2022/04/05 更新

写真a

ヒラノ ヨシユキ
平野 祥之
HIRANO Yoshiyuki
所属
大学院医学系研究科 総合保健学専攻 バイオメディカルイメージング情報科学 准教授
大学院担当
大学院医学系研究科
学部担当
医学部(保健学科)
職名
准教授
連絡先
メールアドレス

学位 1

  1. 博士(理学) ( 2008年6月   大阪大学 ) 

研究分野 3

  1. その他 / その他  / 放射線科学

  2. その他 / その他  / 医学物理学

  3. ライフサイエンス / 放射線科学

経歴 10

  1. 名古屋大学   大学院医学系研究科 総合保健学専攻 バイオメディカルイメージング情報科学   准教授

    2020年4月 - 現在

  2. 名古屋大学   大学院医学系研究科 医療技術学専攻 医用量子科学   准教授

    2017年9月 - 2020年3月

  3. 群馬大学   医学系研究科 重粒子線医学研究センター   助教

    2014年11月 - 2017年9月

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    国名:日本国

  4. 群馬大学   医学系研究科 重粒子線医学研究センター   助教

    2014年11月 - 2017年9月

  5. 群馬大学   医学系研究科 重粒子線医学研究センター   助教

    2014年11月 - 2017年9月

  6. 千葉工業大学   工学部 教育センター物理学教室   非常勤講師

    2012年9月 - 2014年3月

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    国名:日本国

  7. 放射線医学総合研究所   分子イメージング研究センター 先端生体計測研究プログラム   博士研究員

    2011年7月 - 2014年10月

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    国名:日本国

  8. 国立循環器病研究センター   画像診断医学部   非常勤研究員

    2011年5月 - 2011年6月

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    国名:日本国

  9. 国立循環器病研究センター   画像診断医学部   流動研究員

    2010年7月 - 2011年4月

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    国名:日本国

  10. 国立循環器病研究センター   放射線医学部   流動研究員

    2008年4月 - 2010年6月

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    国名:日本国

▼全件表示

学歴 2

  1. 大阪大学   理学研究科   物理学専攻

    - 2008年3月

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    国名: 日本国

  2. 大阪大学   理学研究科   物理学専攻

    - 2008年3月

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    国名: 日本国

所属学協会 4

  1. 日本核医学学会

  2. 日本医学物理学会

  3. 日本核医学学会

  4. 日本医学物理学会

受賞 1

  1. IOP Publishing Outstanding Reviewer award

    2020年3月  

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    受賞区分:学会誌・学術雑誌による顕彰 

 

論文 54

  1. 3-D Optical Imaging System of Muon Beams Using a Silver Activated Zinc Sulfide (ZnS(Ag)) Sheet Combined With a Mirror

    Yamamoto Seiichi, Ninomiya Kazuhiko, Kawamura Naritoshi, Hirano Yoshiyuki

    IEEE TRANSACTIONS ON NUCLEAR SCIENCE   68 巻 ( 12 ) 頁: 2748 - 2752   2021年12月

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    記述言語:日本語   出版者・発行元:IEEE Transactions on Nuclear Science  

    Optical imaging of muon beams is a promising method for range estimations. However, our previous optical imaging method could only measure 2-D projection images. To measure the beam ranges and widths at any position of the muon beam, 3-D beam images are desired. For this purpose, we developed an optical imaging system using a silver-activated zinc sulfide (ZnS(Ag)) sheet combined with a mirror and a cooled charge-coupled device (CCD) camera. The ZnS(Ag) sheet was set in a black box and irradiated by a positive muon beam at the Japan Proton Accelerator Research Complex (J-PARC). Acrylic plates were used to absorb the muon beam. The measured optical images with different thicknesses of the acrylic plates were stacked and interpolated to create a 3-D optical image, and then the depth and lateral profiles were evaluated. From the depth profile derived from the 3-D image, the Bragg peak position could be estimated. The lateral profiles at the Bragg peak positions could also be derived. We confirmed that 3-D optical imaging was possible using the developed system with a ZnS(Ag) sheet. The system is promising for measuring muon beam distribution, conducting research on muons, and developing future muon radiotherapy.

    DOI: 10.1109/TNS.2021.3123164

    Web of Science

    Scopus

  2. Three-dimensional (3D) optical imaging of muon beam using a plastic scintillator plate in water

    Yamamoto Seiichi, Ninomiya Kazuhiko, Kawamura Naritoshi, Yabe Takuya, Hirano Yoshiyuki

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   1015 巻   2021年11月

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    記述言語:日本語   出版者・発行元:Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment  

    Although optical imaging of muon beams is a possible method for range determination, it has been limited to two-dimensional (2D) projection images. For the precise measurement of an optical image of a muon beam, three-dimensional (3D) imaging is desired. To measure a 3D optical image, we conducted optical imaging of muon beams using a plastic scintillator plate set in a water phantom. When this plate was immersed in the water phantom, irradiation with a positive muon beam was carried out from along the plate's sides. Optical images of the scintillator plate were acquired using a charge-coupled device (CCD) camera from the side during irradiation with a positive muon beam. The imaging system was moved in 10-mm steps perpendicular to the beam direction to acquire a set of sliced optical images of the beam. These sliced images were stacked and interpolated to form a 3D optical image, and the depth and lateral profiles were evaluated. From the depth profiles derived from the 3D optical image, the Bragg peak position was estimated. The lateral profiles at the Bragg peak could also be derived. We confirmed that 3D imaging of muon beams is feasible and in fact a promising method for measuring sliced optical images at any position, which is a capability that is useful for research on muon beams as well as for future muon radiotherapy.

    DOI: 10.1016/j.nima.2021.165768

    Web of Science

    Scopus

  3. Optical imaging of decayed positrons and muons with different collimators

    Yamamoto S., Ninomiya K., Kawamura N., Hirano Y.

    JOURNAL OF INSTRUMENTATION   16 巻 ( 8 )   2021年8月

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    記述言語:日本語   出版者・発行元:Journal of Instrumentation  

    Although optical imaging of decayed positrons and muons can provide promising methods, it has been attempted only for muons without a collimator, and the beam characteristics with collimators, such as peak position or beam spread in depth and lateral directions, have not yet been evaluated. Therefore, we conducted optical imaging of decayed positrons and muons with different collimators. For the imaging of decayed positrons, Cherenkov-light imaging in fluorescein (FS) water was used, while imaging of a plastic scintillator block was used for the imaging of muons. We conducted these imaging trials during irradiation with 84.5-MeV/c positive muons to an FS water phantom or a plastic scintillator block using a cooled charge-coupled device (CCD) camera with each collimator of a different diameter attached to the beam port. We could measure the Cherenkov-light images of FS water of decayed positrons and optical images of muons using the plastic scintillator block for all collimators. The depth profiles of the Cherenkov-light images were slightly wider for the muons with the collimators of larger diameters, although the estimated peak depths were nearly the same for all collimators. The lateral profiles of the Cherenkov light were wider for the muons when using collimators of larger diameters. Asymmetry in the directions of positron emissions from the muons was observed for all collimators. The depth profiles of the optical image of muons using a plastic scintillator block had nearly the same shape. The estimated lateral widths of the optical images of the plastic scintillator block were the same sizes as the collimator diameters within a 1.1-mm difference at a 10-mm depth of the scintillator block, and the widths were wider at the Bragg peak. With these measured optical images, we conclude that Cherenkov-light imaging of decayed positrons in water and optical imaging of muons using a plastic scintillator block with collimators are useful methods for determining not only peak position but also beam width as well as the asymmetry of the directions of positron emissions from the muons.

    DOI: 10.1088/1748-0221/16/08/P08062

    Web of Science

    Scopus

  4. Low background measurement in CANDLES-III for studying the neutrinoless double beta decay of Ca-48

    Ajimura S., Chan W. M., Ichimura K., Ishikawa T., Kanagawa K., Khai B. T., Kishimoto T., Kino H., Maeda T., Matsuoka K., Nakatani N., Nomachi M., Saka M., Seki K., Takemoto Y., Takihira Y., Tanaka D., Tanaka M., Tetsuno K., Trang V. T. T., Tsuzuki M., Umehara S., Akutagawa K., Batpurev T., Doihara M., Katagiri S., Kinoshita E., Hirano Y., Iga T., Ishikawa M., Ito G., Kakubata H., Lee K. K., Li X., Mizukoshi K., Moser M., Ohata T., Shokati M., Uehara T., Wang W., Yamamoto K., Yasuda K., Yoshida S., Yotsunaga N., Harada T., Hiraoka H., Hiyama T., Hirota A., Ikeyama Y., Kawamura A., Kawashima Y., Maeda S., Nakajima K., Ogawa I, Ozawa K., Shamoto K., Shimizu K., Shinki Y., Tamagawa Y., Tozawa M., Yoshizawa M., Fushimi K., Hazama R., Noithong P., Rittirong A., Suzuki K., Iida T.

