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Last Updated :2024/07/25

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Master

Affiliation (Master)

  • Hokkaido University Hospital　Central Clinical Facilities

Affiliation (Master)

  • Hokkaido University Hospital　Central Clinical Facilities

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Profile and Settings

Profile and Settings

  • Name (Japanese)

    Tamura

  • Name (Kana)

    Masaya

  • Name

    201501015810505617

Achievement

Research Areas

  • Energy / Quantum beam science
  • Life sciences / Radiology

Published Papers

  • Masaya Tamura, Hideyuki Sakurai, Masashi Mizumoto, Satoshi Kamizawa, Shigeyuki Murayama, Haruo Yamashita, Seishin Takao, Ryusuke Suzuki, Hiroki Shirato, Yoichi M. Ito
    JOURNAL OF RADIATION RESEARCH 58 (3) 363 - 371 0449-3060 2017/05 [Refereed][Not invited]
     
    To investigate the amount that radiation-induced secondary cancer would be reduced by using proton beam therapy (PBT) in place of intensity-modulated X-ray therapy (IMXT) in pediatric patients, we analyzed lifetime attributable risk (LAR) as an in silico surrogate marker of the secondary cancer after these treatments. From 242 pediatric patients with cancers who were treated with PBT, 26 patients were selected by random sampling after stratification into four categories: (i) brain, head and neck, (ii) thoracic, (iii) abdominal, and (iv) whole craniospinal (WCNS) irradiation. IMXT was replanned using the same computed tomography and region of interest. Using the dose-volume histograms (DVHs) of PBT and IMXT, the LARs of Schneider et al. were calculated for the same patient. All the published dose-response models were tested for the organs at risk. Calculation of the LARs of PBT and IMXT based on the DVHs was feasible for all patients. The means +/- standard deviations of the cumulative LAR difference between PBT and IMXT for the four categories were (i) 1.02 +/- 0.52% (n = 7, P = 0.0021), (ii) 23.3 +/- 17.2% (n = 8, P = 0.0065), (iii) 16.6 +/- 19.9% (n = 8, P = 0.0497) and (iv) 50.0 +/- 21.1% (n = 3, P = 0.0274), respectively (one tailed t-test). The numbers needed to treat (NNT) were (i) 98.0, (ii) 4.3, (iii) 6.0 and (iv) 2.0 for WCNS, respectively. In pediatric patients who had undergone PBT, the LAR of PBT was significantly lower than the LAR of IMXT estimated by in silico modeling. Although a validation study is required, it is suggested that the LAR would be useful as an in silico surrogate marker of secondary cancer induced by different radiotherapy techniques.
  • Shintani N, Monzen H, Tamura M, Asai Y, Shimomura K, Matsumoto K, Okumura M, Nishimura Y
    Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 一般社団法人 日本医学物理学会 35 (4) 282 - 291 1345-5354 2016 [Refereed][Not invited]
     
    The purpose of this study is to evaluate the mechanical accuracy of a respiratory-gated radiation system that combines the Linear Indicator-equipped Abches respiration-monitoring device and the Varian Real-time Position Management system (LI-RPM system). This combined configuration, implemented for the first time in Japan, was compared with the stand-alone Varian RPM system (RPM system). The delay times, dose profiles, and output waveforms of the LI-RPM and RPM systems were evaluated using a self-produced dynamic phantom. The delay times for the LI-RPM and RPM systems were both 0.1 s for 4 s and 8 s test periods. The corresponding output waveform correlation factors (R2) for the 4 s and 8 s test periods were 0.9981 and 0.9975, respectively. No difference was observed in the dose profiles of the two systems. Thus, the present results indicate that the proposed LI-RPM combined respiratory-gated radiation system has similar properties to the RPM system. However, it offers several advantages in terms of its versatility, including its alignment assistance capabilities for non-coplanar treatments.
  • Yabuta K, Monzen H, Tamura M, Tsuruta T, Itou T, Nohtomi A, Nishimura Y
    Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics 34 (3) 139 - 148 1345-5354 2014 [Refereed][Not invited]
  • Izumi Tachibana, Yasumasa Nishimura, Toru Shibata, Shuichi Kanamori, Kiyoshi Nakamatsu, Ryuta Koike, Tatsuyuki Nishikawa, Kazuki Ishikawa, Masaya Tamura, Makoto Hosono
    Journal of Radiation Research 54 (6) 1078 - 1084 0449-3060 2013/11 [Refereed][Not invited]
     
