proton computed tomography (pCT), is a useful verification tool. We have developed a pCT detection system that uses a thick bismuth germanium oxide (BGO) scintillator and a CCD camera. The current method is based on a previous detection system that used a plastic scintillator, and implements improved image processing techniques. In the new system, the scintillation light intensity is integrated along the proton beam path by the BGO scintillator, and acquired as a two-dimensional distribution with the CCD camera. The range of a penetrating proton is derived from the integrated light intensity using a light-to-range conversion table, and a pCT image can be reconstructed. The proton range in the BGO scintillator is shorter than in the plastic scintillator, so errors due to extended proton ranges can be reduced. To demonstrate the feasibility of the pCT system, an experiment was performed using a 70 MeV proton beam created by the AVF930 cyclotron at the National Institute of Radiological Sciences. The accuracy of the light-to-range conversion table, which is susceptible to errors due to its spatial dependence, was investigated, and the errors in the acquired pixel values were less than 0.5 mm. Images of various materials were acquired, and the pixel-value errors were within 3.1%, which represents an improvement over previous results. We also obtained a pCT image of an edible chicken piece, the first of its kind for a biological material, and internal structures approximately one millimeter in size were clearly observed. This pCT imaging system is fast and simple, and based on these findings, we anticipate that we can acquire 200 MeV pCT images using the BGO scintillator system.
  • Daisuke Kawahara, Hisashi Nakano, Shuichi Ozawa, Akito Saito, Tomoki Kimura, Tatsuhiko Suzuki, Masato Tsuneda, Sodai Tanaka, Yoshimi Ohno, Yuji Murakami, Yasushi Nagata
    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) 46 89 - 95 2018年02月 [査読有り][通常論文]
     
    OBJECTIVES: We examine the contrast agent Lipiodol effect on the relative biological effectiveness (RBE) values for flattening filter free (FFF) and flattening filter (FF) beams of 6 MV-Xray (6 MVX) and 10 MVX. METHODS: Lipiodol was placed at 5 cm depth in water. According to the microdosimetric kinetic model, the RBE values for killing the human liver hepatocellular cells were calculated from dose and lineal energy (yd(y)) from Monte Carlo simulations. RBE200kVX and RBECo were defined as the ratios of dose using reference radiation (200 kVX, Co-ɤ) to the dose of test radiation (FFF and FF beams for 6 MV and 10 MV) to produce the same biological effects. The dose enhancement RBE (RBEDE) was defined as the ratios of a dose without Lipiodol to with Lipiodol using to produce the same biological effects. The dose needed to achieve 10% (D10%) and 1% cell survival (D1%) was evaluated by cell surviving fraction (SF) formula. RESULTS: The deviation of mean y‾D values with and without Lipiodol were 3.9-4.8% for 6 MVX and 3.5-3.6% for 10 MVX. The RBE200kVX and RBECo with Lipiodol were larger than that without Lipiodol. The RBEDE was larger for FFF beam than for FF beam. The deviation of RBEDE for FFF and FF beams of 6 MVX was larger than that of 10 MVX. CONCLUSION: The presence of Lipiodol seemed to locally increase the absorbed dose and to also cause an enhancement of the relative biological effectiveness.
  • Daisuke Kawahara, Shuichi Ozawa, Akito Saito, Tomoki Kimura, Tatsuhiko Suzuki, Masato Tsuneda, Sodai Tanaka, Kazunari Hioki, Takeo Nakashima, Yoshimi Ohno, Yuji Murakami, Yasushi Nagata
    Reports of Practical Oncology and Radiotherapy 23 1 50 - 56 2018年01月01日 [査読有り][通常論文]
     
    Aim Lipiodol was used for stereotactic body radiotherapy combining trans arterial chemoembolization. Lipiodol used for tumour seeking in trans arterial chemoembolization remains in stereotactic body radiation therapy. In our previous study, we reported the dose enhancement effect in Lipiodol with 10× flattening-filter-free (FFF). The objective of our study was to evaluate the dose enhancement and energy spectrum of photons and electrons due to the Lipiodol depth with flattened (FF) and FFF beams. Methods FF and FFF for 6 MV beams from TrueBeam were used in this study. The Lipiodol (3 × 3 × 3 cm3) was located at depths of 1, 3, 5, 10, 20, and 30 cm in water. The dose enhancement factor (DEF) and the energy fluence were obtained by Monte Carlo calculations of the particle and heavy ion transport code system (PHITS). Results The DEFs at the centre of Lipiodol with the FF beam were 6.8, 7.3, 7.6, 7.2, 6.1, and 5.7% and those with the FFF beam were 20.6, 22.0, 21.9, 20.0, 12.3, and 12.1% at depths of 1, 3, 5, 10, 20, and 30 cm, respectively, where Lipiodol was located in water. Moreover, spectrum results showed that more low-energy photons and electrons were present at shallow depth where Lipiodol was located in water. The variation in the low-energy spectrum due to the depth of the Lipiodol position was more explicit with the FFF beam than that with the FF beam. Conclusions The current study revealed variations in the DEF and energy spectrum due to the depth of the Lipiodol position with the FF and FFF beams. Although the FF beam could reduce the effect of energy dependence due to the depth of the Lipiodol position, the dose enhancement was overall small. To cause a large dose enhancement, the FFF beam with the distance of the patient surface to Lipiodol within 10 cm should be used.
  • Daisuke Kawahara, Shuichi Ozawa, Takeo Nakashima, Tatsuhiko Suzuki, Masato Tsuneda, Sodai Tanaka, Yoshimi Ohno, Yuji Murakami, Yasushi Nagata
    PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS 32 12 1628 - 1633 2016年12月 [査読有り][通常論文]
     