    PHYSICAL REVIEW D   103 巻 ( 9 )   2021年5月

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    記述言語:日本語   出版者・発行元:Physical Review D  

    We developed a CANDLES-III system to study the neutrinoless double beta (0νββ) decay of Ca48. The proposed system employs 96 CaF2 scintillation crystals (305 kg) with natural Ca (Canat) isotope which corresponds 350 g of Ca48. External backgrounds were rejected using a 4π active shield of a liquid scintillator surrounding the CaF2 crystals. The internal backgrounds caused by the radioactive impurities within the CaF2 crystals can be reduced effectively through analysis of the signal pulse shape. We analyzed the data obtained in the Kamioka underground for a live-time of 130.4 days to evaluate the feasibility of the low background measurement with the CANDLES-III detector. Using Monte Carlo simulations, we estimated the background rate from the radioactive impurities in the CaF2 crystals and the rate of high energy γ-rays caused by the (n,γ) reactions induced by environmental neutrons. The expected background rate was in a good agreement with the measured rate, i.e., approximately 10-3 events/keV/yr/(kg of Canat), in the 0νββ window. In conclusion, the background candidates were estimated properly by comparing the measured energy spectrum with the background simulations. With this measurement method, we performed the first search for 0νββ decay in a low background condition using a detector on the scale of hundreds of kg of nonenriched Ca. Deploying scintillators enriched in Ca48 will increase the sensitivity strongly. Ca48 has a high potential for use in 0νββ decay search, and is expected to be useful for the development of a next-generation detector for highly sensitive measurements.

    DOI: 10.1103/PhysRevD.103.092008

    Web of Science

    Scopus

  5. A method to reduce the error due to the angular dependencies of Cerenkov-light in water for optical imaging of X-rays from high-energy medical linear accelerators (LINAC)

    Toyonaga C., Yamamoto S., Hirano Y., Okudaira K., Kato T., Sugita K.

    JOURNAL OF INSTRUMENTATION   16 巻 ( 3 )   2021年3月

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    記述言語:日本語   出版者・発行元:Journal of Instrumentation  

    Determining the absorbed dose distributions in phantoms for X-ray beams of high-energy medical linear accelerators (LINAC) is an important task in the quality control of a system. Although optical imaging of water during irradiation of X-ray beams from a LINAC is a promising method, depth dose profiles show underestimation in the deeper parts of the water, mainly due to the angular dependency of Cerenkov-light produced in water. To solve this problem, the authors change camera angles from 0 degree to 10 degrees and obtain optical images with a high-sensitivity cooled charge coupled device (CCD) camera during X-ray beam irradiation. Furthermore, the authors calculate the Cerenkov-light distributions with different camera angles using Monte Carlo simulation and the obtained depth profiles. Then, these depth profiles are evaluated and compared with those of a planning system. In both measured and simulated distributions, the light intensity increases as the angle increases. The measured depth profile of 10 degrees was nearly identical to the planning system. The percentage differences of depth profile between the measured optical image at the angle of 10 degrees and the planning system was -1.7 % at 100 mm depth, and the average difference was 0.8 %. We conclude that optical imaging with that angle is a promising method for reducing the error due to the angular dependency of Cerenkov-light.

    DOI: 10.1088/1748-0221/16/03/T03001

    Web of Science

    Scopus

  6. Calculation of Stopping-Power Ratio from Multiple CT Numbers Using Photon-Counting CT System: Two- and Three-Parameter-Fitting Method

    Lee Sung Hyun, Sunaguchi Naoki, Nagao Akie, Hirano Yoshiyuki, Sakurai Hiroshi, Kano Yosuke, Torikoshi Masami, Kanai Tatsuaki, Tashiro Mutsumi

    SENSORS   21 巻 ( 4 ) 頁: 1 - 21   2021年2月

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    記述言語:日本語   出版者・発行元:Sensors (Switzerland)  

    The two-parameter-fitting method (PFM) is commonly used to calculate the stoppingpower ratio (SPR). This study proposes a new formalism: a three-PFM, which can be used in multiple spectral computed tomography (CT). Using a photon-counting CT system, seven rod-shaped samples of aluminium, graphite, and poly(methyl methacrylate) (PMMA), and four types of biological phantom materials were placed in a water-filled sample holder. The X-ray tube voltage and current were set at 150 kV and 40 μA, respectively, and four CT images were obtained at four threshold settings. A semi-empirical correction method that corrects the difference between the CT values from the photon-counting CT images and theoretical values in each spectral region was also introduced. Both the two-and three-PFMs were used to calculate the effective atomic number and electron density from multiple CT numbers. The mean excitation energy was calculated via parameterisation with the effective atomic number, and the SPR was then calculated from the calculated electron density and mean excitation energy. Then, the SPRs from both methods were compared with the theoretical values. To estimate the noise level of the CT numbers obtained from the photoncounting CT, CT numbers, including noise, were simulated to evaluate the robustness of the aforementioned PFMs. For the aluminium and graphite, the maximum relative errors for the SPRs calculated using the two-PFM and three-PFM were 17.1% and 7.1%, respectively. For the PMMA and biological phantom materials, the maximum relative errors for the SPRs calculated using the twoPFM and three-PFM were 5.5% and 2.0%, respectively. It was concluded that the three-PFM, compared with the two-PFM, can yield SPRs that are closer to the theoretical values and is less affected by noise.

    DOI: 10.3390/s21041215

    Web of Science

    Scopus

    PubMed

  7. Position distribution calculation of annihilation radiations and bremsstrahlung x rays in water during irradiation of positive muons: a Monte Carlo simulation study

    Hirano Yoshiyuki, Yamamoto Seiichi, Kawamura Naritoshi, Ninomiya Kazuhiko

    PHYSICA SCRIPTA   96 巻 ( 2 )   2021年2月

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    記述言語:日本語   出版者・発行元:Physica Scripta  

    Range, momentum and deviation of momentum determinations of muons are important for quality assessment (QA) of beams. Imaging of annihilation radiations emitted from positrons decayed from positive muons and that of bremsstrahlung x-rays emitted from positrons and secondary electrons from positive muons are possible methods of imaging muons. However, the energies and intensities as well as position distributions of these radiations have not been obvious. Thus we calculated the energy spectrum and the distributions of annihilation radiations as well as bremsstrahlung x-rays produced in water during irradiation of positive muons using Monte Carlo simulation. The calculations were conducted for 84.5 MeV /c positive muons, which is the same beam condition used in an experimental facility at the Japan Proton Accelerator Research Complex (J-PARC). We were able to calculate the energy spectrum as well as the position distributions of annihilation radiations and bremsstrahlung x-rays. The energy spectrum showed a broad distribution of bremsstrahlung x-rays, mainly from decayed positrons with an energy range up to 50 MeV with higher intensity in low-energy bremsstrahlung x-rays. The spectrum also showed a sharp peak at 511-keV from annihilation radiations. The position distribution of annihilation radiations was wider than those of the bremsstrahlung x-rays. The position distribution of the bremsstrahlung x-rays were nearly identical to the Cerenkov-light position distribution emitted by the decayed positrons in water. We conclude that imaging of bremsstrahlung x-rays from decayed positrons by using an x-ray camera is a promising method for the QA of positive muons and that higher spatial resolution images of positron distributions will be measured than those measured by annihilation radiations.

    DOI: 10.1088/1402-4896/abcf65

    Web of Science

    Scopus

  8. Imaging of polarized components of Cerenkov light and luminescence of water during carbon-ion irradiation 国際誌

    Yamamoto Seiichi, Yabe Takuya, Akagi Takashi, Hirano Yoshiyuki

    MEDICAL PHYSICS   48 巻 ( 1 ) 頁: 427 - 433   2021年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Medical Physics  

    Purpose: The luminescence image of water during the irradiation of carbon ions showed higher intensity at shallow depths than dose distribution due to the contamination of Cerenkov light from secondary electrons. Since Cerenkov light is coherent and polarized for the light produced during the irradiation of carbon ions to water, the reduction of Cerenkov light may be possible with a polarizer. In addition, there is no information on the polarization of the luminescence of water. To clarify these points, we measured the optical images of water during the irradiation of carbon ions with a polarizer by changing the directions of the transmission axis. Methods: Imaging was conducted using a cooled charge-coupled device (CCD) camera during the irradiation of 241.5 MeV/n energy carbon ions to a water phantom with a polarizer in front of the lens by changing the transmission axis parallel and perpendicular to the carbon-ion beam. Results: With the polarizer parallel to the carbon-ion beam, the intensity at the shallow depth was ~26% higher than that measured with the polarizer perpendicular to the beam. We found no significant intensity difference between these two images at deeper depths where the Cerenkov light was not included. The difference image of the parallel and perpendicular directions showed almost the same image as the simulated Cerenkov light distribution. Using the measured difference image, correction of the Cerenkov component was possible from the measured luminescence image of water during the irradiation of carbon ions. Conclusion: We could measure the difference of the Cerenkov light component by changing the transmission axis of the polarizer. Also we clarified that there was no difference in the luminescence of water by changing the transmission axis of the polarizer.

    DOI: 10.1002/mp.14600

    Web of Science

    Scopus

    PubMed

  9. Optical imaging of muons

    Yamamoto Seiichi, Ninomiya Kazuhiko, Kawamura Naritoshi, Hirano Yoshiyuki

    SCIENTIFIC REPORTS   10 巻 ( 1 ) 頁: 20790   2020年12月

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    記述言語:日本語   出版者・発行元:Scientific Reports  

    Optical imaging of particle beams is a promising method for range and width estimations. However it was not clear that optical imaging was possible for muons. To clarify this, we conducted optical imaging of muons, since high-intensity muons are now available at J-PARC. We irradiated positive muons with different momenta to water or plastic scintillator block, and imaged using a charge-coupled device (CCD) camera during irradiation. The water and plastic scintillator block produced quite different images. The images of water during irradiation of muons produced elliptical shape light distribution at the end of the ranges due to Cherenkov-light from the positrons produced by positive muon decay, while, for the plastic scintillator block, we measured images similar to the dose distributions. We were able to estimate the ranges of muons as well as the measurement of the asymmetry of the direction of the positron emission by the muon decays from the optical images of the water, although the measured ranges were 4 mm to 5 mm larger than the calculated values. The ranges and widths of the beams could also be estimated from the optical images of the plastic scintillator block. We confirmed that optical imaging of muons was possible and is a promising method for the quality assessment, research of muons, and the future muon radiotherapy.