    To visualize intratumoral hypoxic areas and their reoxygenation before and during fractionated radiation therapy (RT), 18F-fluoromisonidazole positron emission tomography and computed tomography (F-MISOPET/CT) were performed. A total of 10 patients, consisting of four with head and neck cancers, four with gastrointestinal cancers, one with lung cancer, and one with uterine cancer, were included. F-MISO PET/CT was performed twice, before RT and during fractionated RT of approximately 20 Gy/10 fractions, for eight of the 10 patients. F-MISO maximum standardized uptake values (SUVmax) of normal muscles and tumors were measured. The tumor-to-muscle (T/M) ratios of F-MISO SUVmax were also calculated. Mean SUVmax ± standard deviation (SD) of normal muscles was 1.25 ± 0.17, and SUVmax above the mean + 2 SD (=1.60 SUV) was regarded as a hypoxic area. Nine of the 10 tumors had an F-MISO SUVmax of =1.60. All eight tumors examined twice showed a decrease in the SUVmax, T/M ratio, or percentage of hypoxic volume (F-MISO =1.60) at approximately 20 Gy, indicating reoxygenation. In conclusion, accumulation of F-MISO of =1.60 SUV was regarded as an intratumoral hypoxic area in our F-MISO PET/CT system. Most human tumors (90%) in this small series had hypoxic areas before RT, although hypoxic volume was minimal (0.0-0.3%) for four of the 10 tumors. In addition, reoxygenation was observed in most tumors at two weeks of fractionated RT. © The Author 2013. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Therapeutic Radiology and Oncology.
  • Kenji Matsumoto, Masahiko Okumura, Yoshiyuki Asai, Kouhei Shimomura, Masaya Tamura, Yasumasa Nishimura
    Radiological Physics and Technology 6 (1) 210 - 218 1865-0333 2013/01 [Refereed][Not invited]
     
    Dosimetric properties of an amorphous silicon electronic portal imaging device (EPID) for verification of intensity-modulated radiation therapy (IMRT) were investigated as a replacement for conventional verification tools. The portal dosimetry system of Varian's EPID (aS1000) has an integrated image mode for portal dosimetry (PD). The source-to-imager distance was 105 cm, and there were no extra buildup materials on the surface of the EPID in this study. Several dosimetric properties were examined. For clinical dosimetry, the dose distributions of dynamic IMRT beams for prostate cancer (19 patients, 97 beams) were measured by EPID and compared with the results of ionization chamber (IC) measurements. In addition, pretreatment measurements for prostate IMRT (50 patients, 309 beams) were performed by EPID and were evaluated by the gamma method (criterion: 3 mm/3 %). The signal-to-monitor unit ratio of PD showed dose dependence, indicating ghosting effects. Tongue-and-groove effects were observed as a result of the dose difference in the measured EPID images. The results of PD for clinical IMRT beams were in good agreement with the predicted dose image with average values of 1.37 and 0.25 for γ max and γ ave, respectively. The point doses of PD were slightly, but significantly, higher than the results of IC measurements (p < 0.05 paired t test). However, this small difference seems clinically acceptable. This portal dosimetry system is useful as a rapid and convenient verification tool for dynamic IMRT. © 2012 Japanese Society of Radiological Technology and Japan Society of Medical Physics.
  • Tamaki Nishi, Yasumasa Nishimura, Toru Shibata, Masaya Tamura, Naohiro Nishigaito, Masahiko Okumura
    Radiotherapy and Oncology 106 (1) 85 - 89 0167-8140 2013/01 [Refereed][Not invited]
     
    Purpose: The aim of this study was to show the benefit of a two-step intensity modulated radiotherapy (IMRT) method by examining geometric and dosimetric changes. Material and Methods: Twenty patients with pharyngeal cancers treated with two-step IMRT combined with chemotherapy were included. Treatment-planning CT was done twice before IMRT (CT-1) and at the third or fourth week of IMRT for boost IMRT (CT-2). Transferred plans recalculated initial plan on CT-2 were compared with the initial plans on CT-1. Dose parameters were calculated for a total dose of 70 Gy for each plan. Results: The volumes of primary tumors and parotid glands on CT-2 regressed significantly. Parotid glands shifted medially an average of 4.2 mm on CT-2. The mean doses of the parotid glands in the initial and transferred plans were 25.2 Gy and 30.5 Gy, respectively. D2 (dose to 2% of the volume) doses of the spinal cord were 37.1 Gy and 39.2 Gy per 70 Gy, respectively. Of 15 patients in whom xerostomia scores could be evaluated 1-2 years after IMRT, no patient complained of grade 2 or more xerostomia. Conclusions: This two-step IMRT method as an adaptive RT scheme could adapt to changes in body contour, target volumes and risk organs during IMRT. © 2013 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology.
  • Yasumasa Nishimura, Toru Shibata, Kiyoshi Nakamatsu, Shuichi Kanamori, Ryuta Koike, Mitsuru Okubo, Tatsuyuki Nishikawa, Izumi Tachibana, Masaya Tamura, Masahiko Okumura
    JAPANESE JOURNAL OF CLINICAL ONCOLOGY 40 (2) 130 - 138 0368-2811 2010/02 [Refereed][Not invited]
     