    Purpose: Nowadays, patient positioning and target localization can be verified by using kilovolt cone beam computed tomography (kV-CBCT). There have been various studies on the absorbed doses and image qualities of different kV-CBCT systems. However, the Varian TrueBeam CBCT (TB CBCT) system has not been investigated so far. We assess the image quality and absorbed dose of TB CBCT through comparison with those of on-board imager (OBI) CBCT. Methods: The image quality was evaluated using two phantoms. A CATPHAN phantom measured the image quality parameters of the American Association of Physicists in Medicine Task Group 142 (AAPM TG-142) report. These factors are the pixel value stability and accuracy, noise, high-contrast resolution, low-contrast resolution, and image uniformity. A H2SO4 phantom was used to evaluate the image uniformity over a larger region than the CATPHAN phantom. In evaluating the absorbed dose, the radial dose profile and the patient organ doses at the prostate and rectum levels were evaluated. Results: The image quality parameters of AAPM TG-142 using TB CBCT are equal to or greater than those of OBI CBCT. In particular, the contrast-to-noise ratio with TB CBCT is 2.5 times higher than that with OBI CBCT. For the test of a large field uniformity, the maximum difference in the Hounsfield unit (HU) values between the centre and peripheral regions is within 30 HU with TB CBCT and 283 HU with OBI CBCT. The maximum absorbed dose with TB CBCT is decreased by 60%. Conclusions: We find that the image quality improved and the absorbed dose decreased with TB CBCT in comparison to those with OBI CBCT. Its image uniformity is also superior over a larger scanning range. (C) 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
  • 西尾禎治, 田中創大, 松下慶一郎, 恒田雅人, 株木重人, 前田宗利, 伊東富由美, 久米恭
    若狭湾エネルギー研究センター研究年報 18 42‐43  2016年10月 [査読無し][通常論文]
  • Sodai Tanaka, Teiji Nishio, Keiichiro Matsushita, Masato Tsuneda, Shigeto Kabuki, Mitsuru Uesaka
    PHYSICS IN MEDICINE AND BIOLOGY 61 11 4156 - 4167 2016年06月 [査読有り][通常論文]
     
    A proton computed tomography (pCT) imaging system was constructed for evaluation of the error of an x-ray CT (xCT)-to-WEL (water-equivalent length) conversion in treatment planning for proton therapy. In this system, the scintillation light integrated along the beam direction is obtained by photography using the CCD camera, which enables fast and easy data acquisition. The light intensity is converted to the range of the proton beam using a light-to-range conversion table made beforehand, and a pCT image is reconstructed. An experiment for demonstration of the pCT system was performed using a 70 MeV proton beam provided by the AVF930 cyclotron at the National Institute of Radiological Sciences. Three-dimensional pCT images were reconstructed from the experimental data. A thin structure of approximately 1 mm was clearly observed, with spatial resolution of pCT images at the same level as that of xCT images. The pCT images of various substances were reconstructed to evaluate the pixel value of pCT images. The image quality was investigated with regard to deterioration including multiple Coulomb scattering.
  • M. Uesaka, K. Demachi, T. Fujiwara, K. Dobashi, H. Fujisawa, R. B. Chhatkuli, A. Tsuda, S. Tanaka, Y. Matsumura, S. Otsuki, J. Kusano, M. Yamamoto, N. Nakamura, E. Tanabe, K. Koyama, M. Yoshida, R. Fujimori, A. Yasui
    IOP Conference Series: Materials Science and Engineering 79 1 012015  2015年06月10日 [査読有り][通常論文]
     