    DOI: 10.1038/s41598-020-76652-8

    Web of Science

    Scopus

    PubMed

  10. Can B Washout Rate be a Biomarker of Tumor Viability in Charged Particle Therapy? A Rat In-beam PET Study

    Toramatsu C., Mohammadi A., Wakizaka H., Seki C., Kanno I., Karasawa K., Hirano Y., Yamaya T.

    INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS   108 巻 ( 3 ) 頁: E254 - E254   2020年11月

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    記述言語:日本語  

    Web of Science

  11. Biological washout effect in in-beam PET: Animal studies

    Toramatsu C., Mohammadi A., Wakizaka H., Seki C., Nishikido F., Sato S., Kanno I., Takahashi M., Karasawa K., Hirano Y., Yamaya T.

    Journal of Physics: Conference Series   1662 巻 ( 1 )   2020年10月

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    記述言語:日本語   出版者・発行元:Journal of Physics: Conference Series  

    Positron emission tomography (PET) is a practical tool for range verification of hadron therapy. As well, the quantitative washout of the positron emitters has a potential usefulness as a diagnostic index, but the modelling for this has not been established. In this study, we measured washout rates of rabbit brain and performed kinetic analysis to explore the washout mechanism. Six rabbit brains were irradiated by 11C and 15O ion beams, and dynamic PET scan was performed using our original depth of interest (DOI)-PET prototype. The washout rate was obtained based on the two-compartment model, where efflux from tissue to blood (k2), influx (k3) and efflux (k4) from the first to second compartments in tissue were evaluated. The observed k2, k3 and k4 of 11C were 0.086, 0.137 and 0.007 min-1, and those of 15O were 0.502, 0.360 and 0.007 min-1, respectively. It was suggested permeability of a molecule containing 11C atoms might be regulated by a transporter. The k2 of 15O was comparable with 15O-water. This study provides basic data for modelling of the washout effect.

    DOI: 10.1088/1742-6596/1662/1/012032

    Scopus

  12. Measurements of temporal response of luminescence of water at lower energy than Cerenkov-light threshold during carbon-ion irradiation

    Yamamoto Seiichi, Akagi Takashi, Hirano Yoshiyuki, Komori Masataka

    BIOMEDICAL PHYSICS & ENGINEERING EXPRESS   6 巻 ( 4 ) 頁: 045002   2020年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Biomedical Physics and Engineering Express  

    Although the luminescence of water at lower energy than the Cerenkov-light threshold during carbon-ion irradiation was found and imaging was possible, the temporal response has not been measured, and so the difference from Cerenkov-light remains unclear. To clarify this point, we measured the temporal response of the luminescence of water at lower energy than the Cerenkov-light threshold and compared it with that of Cerenkov-light. We used silicon photomultiplier (Si-PM) modules to measure the temporal response at the Bragg peak area of a water phantom during irradiation of the carbon ion where the Cerenkov-light was not included. We also measured the temporal response at the shallow depth of the water phantom where the Cerenkov-light was included. In both areas, we measured the temporal waveforms of the light produced by the irradiation of the carbon ions in which the ripples of spills were clearly observed. We found no difference in the waveforms between the Bragg peak and the shallow depths of water. Our results do not contradict the hypothesis that the luminescence of water and Cerenkov-light are produced by the same mechanism.

    DOI: 10.1088/2057-1976/ab8b7e

    Web of Science

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    PubMed

  13. Radioluminescence by synchrotron radiation with lower energy than the Cherenkov light threshold in water

    Hirano Yoshiyuki, Komori Masataka, Onoda Daichi, Nagae Takayuki, Yamamoto Seiichi

    JOURNAL OF PHYSICS COMMUNICATIONS   4 巻 ( 7 )   2020年7月

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    記述言語:日本語   出版者・発行元:Journal of Physics Communications  

    Radioluminescence by protons and carbon ions of energy lower than the Cherenkov threshold (∼260 keV) in water has been observed. However, the origin of the luminescence has not been investigated well. In the present work, we imaged radioluminescence in water using synchrotron radiation that was of sufficiently lower energy (11 keV) than the Cherenkov threshold and we measured its spectrum using a high-sensitivity cooled CCD camera and optical longpass filters having 5 different thresholds. In addition, to determine effects of impurities in water, the water target was changed from ultrapure water to tap water. Monte Carlo simulation (Geant4) was also performed to compare its results with the experimentally obtained radioluminescence distribution. In the simulation, photons were generated in proportion to the energy deposition in water. As a result, the beam trajectory was clearly imaged by the radioluminescence in water. The spectrum was proportional to λ−3.4±0.4 under an assumption of no peaks. In the spectrum and distribution, no differences were observed between ultrapure water and tap water. TOC (total organic carbon) contents of ultrapure water and tap water as an impurity were measured and these were 0.26 mg l−1 and 2.3 mg l−1, respectively. The radioluminescence seemed to be attributable to water molecules not impurities. The radioluminescence distribution of the simulation was consistent with the experimental distribution and this suggested that radioluminescence was proportional to dose, which is expected to allow use for dose measurement.

    DOI: 10.1088/2399-6528/ab9f8d

    Web of Science

    Scopus

  14. Development of an ultrahigh-resolution radiation real-time imaging system to observe trajectory of alpha particles in a scintillator

    Yamamoto Seiichi, Hirano Yoshiyuki, Kamada Kei, Yoshikawa Akira

    RADIATION MEASUREMENTS   134 巻   2020年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Radiation Measurements  

    The high-resolution imaging of alpha particles is required for the development of radio-compounds for targeted alpha-particle therapy or alpha emitter detection at nuclear facilities. Therefore, we developed an ultrahigh-resolution, real-time alpha-particle imaging system for observing the trajectories of alpha particles in a scintillator. The developed alpha-particle imaging system is made from a 1-μm-diameter fiber-structure scintillator plate that is optically coupled with the first of two sequentially connected tapered optical fiber plates. The output of the second, larger tapered optical fiber plate was imaged by an electron-multiplied (EM) cooled CCD camera. With our developed imaging system, we observed images of alpha particles having a spatial resolution of ~11 μm. We could also observe the trajectories of alpha particles with Bragg peaks for the angled incident alpha particles. We conclude that this imaging system, which can observe the trajectory of alpha particles in a fiber-structure scintillator, is promising for research on targeted alpha-particle therapy or alpha emitter detection at nuclear facilities.

    DOI: 10.1016/j.radmeas.2020.106368

    Web of Science

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  15. Biological washout modelling for in-beam PET: rabbit brain irradiation by C-11 and O-15 ion beams

    Toramatsu Chie, Mohammadi Akram, Wakizaka Hidekazu, Seki Chie, Nishikido Fumihiko, Sato Shinji, Kanno Iwao, Takahashi Miwako, Karasawa Kumiko, Hirano Yoshiyuki, Yamaya Taiga

    PHYSICS IN MEDICINE AND BIOLOGY   65 巻 ( 10 ) 頁: 105011   2020年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics in Medicine and Biology  

    Positron emission tomography (PET) has been used for dose verification in charged particle therapy. The causes of washout of positron emitters by physiological functions should be clarified for accurate dose verification. In this study, we visualized the distribution of irradiated radioactive beams, 11C and 15O beams, in the rabbit whole-body using our original depth-of-interaction (DOI)-PET prototype to add basic data for biological washout effect correction. Time activity curves of the irradiated field and organs were measured immediately after the irradiations. All data were corrected for physical decay before further analysis. We also collected expired gas of the rabbit during beam irradiation and the energy spectrum was measured with a germanium detector. Irradiated radioactive beams into the brain were distributed to the whole body due to the biological washout process, and the implanted 11C and 15O ions were concentrated in the regions which had high blood volume. The 11C-labelled 11CO2 was detected in expired gas under the 11C beam irradiation, while no significant signal was detected under the 15O beam irradiation as a form of C15O2. Results suggested that the implanted 11C ions form molecules that diffuse out to the whole body by undergoing perfusion, then, they are incorporated into the blood-gas exchange in the respiratory system. This study provides basic data for modelling of the biological washout effect.

    DOI: 10.1088/1361-6560/ab8532

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  16. Scintillator screen for measuring low-dose halo in scanning carbon-ion therapy

    Yogo Katsunori, Tatsuno Yuya, Souda Hikaru, Matsumura Akihiko, Tsuneda Masato, Hirano Yoshiyuki, Ishiyama Hiromichi, Saito Akito, Ozawa Shuichi, Nagata Yasushi, Nakano Takashi, Hayakawa Kazushige, Kanai Tatsuaki

    RADIATION MEASUREMENTS   133 巻   2020年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Radiation Measurements  

    To ensure safe administration and quality assurance (QA) of scanning carbon-ion therapy doses, an efficient and reliable method to measure the lateral dose profile of a carbon-ion pencil beam, including the low-dose halo, is required. We developed a simple, expeditious dose measurement tool that employs a silver-activated zinc sulfide (ZnS) scintillator, which shows a low linear energy transfer (LET) dependency, to measure the low-dose halo of a carbon-ion pencil beam with high spatial resolution.