    The aim of this study was to analyze the clinical results of our adaptive radiation therapy scheme of a two-step intensity-modulated radiotherapy (IMRT) method for nasopharyngeal cancer (NPC) at Kinki University Hospital. Between 2000 and 2007, 35 patients with Stage I-IVB NPC treated by IMRT were included. For all patients, treatment-planning computed tomography was done twice before and during IMRT to a total dose of 60-70 Gy/28-35 fractions (median 68 Gy). Chemotherapy (cisplatin 80 mg/m(2)/3 weeks x 1-3 courses) was given concurrently with IMRT for 31 patients. The 3- and 5-year overall survival rates for the 31 patients treated with concurrent chemotherapy were 88% and 83%, respectively. The 3- and 5-year loco-regional control rates for the 31 patients were 93% and 87%, respectively. Planning target volume delineation for the primary site or involved nodes was insufficient for three early cases, resulting in marginal recurrence in the three patients (9%). Except for one patient with early death, xerostomia scores at 1-2 years were: Grade 0, 11; Grade 1, 17; Grade 2, 5; Grade 3, 1. Excellent overall survival and loco-regional control rates were obtained by a two-step IMRT method with concurrent chemotherapy for NPC, although marginal recurrence was noted in some early cases.
  • T Sawamura, JH Kaneko, M Abe, M Tamura, Murai, I, A Homma, F Fujita, S Tsuda
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 505 (1-2) 29 - 32 0168-9002 2003/06 [Not refereed][Not invited]
     
    The response of superheated drop detectors or bubble detectors (BDs) was measured for quasi-monoenergetic neutron beams in the 40-75 MeV range and the effects of a lead-converter enclosing the detector introduced to extend the response to the high-energy region were discussed. The experiments were performed in the quasi-monoenergetic neutron beam field at the AVF cyclotron facility, TAKASAKI Ion Accelerator for Advanced Radiation Application (TIARA) of Japan Atomic Energy Research Institute(JAERI). Monte Carlo calculations by MCNPX code were carried out to estimate the lead-converter effect on neutron spectra in a detector exposed to 40-75 MeV quasi-monoenergetic source neutrons. The calculations indicated an increase in the energy ranges of the neutrons of 0.1-10 MeV and this can be expected to increase the number of bubbles produced in the detector. Experimental results showed that the sensitivity was lowered to about a half the nominal sensitivity and that a 3 cm thick lead-converter could compensate for the sensitivity decrease in the experimental energy region. (C) 2003 Elsevier Science B.V. All rights reserved.
  • M Tamura, T Akimoto, Y Aoki, J Ikeda, K Sato, F Fujita, A Homma, T Sawamura, M Narita
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 484 (1-3) 642 - 649 0168-9002 2002/05 [Not refereed][Not invited]
     
    When electrons at relativistic velocities pass through a crystal plate, such as silicon, photons are emitted around the Bragg angle for X-ray diffraction. This phenomenon is called parametric X-ray radiation (PXR). The monochromaticity and directivity of PXR are adequate and the energy can be changed continuously by rotating the crystal. This study measured the mass attenuation coefficient around the K-shell absorption edge of Nb, Zr and Mo as a PXR application of monochromatic hard X-ray radiation sources. (C) 2002 Elsevier Science B.V. All rights reserved.
  • T Akimoto, M Tamura, J Ikeda, Y Aoki, F Fujita, K Sato, A Honma, T Sawamura, M Narita, K Imai
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 459 (1-2) 78 - 86 0168-9002 2001/02 [Not refereed][Not invited]
     
    Parametric X-ray radiation (PXR) at energies from 15 to 30 keV was produced by a 45 MeV electron linear accelerator (LINAC) using a silicon (Si) single crystal. The appropriate conditions for generation of good monochromatic hard X-cay fields by PXR were obtained with the LINAC by theoretical calculations and experiments. The PXR intensity increased approximately linearly with the electron energy in the electron energy range of several tens of MeV. The PXR energy increased linearly with the crystal rotation angle that depended on the reflection plane and the observation angle and did not depend on the electron energy. The obtained counts of PXR increased at large observation angles although the energy decreased. The experiments used Si plates with thicknesses of 200, 300, 400, 500, 530, and 625 mum. Differences in angular distribution by the thickness of the Si plates were established. The possibility for PXR applications to material research and other fields is discussed. The off angle of the polished (cut) plane of the crystal was accurately determined using the PXR and the attenuation coefficient around the K-shell absorption edge of Zr, Nb and Mo were measured. (C) 2001 Elsevier Science B.V. All rights reserved.

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