    We are developing compact electron linear accelerators (hereafter linac) with high RF (Radio Frequency) frequency (9.3 GHz, wavelength 32.3 mm) of X-band and applying to medicine and non-destructive testing. Especially, potable 950 keV and 3.95 MeV linac X-ray sources have been developed for on-site transmission testing at several industrial plants and civil infrastructures including bridges. 6 MeV linac have been made for pinpoint X-ray dynamic tracking cancer therapy. The length of the accelerating tube is ∼600 mm. The electron beam size at the X-ray target is less than 1 mm and X-ray spot size at the cancer is less than 3 mm. Several hardware and software are under construction for dynamic tracking therapy for moving lung cancer. Moreover, as an ultimate compact linac, we are designing and manufacturing a laser dielectric linac of ∼1 MeV with Yr fiber laser (283 THz, wavelength 1.06 pm). Since the wavelength is 1.06 μm, the length of one accelerating strcture is tens pm and the electron beam size is in sub-micro meter. Since the sizes of cell and nuclear are about 10 and 1 μm, respectively, we plan to use this "On-chip" linac for radiation-induced DNA damage/repair analysis. We are thinking a system where DNA in a nucleus of cell is hit by ∼1 μm electron or X-ray beam and observe its repair by proteins and enzymes in live cells in-situ.
  • T. Fujiwara, S. Tanaka, Y. Mitsuya, H. Takahashi, K. Tagi, J. Kusano, E. Tanabe, M. Yamamoto, N. Nakamura, K. Dobashi, H. Tomita, M. Uesaka
    JOURNAL OF INSTRUMENTATION 8 C12020  2013年12月 [査読有り][通常論文]
     
    We recently developed glass gas electron multipliers (G-GEMs) with an entirely new process using photo-etchable glass. The photo-etchable glass used for the substrate is called PEG3 (Hoya Corporation). Taking advantage of low outgassing material, we have envisioned a medical application of G-GEMs. A two-dimensional position-sensitive dosimetry system based on a scintillating gas detector is being developed for real-time dose distribution monitoring in X-ray radiation therapy. The dosimetry system consists of a chamber filled with an Ar/CF4 scintillating gas mixture, inside of which G-GEM structures are mounted. Photons produced by the excited Ar/CF4 gas molecules during the gas multiplication in the GEM holes are detected by a mirror-lens-CCD-camera system. We found that the intensity distribution of the measured light spot is proportional to the 2D dose distribution. In this work, we report on the first results from a scintillating G-GEM detector for a position-sensitive X-ray beam dosimeter.

講演・口頭発表等

  • シンチレータとCCDカメラを用いた線量積算型陽子線CT画像取得法の研究  [通常講演]
    田中創大, 西尾禎治, 恒田雅人, 高部美帆, 増田孝充, 株木重人, 久米恭, 長谷川崇, 上坂充
    日本放射線腫瘍学会第30回学術大会 2017年11月 ポスター発表
  • Improvement of proton CT imaging system using BGO scintillator and CCD camera  [通常講演]
    S. Tanaka, T. Nishio, K. Matsushita, M. Tsuneda, S. Kabuki, M. Uesaka
    European Congress of Radiology 2017 2017年03月 ポスター発表
  • Development of proton CT imaging system using thick scintillator and CCD camera  [通常講演]
    S. Tanaka, T. Nishio, K. Matsushita, M. Tsuneda, S. Kabuki, M. Uesaka
    58th Annual Meeting of the American Association of Physicists in Medicine 2016年07月 口頭発表(一般)
  • Development of proton CT imaging system  [通常講演]
    S. Tanaka, T. Nishio, K. Matsushita, M. Tsuneda, S. Kabuki, M. Uesaka
    European Congress of Radiology 2016 2016年03月 ポスター発表
  • 陽子線CT画像取得法の確立  [通常講演]
    田中創大, 西尾禎治, 松下慶一郎, 恒田雅人, 株木重人, 上坂充
    日本放射線腫瘍学会第29回高精度放射線外部照射部会学術大会 2016年02月 ポスター発表
  • 陽子線CT画像取得法の研究  [通常講演]
    田中創大
    Geant4研究会医学応用研究会 2015年12月 口頭発表(一般)
  • Improvement of proton CT imaging system  [通常講演]
    S. Tanaka, T. Nishio, K. Matsushita, M. Tsuneda, S. Kabuki, A. Sugiura, M. Uesaka
    第110回日本医学物理学会学術大会 2015年09月 口頭発表(一般)
  • Study on proton CT for evaluation of water equivalent length factor  [通常講演]
    S. Tanaka, T. Nishio, K. Matsushita, M. Tsuneda, Y. Aono, S. Kabuki, A. Sugiura, M. Uesaka
    15th International Congress of Radiation Research 2015年05月 ポスター発表
  • 陽子線治療における体内中飛程計算精度向上のための陽子線CT画像取得法の研究  [通常講演]
    田中創大, 西尾禎治, 松下慶一郎, 中村哲志, 恒田雅人, 青野裕樹, 余語克紀, 株木重人, 上坂充
    日本放射線腫瘍学会第27回学術大会 2014年12月 口頭発表(一般)
  • Development of proton CT imaging system for evaluation of proton range calculation accuracy  [通常講演]
    S. Tanaka, T. Nishio, K. Matsushita, M. Tsuneda, Y. Aono, S. Kabuki, A. Sugiura, M. Uesaka
    Fourth Joint Meeting of the Nuclear Physics Divisions of the American Physical Society and The Physical Society of Japan 2014年10月 口頭発表(一般)
  • 陽子線CT画像取得法の研究  [通常講演]
    田中創大, 西尾禎治, 松下慶一郎, 中村哲志, 恒田雅人, 青野裕樹, 余語克紀, 株木重人, 上坂充
    第107回日本医学物理学会学術大会 2014年04月 口頭発表(一般)
  • シンチレーションガスとGlassGEMを用いたX線がん治療機用リアルタイムビームモニタリングシステムの開発  [通常講演]
    田中創大, 田儀和浩, 藤原健, 高橋浩之, 上坂充, 草野譲一, 中村直樹, 山本昌志, 菅原浩一, 田辺英二
    日本原子力学会2013年春の年会 2013年03月 口頭発表(一般)
  • シンチレーションガスとGlassGEMを用いたX線がん治療用リアルタイムビームモニタリングシステムの開発  [通常講演]
    田中創大, 田儀和浩, 藤原健, 高橋浩之, 上坂充, 草野譲一, 中村直樹, 山本昌志, 菅原浩一, 田辺英二
    日本原子力学会関東・甲信支部第6回学生研究発表会 2013年03月 口頭発表(一般)