    DOI: 10.1016/j.radmeas.2020.106299

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  17. Estimations of relative biological effectiveness of secondary fragments in carbon ion irradiation of water using CR-39 plastic detector and microdosimetric kinetic model. 査読有り

    Hirano Y, Kodaira S, Souda H, Osaki K, Torikoshi M

    Medical physics   47 巻 ( 2 ) 頁: 781 - 789   2020年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Medical Physics  

    Purpose: To estimate relative biological effectiveness (RBE) ascribed to secondary fragments in a lateral distribution of carbon ion irradiation. The RBE was estimated with the microdosimetric kinetic (MK) model and measured linear energy transfer (LET) obtained with CR-39 plastic detectors. Methods: A water phantom was irradiated by a 12C pencil beam with energy of 380 MeV/u at the Gunma University Heavy Ion Medical Center (GHMC), and CR-39 detectors were exposed to secondary fragments. Because CR-39 was insensitive to low LET, we conducted Monte Carlo simulations with Geant4 to calculate low LET particles. The spectra of low LET particles were combined with experimental spectra to calculate RBE. To estimate accuracy of RBE, we calculated RBE by changing yield of low LET particles by ± 10% and ± 40%. Results: At a small angle, maximum RBE by secondary fragments was 1.3 for 10% survival fractions. RBE values of fragments gradually decreased as the angle became larger. The shape of the LET spectra in the simulation reproduced the experimental spectra, but there was a discrepancy between the simulation and experiment for the relative yield of fragments. When the yield of low LET particles was changed by ± 40%, the change in RBE was smaller than 10%. Conclusions: An RBE of 1.3 was expected for secondary fragments emitted at a small angle. Although, we observed a discrepancy in the relative yield of secondary fragments between simulation and experiment, precision of RBE was not so sensitive to the yield of low LET particles.

    DOI: 10.1002/mp.13916

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  18. Estimation of dose and light distributions in water during irradiation of muon beams

    Hirano Yoshiyuki, Ninomiya Kazuhiko, Yamamoto Seiichi

    PHYSICA SCRIPTA   94 巻 ( 12 )   2019年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Scripta  

    High-intensity muon beams are now available at the Japan Proton Accelerator Research Complex and their use in radiotherapy may become possible in the future. Dose and range estimation are therefore important and optical imaging of the dose or range may be a promising method for that purpose. We calculated the dose and light distributions in water during irradiation of a positive muon beam using Monte Carlo simulation. First, we simulated the dose deposited in water for pencil beams with 30 and 50 MeV positive muons. We were able to clearly identify the Bragg peak in the depth dose profiles by muons and observed that the dose from positrons are added to the Bragg peak area with a ∼10% muon dose. We also found that the lateral dose widths increased as the depth increased and that it was ∼3-5 times wider at the Bragg peak position. With the light distribution of the muon in water, light produced by the positrons was dominant and distributed around the Bragg peak, and the peak positions were estimated within 2 mm differences of the peak position of the dose distributions. It is therefore possible to monitor the Bragg peak position of muons using an optical method.

    DOI: 10.1088/1402-4896/ab3acb

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  19. Scintillator screen for measuring dose distribution in scanned carbon-ion therapy 査読有り

    Yogo Katsunori, Tatsuno Yuya, Souda Hikaru, Matsumura Akihiko, Tsuneda Masato, Hirano Yoshiyuki, Ishiyama Hiromichi, Saito Akito, Ozawa Shuichi, Nagata Yasushi, Nakano Takashi, Hayakawa Kazushige, Kanai Tatsuaki

    RADIATION MEASUREMENTS   129 巻   2019年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Radiation Measurements  

    Precise measurement of the dose distribution of a carbon-ion pencil beam is essential for the safe delivery of treatment in scanned carbon-ion therapy. We developed an easy-to-use and quick dose-measurement tool that employs a silver-activated zinc-sulfide (ZnS) scintillator, which shows a smaller linear energy transfer (LET) dependency than conventional Gd-based scintillator, to measure the dose distribution of a carbon-ion pencil beam with high spatial resolution and small corrections. A ZnS scintillator sheet was set up perpendicular to the beam axis, and scintillation images were recorded using a charge-coupled device camera. We used 290-MeV/nucleon monoenergetic carbon-ion pencil beams at the Gunma University Heavy Ion Medical Center. The thickness of the water tank placed above the scintillator was remotely controlled to adjust the measurement depth. Images were acquired at different water depths, and the depth and lateral profiles were determined from the images. The results were compared with those of conventional Gd-based scintillator. The depth–light intensity profile of the ZnS scintillator matched the depth dose measured using an ionization chamber, which was better than that of a Gd-based scintillator. This result is advantageous for measurements using a carbon-ion pencil beam, which consists of primary carbon ions with a much higher LET than a proton, with smaller corrections. The ZnS scintillator showed good output characteristics, dose linearity (R2 > 0.99), and output reproducibility (deviations below 2%) and good agreement with the lateral-dose profiles measured using a diode down to ~1% of the central dose. The proposed tool can measure lateral profiles at the depth of the Bragg peak and tail in addition to the entrance. Our tool was used to quickly measure the dose distribution of carbon-ion pencil beam with high-spatial resolution and small corrections.

    DOI: 10.1016/j.radmeas.2019.106207

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  20. Estimation of the fractions of luminescence of water at higher energy than Cerenkov-light threshold for various types of radiation 国際誌

    Hirano Yoshiyuki, Yamamoto Seiichi

    JOURNAL OF BIOMEDICAL OPTICS   24 巻 ( 6 ) 頁: 1 - 9   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Biomedical Optics  

    Although the luminescence of water at a lower energy than the Cerenkov-light (CL) threshold has been found for various types of radiation, the fractions of the luminescence of water to the total produced light have not been obvious for radiations at a higher energy than the CL threshold because it is difficult to separate these two types of light. Thus, we used a Monte Carlo simulation to estimate the fractions of the luminescence of water for various types of radiation at a higher energy than the CL threshold to confirm the major component of the produced light. After we confirmed that the estimated light production of the luminescence of water could adequately simulate the experimental results, we calculated the produced light photons of this luminescence and the CL from water for protons (170 MeV), carbon ions (330 MeV/n), high-energy x-ray (6 MV) from a linear accelerator (LINAC), high-energy electrons (9 MeV) from LINAC, positrons (F-18, C-11, O-15, and N-13), and high-energy gamma photon radionuclides (Co-60). For protons, the major fraction of the produced light was the luminescence of water in addition to the CL from the prompt gamma photons produced by the nuclear interactions. For carbon ions, the major fraction of the produced light was the luminescence of water and the CL produced by the secondary electrons in addition to the prompt gamma photons produced by the nuclear interactions. For high-energy x-ray and electrons from LINAC, the fractions of luminescence of water were 1/40.1 % to 0.2%. The fractions of luminescence of water for positrons were 0.2% to 1.5% and that for Co-60 was 0.4%. We conclude that the major fractions of light produced from x-ray and electrons from LINAC, positron radionuclides, and the Co-60 source are CL, with fractions of the luminescence of water from <0.1 % to 1.5%.

    DOI: 10.1117/1.JBO.24.6.066005

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  21. Estimation of the three-dimensional (3D) dose distribution of electron beams from medical linear accelerator (LINAC) using plastic scintillator plate

    Horita Ryo, Yamamoto Seiichi, Yogo Katsunori, Hirano Yoshiyuki, Okudaira Kuniyasu, Kawabata Fumitaka, Nakaya Takayoshi, Komori Masataka, Oguchi Hiroshi

    RADIATION MEASUREMENTS   124 巻   頁: 103 - 108   2019年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Radiation Measurements  

    Measurements of three-dimensional (3D) dose distribution of electron-beams in water are important for high-energy electron beams from medical linear accelerators (LINAC). Although ionization chambers are commonly used for this purpose, measurements take a long time for precise 3D dose distribution. To solve the problem, we tried the measurements of the 3D dose distributions using a scintillator plate combined with a mirror. After we placed a 1 mm thick plastic scintillator plate at the upper inside of a black box, a water phantom was set above the plastic scintillator plate outside the black box, and electron beam was irradiated to the water phantom from the upper side. The attenuated electron-beam by the water in the phantom was detected by the plastic scintillator plate and the scintillation image was formed in the plate. The image was reflected by a surface mirror set below the plastic scintillator plate and detected by a cooled charge coupled device (CCD) camera from the side. We changed the depths of the water in the phantom, obtained the scintillation images, and calculated a 3D scintillation image using the measured images. Measurements were made for 9 MeV and 12 MeV electron-beams using the imaging system. From the images, we could successfully form 3D scintillation images. The depth profiles measured from the 3D images showed almost identical distribution with those calculated by the planning system within the difference of 5%. The lateral profiles also showed almost identical within the difference of the widths less than 2.5 mm. We conclude that the proposed method is promising for 3D dose distribution measurements of electron-beams.

    DOI: 10.1016/j.radmeas.2019.04.002

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  22. Comparison of Noise Equivalent Count Rates (NECRs) for the PET Systems With Different Ring Diameter and Electronics

    Nakanishi Kouhei, Hirano Yoshiyuki, Yamamoto Seiichi

    IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES   3 巻 ( 3 ) 頁: 371 - 376   2019年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Transactions on Radiation and Plasma Medical Sciences  

    Because the sensitivity of positron emission tomography (PET) system increases in proportion to the inverse of the diameter of the detector ring, brain PET systems are being planned and developed. However, count losses due to the dead-time of the detector blocks increases as the ring diameter decreases. Since the count losses decrease the noise equivalent count rate (NECR) of the system, the NECR of brain PET system may be lower than that of a whole-body PET system in clinical dose range. In this paper, we compared the NECRs of brain PET systems with that of a whole-body PET system using a Monte Carlo simulation. We simulated the PET system for a 27-cm-diameter detector ring, a 54-cm-diameter detector ring, and an 89-cm-diameter detector ring and evaluated the NECRs. In the clinical dose range, the NECR of the small-diameter brain PET system was lower than those of the whole-body PET system unless the electronics was advanced. We conclude that the small-diameter brain PET system with conventional electronics has not so much advantage except for the lower cost and the higher spatial resolution. However, advanced electronics can reduce degradation of NECR, so the small-diameter brain PET system with advanced electronics will be useful for clinical studies.

    DOI: 10.1109/TRPMS.2018.2876410

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  23. Angular dependencies of Cerenkov-light in water for carbon-ion, high energy x-ray and electron

    Hirano Yoshiyuki, Yamamoto Seiichi

    BIOMEDICAL PHYSICS & ENGINEERING EXPRESS   5 巻 ( 2 )   2019年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Biomedical Physics and Engineering Express  

    Because Cerenkov light is emitted above the threshold energy of the electrons (∼260 keV) in water and is emitted to forward directions, the light intensity distributions are different from the dose for x-ray and electron from LINAC. Cerenkov-light component was also observed with the depth profiles in carbon-ion. However the angular dependencies of the Cerenkov-light distributions were not obvious. Thus we calculated the depth profiles of the produced light distributions for 240 MeV n-1 carbon-ion, 6 MV x-ray, and 9 MeV electrons using Monte Carlo simulation. After we confirmed the simulation accuracies by comparing with the measured results, we calculated the depth profiles of luminescence of water and Cerenkov-light with various angles for these three types of radiations. With the simulation results, it became obvious that the depth profiles were significantly different with the angles for the produced light containing the Cerenkov-light. Cerenkov-light components were much higher at the larger angles. We also found the almost identical depth profile to dose with the angle of 10 degree to the right angle of the beam direction for 6 MV x-ray.

    DOI: 10.1088/2057-1976/ab05b0

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  24. Linear energy transfer (LET) spectra and survival fraction distribution based on the CR-39 plastic charged-particle detector in a spread-out Bragg peak irradiation by a C-12 beam

    Hirano Yoshiyuki, Kodaira Satoshi, Souda Hikaru, Matsumura Akihiko, Torikoshi Masami

    PHYSICS IN MEDICINE AND BIOLOGY   63 巻 ( 18 ) 頁: 185006   2018年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics in Medicine and Biology  

    Facilities for heavy ion therapies are steadily increasing in number worldwide. One of the advantages of heavy ions is their high relative biological effect (RBE). In a model used at NIRS (National Institute of Radiological Sciences), linear energy transfer (LET) spectra are required to estimate biological dose (physical dose × RBE). The CR-39 plastic charged-particle detector (CR-39) is suitable for measurement of LET. For the present study, done at the Gunma University Heavy Ion Medical Center (GHMC), we measured LET spectra at 11 depths in spread-out Bragg peak (SOBP) irradiation by a 12C beam of 380 MeV/u. The lower threshold of the CR-39 to measure LET was about 5 keV μm-1 due to poor sensitivity for low LET. Then we calculated biological dose and survival fraction distributions and compared them with treatment planning results at GHMC. We used Monte Carlo simulation (Geant4) to calculate LET spectra. The simulation results were in good agreement with the experimental spectra. Moreover, the biological dose and survival fraction distributions estimated from the CR-39 reproduced the treatment planning. The CR-39 is suitable for estimating biological dose in carbon ion therapy.

    DOI: 10.1088/1361-6560/aadaa6

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  25. Addition of luminescence process in Monte Carlo simulation to precisely estimate the light emitted from water during proton and carbon-ion irradiation

    Yabe Takuya, Sasano Makoto, Hirano Yoshiyuki, Toshito Toshiyuki, Akagi Takashi, Yamashita Tomohiro, Hayashi Masateru, Azuma Tetsushi, Sakamoto Yusuku, Komori Masataka, Yamamoto Seiichi

    PHYSICS IN MEDICINE AND BIOLOGY   63 巻 ( 12 ) 頁: 125019   2018年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics in Medicine and Biology  

    Although luminescence of water lower in energy than the Cerenkov-light threshold during proton and carbon-ion irradiation has been found, the phenomenon has not yet been implemented for Monte Carlo simulations. The results provided by the simulations lead to misunderstandings of the physical phenomenon in optical imaging of water during proton and carbon-ion irradiation. To solve the problems, as well as to clarify the light production of the luminescence of water, we modified a Monte Carlo simulation code to include the light production from the luminescence of water and compared them with the experimental results of luminescence imaging of water. We used GEANT4 for the simulation of emitted light from water during proton and carbon-ion irradiation. We used the light production from the luminescence of water using the scintillation process in GEANT4 while those of Cerenkov light from the secondary electrons and prompt gamma photons in water were also included in the simulation. The modified simulation results showed similar depth profiles to those of the measured data for both proton and carbon-ion. When the light production of 0.1 photons/MeV was used for the luminescence of water in the simulation, the simulated depth profiles showed the best match to those of the measured results for both the proton and carbon-ion compared with those used for smaller and larger numbers of photons/MeV. We could successively obtain the simulated depth profiles that were basically the same as the experimental data by using GEANT4 when we assumed the light production by the luminescence of water. Our results confirmed that the inclusion of the luminescence of water in Monte Carlo simulation is indispensable to calculate the precise light distribution in water during irradiation of proton and carbon-ion.

    DOI: 10.1088/1361-6560/aac74b

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  26. Washout effect in rabbit brain: in-beam PET measurements using C-10, C-11 and O-15 ion beams

    Toramatsu Chie, Yoshida Eiji, Wakizaka Hidekazu, Mohammadi Akram, Ikoma Yoko, Tashima Hideaki, Nishikido Fumihiko, Kitagawa Atsushi, Karasawa Kumiko, Hirano Yoshiyuki, Yamaya Taiga

    BIOMEDICAL PHYSICS & ENGINEERING EXPRESS   4 巻 ( 3 )   2018年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Biomedical Physics and Engineering Express  

    In particle therapy, in-beam positron emission tomography (PET) is expected to enable in situ noninvasive confirmation of the treatment delivery. For accurate range and dose verification or three-dimensional (3D) volume imaging, however, correction of the biological washout effect in a living body is necessary. In this study, we measured the washout rate in a rabbit brain using the recently developed technology for oxygen beam radiation as well as carbon ion beam radiation. To measure components of washout, three radionuclides, 10C, 11C and 15O, which were generated as secondary beams in the Heavy Ion Medical Accelerator in Chiba (HIMAC), were irradiated on the rabbit brain under two conditions, live and dead. In-beam data were acquired by our whole body dual-ring OpenPET, which enables 3D in-beam imaging. Regions of interests (ROIs) were set as a 3D positron distribution and the time activity curves (TACs) of the irradiated field were acquired. We obtained the washout rate for those conditions based on multiple component model analysis. A difference between washout speed in 11C ions and the 15O ions was observed. The observed medium and slow biological decay rates of 11C ions in rabbit brain were 0.30 min-1 and 0.004 min-1, respectively. Those values were consistent with the previous rabbit study results acquired by other imaging modalities, such as the pair of positron cameras or our single-ring small animal OpenPET prototype. The observed medium and slow biological decay rates of 15O ions were 0.72 min-1 and 0.024 min-1, respectively, which were faster than those of the 11C ion. Also, the medium biological decay rate of 15O ions was close to the washout rate in cerebral blood flow (CBF) measurements by dynamic PET with 15O-labeled water. These results should help to establish an accurate washout correction model.

    DOI: 10.1088/2057-1976/aaade7

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  27. A carbon CT system: how to obtain accurate stopping power ratio using a Bragg peak reduction technique.