その他活動・業績

  • 西尾 禎治, 松下 慶一郎, 関根 雅晃, 中村 哲志, 田中 創大, 宮武 彩 日本放射線技術學會雜誌 69 (11) 1297 -1305 2013年11月20日 [査読無し][通常論文]

受賞

  • 2018年03月 東京大学 工学系研究科長賞
     
    受賞者: 田中 創大
  • 2013年03月 日本機械学会 畠山賞
     
    受賞者: 田中 創大

共同研究・競争的資金等の研究課題

  • 陽子線CT搭載型ヘリウム・陽子線混合治療装置と免疫賦活照射法の研究開発
    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 -2024年03月 
    代表者 : 白土 博樹, 宮本 直樹, 平田 雄一, 田中 創大, 高尾 聖心, 梅垣 菊男, 茶本 健司, 清水 伸一, Nam JinMin, 小野寺 康仁, 松浦 妙子
  • スキャニングビーム陽子線CT画像取得法の研究開発
    日本学術振興会:科学研究費助成事業 若手研究
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 田中 創大
  • 陽子線CT画像取得法の研究
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2017年04月 -2019年03月 
    代表者 : 田中 創大
     
    現在、陽子線治療の治療計画では患者のX線CT画像を基に陽子線の線量計算が行われているが、陽子線飛程計算の不確定性は3%と報告されている。治療で用いる30 cmの飛程の陽子線の場合で9 mmにも及び、ブラックピークの活用による線量集中性が良さである陽子線治療の大きな問題点となっている。その解決手法の1つとして陽子線CT画像の利用があげられ、陽子線と物質の相互作用量をそのままイメージングすることで、前述の3%の不確定性を大きく減少させることができる。陽子線CT画像取得法が確立していない現状に対して、本研究では臨床利用可能な陽子線CT画像取得法の研究開発を行った。検出システムは主に厚いシンチレータとCCDカメラから構成される。陽子線イメージングでは被写体透過前後のエネルギーの差を投影データとして取得するが、本システムでは厚いシンチレータで陽子線を全て停止させ、その発光のビーム方向積算値をCCDカメラで取得することで2次元陽子線エネルギー分布を取得した。また被写体を回転させることにより360度方向からのデータを取得し、再構成することで陽子線CT画像を得た。この手法はシンプルな検出システムでかつ短時間で測定できることが長所である。 シンチレータの種類や実験パラメータなどのハード面と画像処理・再構成手法のソフト面の両面での改善を行い、臨床に用いられている陽子線ビームを用いて検出システムの実証実験を実施することができた。その結果、実験的に本システムで取得できる陽子線CT画像の精度は臨床利用レベルにまで到達した。

大学運営

その他

  • 2016年06月 - 2016年06月  Proton CT could ease treatment planning 
    Medical Physics Web http://medicalphysicsweb.org/cws/article/research/65359


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