    Lee SH, Sunaguchi N, Hirano Y, Kano Y, Liu C, Torikoshi M, Ohno T, Nakano T, Kanai T

    Physics in medicine and biology   63 巻 ( 3 ) 頁: 035025   2018年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6560/aaa453

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  28. Predictors of biologic discontinuation due to insufficient response in patients with rheumatoid arthritis who achieved clinical remission with biologic treatment: A multicenter observational cohort study

    Asai Shuji, Fujibayashi Takayoshi, Oguchi Takeshi, Hanabayashi Masahiro, Hayashi Masatoshi, Matsubara Hiroyuki, Ito Takayasu, Yabe Yuichiro, Watanabe Tsuyoshi, Hirano Yuji, Kanayama Yasuhide, Kaneko Atsushi, Kato Takefumi, Takagi Hideki, Takahashi Nobunori, Funahashi Koji, Takemoto Toki, Asai Nobuyuki, Watanabe Tatsuo, Ishiguro Naoki, Kojima Toshihisa

    MODERN RHEUMATOLOGY   28 巻 ( 2 ) 頁: 221 - 226   2018年

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    出版者・発行元:Modern Rheumatology  

    DOI: 10.1080/14397595.2017.1332558

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  29. Influences of 3D PET scanner components on increased scatter evaluated by a Monte Carlo simulation. 査読有り

    Hirano Y, Koshino K, Iida H

    Physics in medicine and biology   62 巻 ( 10 ) 頁: 4017 - 4030   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6560/aa6644

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  30. Induced radioactivity of a GSO scintillator by secondary fragments in carbon ion therapy and its effects on in-beam OpenPET imaging 査読有り

    Hirano Y, Nitta M, Nishikido F, Yoshida E, Inadama N, Yamaya T

      61 巻   頁: 4870-89   2016年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/0031-9155/61/13/4870

  31. Washout rate in rat brain irradiated by a 11C beam after acetazolamide loading using a small single-ring OpenPET prototype 査読有り

    Hirano Y, Takuwa H, Yoshida E, Nisikido F, Nakajima Y, Wakizaka H, Yamaya T

    Phys. Med. Biol   61 巻   頁: 1875-87   2016年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/0031-9155/61/5/1875

  32. After-pulsing, cross-talk, dark-count, and gain of MPPC under 7-T static magnetic field 査読有り

    Hirano Y, Nishikido F, Kokuryo D, Yamaya T

    Radiol. Phys. Technol.   9 巻   頁: 245-53   2016年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1007/s12194-016-0356-3

  33. Development of a DOI PET Detector Having the Structure of the X'tal Cube Extended in One Direction 査読有り

    Inadama N, Hirano Y, Nishikido F, Murayama H, Yamaya T

    IEEE Trans. On Nucl. Science   63 巻   頁: 2509-16   2016年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  34. Monte Carlo simulation of small OpenPET prototype with 11C beam irradiation: effects of secondary particles on in-beam imaging 査読有り

    Hirano Y, Yoshida E, Kinouchi S, Nishikido F, Inadma N, Murayama H, Yamaya T

    Phys. Med. Biol.   59 巻   頁: 1623-40   2014年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/0031-9155/59/7/1623

  35. Performance evaluation of a depth-of-interaction detector by use of position-sensitive PMT with a super-bialkali photocathode 査読有り

    Hirano Y, Nitta M, Inadama N, Nishikido F, Yoshida E, Murayama H, Yamaya T

    Radiol. Phys. Technol   7 巻   頁: 57-66   2014年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1007/s12194-013-0231-4

  36. Positron annihilation spectroscopy of biological tissue in 11C irradiation 査読有り

    Sakurai H, Itoh F, Hirano Y, Nitta M, Suzuki K, Kato D, Yoshida E, Nishikido F, Wakizaka H, Kanai T, Yamaya T

    Phys. Med. Biol   59 巻   頁: 7031-8   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  37. Validation of using a 3-dimensional PET scanner during inhalation of 15O-labeld oxygen for quantitative assessment of reginal metabolic rate of oxygen in man 査読有り

    Hori Y, Hirano Y, Koshino K, Moriguchi T, Iguchi S, Yamamoto A, Enmi J, Kawashima H, Zeniya T, Morita N, Nakagawara J, Casey ME, Iida H

    Phys. Med. Biol   59 巻   頁: 5593-609   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  38. X'tal cube PET detector composed of a stack of scintillator plates segmented by laser processing 査読有り

    Inadama N, Moriya T, Hirano Y, Nishikido, F, Murayama H, Yoshida E, Tashima H, Nitta M, Ito H, Yamaya T

    IEEE Trans. Nucl. Sci.   61 巻   頁: 53-59   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  39. Efficient one-pair experimental system for spatial resolution demonstration of prototype PET detectors 査読有り

    Tashima H, Yoshida E, Hirano Y, Nishikido F, Inadama N, Murayama H, Yamaya T

    Radiol. Phys. Technol.   7 巻   頁: 379-86   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  40. Compartmental analysis of washout effect in rat brain: in-beam OpenPET measurement using a 11C beam 査読有り

    Phys. Med. Biol   58 巻   頁: 8281-94   2013年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/0031-9155/58/23/8281

  41. Potential for reducing the numbers of SiPM readout surfaces of laser-processed X'tal cube PET detectors 査読有り

    Hirano Y, Inadama N, Yoshida E, Nishikido F, Murayama H, Watanabe M, Yamaya T

    Phys. Med. Biol.   58 巻   頁: 361-74   2013年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/0031-9155/58/5/1361

  42. Rapid quantitative CBF and CMRO2 measurements from a single PET scan with sequential administration of dual 15O-labeled tracers 査読有り

    Kudomi N, Hirano Y, Koshino K, Hayashi T, Watabe H, Fukushima H, Moriwaki H, Teramoto N, Iihara K and Iida H

    J. Cerb. Blood Flow Metab.   33 巻   頁: 440-8   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  43. The X'tal cube PET detector with a monolithic crystal processed by the 3D sub-surface laser engraving technique: Performance comparison with glued crystal elements 招待有り 査読有り

    Yohida E, Hirano Y, Tashima, H, Inadama N, Nishikid 3F, Moriya T, Omura T, Watanabe M, Murayama H, Yamaya T

    Ncul. Instrum. Methods. Phys Res. A   723 巻   頁: 83-88   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  44. Spatial resolution limits for the isotropic-3D PET detector X'tal cube 査読有り

    Yoshida E, Tashima H, Hirano Y, Inadama N, Nishikido F, Murayama H, Yamaya T

    Ncul. Instrum. Methods. Phys Res., A   728 巻   頁: 107-111   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  45. Development of a single-ring OpenPET prototype 査読有り

    Yoshida E, Tashima, H, Wakizaka H, Nishikido F, Hirano Y, Inadama N, Murayama H, Ito H, Yamaya T

    Ncul. Instrum. Methods. Phys Res. A   729 巻   頁: 800-808   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  46. The X'tal cube PET detector with a monolithic crystal processed by the 3D sub-surface laser engraving technique: Performance comparison with glued 査読有り

    Yoshida E, Hirano Y, Tashima H, Inadama N, Nishikido F, Moriya, T, Omura T, Watanabe M, Murayama H, Yamaya T

    Ncul. Instrum. Methods. Phys Res., A   723 巻   頁: 83–88   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  47. A proposal for PET/MRI attenuation correction with mu-values measured using a fixed-position radiation source and MRI segmentation 査読有り

    Kawaguchi H, Hirano Y, Yoshida E, Jeff K, Suga M, Ikoma Y, Obata T, Ito H, Yamaya T,

    Ncul. Instrum. Methods. Phys Res. A   734 巻   頁: 156-61   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  48. Feasibility Study of an Axially Extendable Multiplex Cylinder PET 査読有り

    Yoshida E, Hirano Y, Tashima H, Inadama N, Nishikido, F, Murayama H., Ito H, Yamaya, T

    IEEE Trans. Nucl. Sci   50 巻   頁: 3227-34   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  49. Impact of Laser-Processed X'tal Cube Detectors on PET Imaging in a One-Pair Prototype System. 査読有り

    Yoshida E, Hirano Y, Tashima H, Inadama N, Nishikido F, Moriya T, Omura T, Watanabe M, Murayama H, Yamaya T

    IEEE Trans. Nucl. Sci.   60 巻   頁: 3172-80   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  50. Monte Carlo estimation of scatter effects on quantitative myocardial blood flow and perfusable tissue fraction using 3D-PET and 15O-water. 査読有り

    Hirano Y, Koshino K, Watabe H, Fukushima K, Iida H

    Phys. Med. Boil   57 巻   頁: 7481-92   2012年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/0031-9155/57/22/7481

  51. Monte Carlo simulation of scintillation photons for the design of a high-resolution SPECT detector dedicated to human brain 査読有り

    Hirano Y, Zeniya T, Iida H

    Ann. Nucl. Med.   26 巻   頁: 214-21   2012年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1007/s12149-011-0561-4

  52. Effects of patient movement on measurements of myocardial blood flow and viability in resting 15O-water PET studies 査読有り

    Koshino K, Watabe H, Enmi J, Hirano Y, Zeniya T, Hasegawa S, Hayashi T, Miyagawa S, Sawa Y, Hatazawa J, Iida H

    J Nucl Cardiol.   19 巻   頁: 524-78   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  53. Experimental pig model of old myocardial infarction with long survival leading to chronic left ventricular dysfunction and remodeling as evaluated by PET 査読有り

    Teramoto N, Koshino K, Yokoyama I, Miyagawa S, Zeniya T, Hirano Y, Fukuda H, Enmi J, Sawa Y, Knuuti J, Iida H

    J Nucl Med.   52 巻   頁: 761-8   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  54. Preliminary Experiments on Accelerator-Driven Subcritical Reactor with Pulsed Neutron Generator in Kyoto University Critical Assembly 査読有り

    Cheol Ho PYEON , Yoshiyuki HIRANO , Tsuyoshi MISAWA , Hironobu UNESAKI , Chihiro ICHIHARA , Tomohiko IWASAKI & Seiji SHIROYA

    Journal of Nuclear Science and Technology   44 巻 ( 11 ) 頁: 1368-1378   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: https://doi.org/10.1080/18811248.2007.9711384

▼全件表示

科研費 10

  1. 4D-Flowと深層学習を用いた脳動脈瘤高分解能血流動態バイオマーカー計算法開発

    研究課題/研究課題番号:21K09175  2021年4月 - 2024年3月

    科学研究費助成事業  基盤研究(C)

    礒田 治夫, 平野 祥之

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    担当区分:研究分担者 

    血流動態(壁剪断応力など)が血管病変発生・成長に大きな役割を担い、脳動脈瘤の発生・成長・破裂のリスクを予測するバイオマーカーになり得る。磁気共鳴流体解析 (MRFD)はヒトから直接データを収集できる利点はあるが、空間分解能と時間分解能が低い。一方、計算流体解析 (CFD)は高時間分解能・高空間分解能であるが、処理時間や計算時間が掛かる欠点があり、臨床応用しにくい。そこで、磁気共鳴画像データを入力データ、CFDの結果を正解データとする教師データを学習させ、臨床現場で直ちにCFDと同等の血流解析結果(バイオマーカーの数値も含め)が得られる「深層学習を用いた人工知能のモデル」を構築することを目指す。

  2. 超並列計算による高線量率超短時間照射 (FLASH) 効果の数理モデルの構築

    研究課題/研究課題番号:21K12246  2021年4月 - 2024年3月

    科学研究費助成事業  基盤研究(C)

    岡田 勝吾, 平野 祥之, 楠本 多聞

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    担当区分:研究分担者 

    近年放射線治療分野では、高線量率超短時間照射(FLASH)の実験研究が精力的に行われている。FLASHは、がん細胞への殺傷能力を維持し、正常細胞への放射線影響を顕著に低減する。実験研究から、正常細胞内で起きる酸素欠乏がFLASH効果の一因とする仮説が提唱されている。本研究では、FLASHにおける酸素の化学反応過程を定量化する数理モデルを構築する。細胞内部の放射線現象をモンテカルロ法でシミュレートして、照射荷電粒子の物理反応と活性酸素種等の化学反応を追跡し、細胞の放射線影響を予測する。FLASHの生物学的効果の定量的評価や、FLASH効果の原理解明等のためのシミュレーション基盤の確立を目指す。

  3. 放射線DNA損傷を制御する酸素分圧機構の計算モデル構築

    研究課題/研究課題番号:21K12116  2021年4月 - 2024年3月

    科学研究費助成事業  基盤研究(C)

    阿蘇 司, 原 正憲, 平野 祥之, 藤原 進

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    担当区分:研究分担者 

    福島原発事故の処理水に含まれるトリチウムが、生態へ与える影響は社会的な関心事である。トリチウムが放出する低エネルギーβ線によるDNA損傷は、放射線の直接作用とともに、放射化学により生じたラジカルが起こす間接作用が影響している。この間接作用は、高酸素下で影響が大きくなり、酸素効果として知られている。本研究では、放射線によるDNA損傷のメカニズムを物理化学的視点から解明することを目標に、間接作用に焦点を当てて、ラジカル発生とその時間変化、更には酸素濃度の効果の寄与を組み込んだモンテカルロ法シミュレーションを開発する。そして、計算結果から、酸素濃度とDNA損傷の関係を評価することを目的とする。

  4. 各種細胞株の放射線照射による生存率曲線と遺伝子発現量の測定

    研究課題/研究課題番号:21K07617  2021年4月 - 2024年3月

    科学研究費助成事業  基盤研究(C)

    平野 祥之, 松井 佑介

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    担当区分:研究代表者 

    配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

    放射線治療において、局所制御率や正常組織の有害事象を予測することは極めて重要である。そのための生物効果モデルが幾つか提案されているが、限られた細胞株でしか検証されていない。またほとんどがLET (linear energy transfer)等の物理量を基に作成されている。そこで本研究では、放射線治療適用部位を起源とする細胞株を中心に、多くの細胞株の細胞生存率曲線と、生物学的な量として、照射後の遺伝子発現情報を取得する。これらのデータベースを作成し、遺伝子発現量と細胞生存率曲線との関係を明らかにするとともに、得られた知見からより高精度な生物効果モデルの作成を試みる。

  5. 放射線誘発DNA二本鎖切断の修復過程における低酸素の影響

    研究課題/研究課題番号:19K08215  2019年4月 - 2022年3月

    科学研究費助成事業  基盤研究(C)

    平山 亮一, 平野 祥之

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    担当区分:研究分担者 

    がん組織には抗がん剤や放射線が効きにくいとされる低酸素領域が存在し、この低酸素がん細胞の根絶が、がん治療では重要となる。研究代表者は、低酸素がん細胞に対する放射線作用を調べ、放射線によるDNAへの直接的なエネルギー付与が細胞を致死へと誘導するのに重要であり、低酸素がん細胞においても有効な作用であることを示した。しかし、がん組織内の低酸素細胞は、放射線照射後も一定期間は低酸素状態にあり、放射線の影響が低酸素状態でどのような修飾を受けるのかは明確になっていない。本研究では、低酸素環境下での放射線に対する生物応答を明らかにするため、放射線誘発DNA損傷の修復過程における低酸素の影響を明らかにする。
    がん組織には抗がん剤や放射線が効きにくいとされる低酸素領域が存在し、この低酸素がん細胞の根絶が、放射線によるがん治療では重要となる。がん組織内の低酸素細胞は、放射線照射後も一定の期間は低酸素状態にあり、放射線によるDNA-DSB(double-strand break)がその低酸素状態でどのような修飾を受けるのかは明確になっていない。2020年度(2年目)は、放射線誘発DNA損傷の修復過程における低酸素の影響を明らかにするため、低LET放射線のX線のデータの加え、炭素線、シリコン線、アルゴン線ならびに鉄線を用いて14~200 keV/micrometreの範囲内でのLET依存性を調べた。実験はチャイニーズハムスター卵巣由来のCHO細胞を用いて行われた。DNA-DSBは定電圧電気泳動法にて定量した。低酸素環境中における酸素濃度は0.04%以下であり、無酸素状態で照射や修復を行った。X線誘発DSBに対する低酸素環境下での修復は大気下での修復よりも効率が悪いことが昨年度までに明らかになっていたが、炭素線、シリコン線、アルゴン線でも同様な結果を示した。鉄線(LET=200)においては100Gy照射のみで有意差が確認できたが、それよりも少ない線量域では修復時の酸素濃度の有無による違いは確認できなかった。最終年度である2021年度では重粒子線のデータを追加し、統計的な評価を行う。また他のエンドポイント(微小核形成など)やDNA修復欠損細胞での実験を行う予定である。
    本研究課題は3年間を予定しており、2年目ではX線のデータに加え、複数の重粒子線誘発DSB修復に対する低酸素影響を調べることができた。計画は問題なく遂行され、予定通り実験データを取得することができたため、次年度では統計的に必要な追加実験を行う予定である。さらに、予定していた微小核形成における低酸素影響を調べる実験は現在解析中であるため、結果については次年度に報告する。
    2021年度は本研究計画の最終年度にあたり、これまでのDSB実験、微小核形成実験を継続し、統計的に十分な実験データを取得する予定である。また、CHOを親株とするxrs6細胞(NHEJ修復遺伝子変異株)と51D1細胞(HR修復遺伝子変異株)を用いて、CHO細胞同様にX線誘発DSB修復に対する低酸素影響を調べ、DSB修復経路と低酸素影響の関連性を明らかにする予定である。

  6. ニューラルネットワークを用いたPET分子イメージングの新しい薬物動態解析

    研究課題/研究課題番号:18K12073  2018年4月 - 2022年3月

    科学研究費助成事業  基盤研究(C)

    越野 一博, 平野 祥之

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    担当区分:研究分担者 

    本研究の目的は、ニューラルネットワークを持つ機械学習を用いて、PET(陽電子断層撮影)・時空間4次元データに対する新たな薬物動態解析法を構築することである。薬物動態解析の目的は、定量的画像診断を行うことにある。着目する病態観察に適した放射性薬剤を被検者に投与し、生体由来信号(体内での放射能濃度の空間的・時間的分布)から、非侵襲的に病態を定量する手法である。
    PET画像には、放射性同位元素の崩壊に起因する統計ノイズが含まれる。これが、PET画像における誤差の本質的な原因であり、特に投与放射能量が低いときにその影響は支配的になる。ノイズを除去し、正確なPET画像を提供することは画像診断精度の向上に貢献する。
    令和2年度に予定していた主な研究項目は、1) 2つの時系列データ(動脈血中および組織に関する時間放射能濃度曲線)を入力として薬物動態パラメータを推定するニューラルネットワークの構築、2) 既存推定手法との比較による性能評価、であった。項目1)の成果は、ニューラルネットワークを用いての薬物動態解析は可能か、という問いに対する答えとなる。項目2)の成果は、パラメータの推定精度において、数理統計学に基づく既存推定手法と比較して、ニューラルネットワークに基づく手法には、「学習」というコストを払うだけの優位性があるのか、という問いに対する答えとなるものである。しかしながら、「現在までの進捗状況」に記載した事由により遅れが生じた。
    申請者は大学教員として勤務している。新型コロナウイルスの感染防止のため、大学での授業が遠隔授業主体となった。それに対応するべく授業資料の準備に多大な時間を要した。そのため、令和2年度の研究計画について遅れが生じた。
    令和2年度に予定していた以下の2点を重点的に遂行する。
    1) 画像診断に重要な指標である薬物動態パラメータ推定のためのニューラルネットワークの性能評価を行う。同一投与放射能量の条件下で、薬物動態パラメータの推定精度を既存解析手法と比較する。
    2) 内部被ばく量を指標とする本手法の性能評価を行う。既存解析法と本手法による
    推定精度が同等になる投与放射能量を定める。投与放射能量を内部被ばく線量へ換算し、放射線防護の観点からも本手法の有用性を示す。
    補助事業延長申請が承認されたため、令和3年度に進捗の遅れを取り戻し、研究を完了する。

  7. 量子化学/分子動力学計算によるDNA損傷の分子解離確率論的計算モデルの構築

    研究課題/研究課題番号:18K11650  2018年4月 - 2022年3月

    科学研究費助成事業  基盤研究(C)

    阿蘇 司, 原 正憲, 藤原 進, 平野 祥之

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    担当区分:研究分担者 

    本研究は、量子化学・分子動力学計算による知見を組み込んだDNA損傷の確率的計算モデル開発を目的としている。今年度は、(1)開発シミュレーションソフトウェアでの間接作用の影響を評価するためのラジカル発生と、その拡散・再結合相互作用の評価、(2)空間クラスタリング法を用いたDNA損傷の確率モデル検証、(3) 分子動力学計算を用いたDNA分子置換に起因する分子構造変化の影響評価、(4)ガンマ線照射による重水中DNA分子の水素置換評価実験を解析するための量子科学計算の導入を実施した。以下に概要を示す。
    (1) 間接作用では、ラジカル発生からその拡散・再結合を追跡して時間的な空間分布を計算してDNA分子の空間形状との対応によりDNA損傷の有無を判断する。計算アルゴリズムは試作したが、計算時間が長く精密な計算を行うことが容易ではないことがわかった。現在、文献調査等を通じてアルゴリズムの改良に着手している。
    (2) 空間スラスタリング法を利用して、直接作用と間接作用の両方を考慮したDNA損傷が評価できる状況にある。このソフトウェアを用いて、多様な条件でのシミュレーションを行なっている。また、(1)のシミュレーション開発のアルゴリズム改良に際しての参考に用いている。
    (3) DNA分子置換が生じた後に、DNA損傷に至る過程を分子動力学計算で評価を行なっている。また、トリチウム水の水分子がDNA分子構造にアクセスする様子を調べるために、水分子とDNA分子構造を入力した分子動力学計算によって、確率的なアクセス頻度を計算できる状況となっている。
    (4) 重水へのガンマ線照射により、DNA分子構造の水素が重水素に置換する可能性を調査している。ガンマ線照射実験で得られた赤外線吸収スペクトルを量子化学計算により解析して、置換反応の有無を評価している。
    多様な計算方法を取り入れつつ、測定実験の試みも取り入れながら全体的な研究活動が進められている。コロナ禍の影響で、研究組織の議論や学会発表等による外部の意見を取り入れる機会が減少してしまったため、研究のまとめと総括の観点では進展が滞ったところがある。しかしながら、各担当の研究者によるそれぞれの研究結果が得られており、研究課題の進捗状況は、概ね順調に進展していると判断している。
    これまでの研究成果を取りまとめて、研究の総括を行うとともに、最終的な成果実績として学会発表等を行なっていく予定である。また、本研究課題の成果を基盤にした、新たな研究課題の発掘と展開に関する議論を開始しており、本研究課題のまとめとともに、更に次の研究課題設定への発展的成果に結びつけることができるように研究総括を行う予定である。

  8. 放射線照射による生体分子の損傷解析と放射線治療効果モデルへの応用

    研究課題/研究課題番号:18K07631  2018年4月 - 2022年3月

    科学研究費助成事業  基盤研究(C)

    平野 祥之, 余語 克紀

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    担当区分:研究代表者 

    配分額:4420000円 ( 直接経費:3400000円 、 間接経費:1020000円 )

    DNA溶液およびアデニン、グアニン、シトシン、チミン、ウラシルをCo60のガンマ線で3kGy照射した。その後、励起波長532nmのラマン分光装置を用いて、非照射と照射DNAおよび塩基サンプルのラマンスペクトルを観測し、先行研究と同様な傾向が見られた。また785nmの励起波長でもラマンスペクトルを測定し、同様な結果が得られることを確認した。例えば1576 cm-1は照射により減少しているが、これはプリンのC4=C5、C4=N3の伸縮振動であり、塩基対のunstackingが原因と考えられている。また1485 cm-1の減少とバンドの広がりは、グアニンのRing mode N7に帰属し、オキソグアニンの生成による減少と考えられている。またラマンスペクトルの解析手法についても、Goldindecによるベースライン補正や、Savitzgy-Golayによるスムージングを導入し、より洗練された解析を実施できるようにした。塩基の照射実験については、照射によりいくつかのピークの変動が確認された。ピークに帰属する振動を特定するために量子化学計算ツールであるGAMESSを用いて、ラマンスペクトルを計算した。計算結果と実験結果でおおむね一致しており、計算結果からピークに帰属する振動を特定できた。これにより放射線の照射によるDNAや塩基がどのように損傷したかが推測できる。本実験で、ラマン分光は、放射線照射によるDNA損傷の推定に有用であることが確認でき、今後は、粒子線や、線エネルギー付与を変えた場合、照射時の酸素濃度の変化、直接作用と間接作用の違いよるラマンスペクトルの変化について、系統的に調べる予定である。
    今年度は、新型コロナウイルス感染拡大防止のため、実験施設が閉鎖あるいは制限されており、実験が予定通り実施できなかった。放射線照射施設やラマン分光装置は、共同利用施設の装置の利用を計画していたため、この影響は避けられなかった。また実験についても、当初準備したDNAサンプルでは、蛍光が多く見られ、ラマンスペクトルが観測できなかった。蛍光が発生しないDNA溶液の選定や実験手法に決定に少し時間を要した。
    DNAの放射線照射後のラマン分光測定については確立した。よって、系統的に条件を変えて、DNAの損傷の様子を観測する。まず紫外線照射により、紫外線の損傷としてよく知られているピリミジン二量体が観測できるかや、制限酵素で切断することで、粘着末端や平滑末端の様子が観測できるかを調べる。これらの結果はDNAの放射線損傷ラマンスペクトルの理解の助けになる。その後、粒子線とX線による損傷スペクトルの変化、粒子線のLETを変化させた場合や酸素濃度の違いによるスペクトルの変化を観測する。一方で量子化学計算によるラマンスピークに帰属する振動を特定することで、より損傷構造の理解が進むことが期待できる。放射線の種類やエネルギー等の条件変化によるDNAの損傷の違いは、その後の修復や細胞の生死に影響があると予想できるため、放射線治療効果予測モデルの構築に有用な情報となると考えている。

  9. 粒子線治療における系統的な線質測定と生物学的効果の推定精度に関する研究

    研究課題/研究課題番号:15K08690  2015年4月 - 2018年3月

    平野 祥之

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    担当区分:研究代表者 

    配分額:4940000円 ( 直接経費:3800000円 、 間接経費:1140000円 )

    炭素線治療における線質と生物学的効果(生存率)の精度の検証を目的として、下記のことを行った。細胞照射とコロニーアッセイ法による生存率を算出するために、自動でコロニー数と大きさを計測するシステムを構築し、安定して生存率を計算できるようにした。このとき細胞の照射条件(線質や二次粒子含有量等)はシミュレーションによって明確にした。シミュレーションはCR39検出器による実験との比較により妥当性を検証した。また生存率を予測するモデルであるMK(microdosimetric kinetic)モデルを修正し、モデルに柔軟性を持たせ、様々な照射条件でも生存率予測を可能にした。

  10. 超高解像度局所分子機能定量SPECT画質改善のための画像再構成アルゴリズムの開発

    研究課題/研究課題番号:26350558  2014年4月 - 2018年3月

    銭谷 勉

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    担当区分:連携研究者 

    本研究では、局所領域分子機能定量可能なピンホールSPECTシステムの実用化を目指して、画像歪、定量性、解像度の改善を目的とした。まず、本システムのために開発した高精細光電子増倍管とフルデジタル回路から構成された検出器は、ノイズ抑制効果が有り、高い固有空間分解能を実現、画像歪が無いことが確認された。また、ピンホールSPECT画像再構成においてガンマ線の被写体内での吸収と散乱線の影響を補正することによって定量性が改善された。さらに、コリメータ開口によるぼけの影響を補正することによって解像度を改善することができた。本研究によって、撮像システムの実用化が進んだ。

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担当経験のある科目 (本学) 8

  1. 医用機器工学1

    2020

  2. 医用機器工学2

    2020

  3. 医用機器工学3

    2020

  4. 医用機器工学実験

    2020

  5. 医用機器工学演習

    2020

  6. 基礎医学物理学実習

    2020

  7. 放射線システム工学特論

    2020

  8. 医用材料工学

    2019

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担当経験のある科目 (本学以外) 8

  1. 放射線システム工学特論

    名古屋大学)

  2. 基礎医学物理学実習

    名古屋大学)

  3. 医用機器工学演習

    名古屋大学)

  4. 医用機器工学実験

    名古屋大学)

  5. 医用機器工学3

    名古屋大学)

  6. 医用機器工学2

    名古屋大学)

  7. 医用機器工学1

    名古屋大学)

  8. 医用材料工学

    名古屋大学)

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