Updated on 2021/10/19

写真a

 
HIRANO Yoshiyuki
 
Organization
Graduate School of Medicine Associate professor
Graduate School
Graduate School of Medicine
Undergraduate School
School of Health Sciences
Title
Associate professor
Contact information
メールアドレス

Degree 1

  1. 博士(理学) ( 2008.6   大阪大学 ) 

Research Areas 3

  1. Others / Others  / 放射線科学

  2. Others / Others  / 医学物理学

  3. Life Science / Radiological sciences

Research History 10

  1. Nagoya University   Graduate School of Medicine   Associate professor

    2020.4

  2. Nagoya University   Graduate School of Medicine Department of Radiological and Medical Laboratory Sciences Radiological Sciences   Associate professor

    2017.9 - 2020.3

  3. Gunma University   Assistant Professor

    2014.11 - 2017.9

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    Country:Japan

  4. Gunma University   Assistant Professor

    2014.11 - 2017.9

  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

    2014.11 - 2017.9

  6. Chiba Institute of Technology

    2012.9 - 2014.3

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    Country:Japan

  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

    2011.7 - 2014.10

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    Country:Japan

  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

    2011.5 - 2011.6

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    Country:Japan

  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

    2010.7 - 2011.4

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    Country:Japan

  10. 国立循環器病研究センター   放射線医学部   流動研究員

    2008.4 - 2010.6

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    Country:Japan

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Education 2

  1. Osaka University   Graduate School, Division of Natural Science

    - 2008.3

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    Country: Japan

  2. Osaka University   Graduate School, Division of Natural Science

    - 2008.3

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    Country: Japan

Professional Memberships 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

Awards 1

  1. IOP Publishing Outstanding Reviewer award

    2020.3  

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    Award type:Honored in official journal of a scientific society, scientific journal 

 

Papers 53

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

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

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   Vol. 1015   2021.11

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    Language:Japanese   Publisher: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

    Scopus

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

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

    JOURNAL OF INSTRUMENTATION   Vol. 16 ( 8 )   2021.8

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    Language:Japanese   Publisher: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

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  3. 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   Vol. 103 ( 9 )   2021.5

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    Language:Japanese   Publisher: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

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  4. 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   Vol. 16 ( 3 )   2021.3

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    Language:Japanese   Publisher: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

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  5. 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   Vol. 21 ( 4 ) page: 1 - 21   2021.2

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    Language:Japanese   Publisher: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

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  6. 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   Vol. 96 ( 2 )   2021.2

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    Language:Japanese   Publisher: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

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  7. Imaging of polarized components of Cerenkov light and luminescence of water during carbon-ion irradiation

    Yamamoto Seiichi, Yabe Takuya, Akagi Takashi, Hirano Yoshiyuki

    MEDICAL PHYSICS   Vol. 48 ( 1 ) page: 427 - 433   2021.1

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    Language:Japanese   Publisher: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

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  8. Optical imaging of muons

    Yamamoto Seiichi, Ninomiya Kazuhiko, Kawamura Naritoshi, Hirano Yoshiyuki

    SCIENTIFIC REPORTS   Vol. 10 ( 1 ) page: 20790   2020.12

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    Language:Japanese   Publisher: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

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  9. 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   Vol. 108 ( 3 ) page: E254 - E254   2020.11

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    Language:Japanese  

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  10. 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   Vol. 1662 ( 1 )   2020.10

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    Language:Japanese   Publisher: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

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  11. 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   Vol. 6 ( 4 ) page: 045002   2020.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1088/2057-1976/ab8b7e

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  12. 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   Vol. 4 ( 7 )   2020.7

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    Publisher:Journal of Physics Communications  

    DOI: 10.1088/2399-6528/ab9f8d

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

    Yamamoto S

    Radiation Measurements   Vol. 134   2020.6

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.radmeas.2020.106368

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

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

    Physics in medicine and biology   Vol. 65 ( 10 ) page: 105011   2020.5

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1088/1361-6560/ab8532

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  15. 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   Vol. 133   2020.4

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.radmeas.2020.106299

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  16. Estimations of relative biological effectiveness of secondary fragments in carbon ion irradiation of water using CR-39 plastic detector and microdosimetric kinetic model Reviewed

    Yoshiyuki Hirano, Satoshi Kodaira, Hikaru Souda, Kohei Osaki, Masami Torikoshi

    Medical Physics   Vol. 47 ( 2 ) page: 781 - 789   2020.2

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    Language:English   Publishing type:Research paper (scientific journal)  

    © 2019 American Association of Physicists in Medicine 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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  17. Estimation of dose and light distributions in water during irradiation of muon beams

    Yoshiyuki Hirano, Kazuhiko Ninomiya, Seiichi Yamamoto

    Physica Scripta   Vol. 94 ( 12 )   2019.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    © 2019 IOP Publishing Ltd. 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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  18. Scintillator screen for measuring dose distribution in scanned carbon-ion therapy Reviewed

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

    Radiation Measurements   Vol. 129   2019.10

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    © 2019 Elsevier Ltd 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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  19. Estimation of the fractions of luminescence of water at higher energy than Cerenkov-light threshold for various types of radiation. International journal

    Yoshiyuki Hirano, Seiichi Yamamoto

    Journal of biomedical optics   Vol. 24 ( 6 ) page: 1 - 9   2019.6

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    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 ∼0.1  %   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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  20. Estimation of the three-dimensional (3D) dose distribution of electron beams from medical linear accelerator (LINAC) using plastic scintillator plate

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

    RADIATION MEASUREMENTS   Vol. 124   page: 103 - 108   2019.5

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    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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  21. 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   Vol. 3 ( 3 ) page: 371 - 376   2019.5

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    DOI: 10.1109/TRPMS.2018.2876410

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

    Hirano Yoshiyuki, Yamamoto Seiichi

    BIOMEDICAL PHYSICS & ENGINEERING EXPRESS   Vol. 5 ( 2 )   2019.2

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    DOI: 10.1088/2057-1976/ab05b0

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  23. 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   Vol. 63 ( 18 ) page: 185006   2018.9

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    DOI: 10.1088/1361-6560/aadaa6

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

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

    Physics in Medicine and Biology   Vol. 63 ( 12 ) page: 125019   2018.6

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    © 2018 Institute of Physics and Engineering in Medicine. 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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  25. Washout effect in rabbit brain: In-beam PET measurements using 10C, 11C and 15O ion beams

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

    Biomedical Physics and Engineering Express   Vol. 4 ( 3 )   2018.5

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

    Sung Hyun Lee, Naoki Sunaguchi, Yoshiyuki Hirano, Yosuke Kano, Chang Liu, Masami Torikoshi, Tatsuya Ohno, Takashi Nakano, Tatsuaki Kanai

    Physics in Medicine and Biology   Vol. 63 ( 3 ) page: 035025   2018.1

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    In this study, we investigate the performance of the Gunma University Heavy Ion Medical Center's ion computed tomography (CT) system, which measures the residual range of a carbon-ion beam using a fluoroscopy screen, a charge-coupled-device camera, and a moving wedge absorber and collects CT reconstruction images from each projection angle. Each 2D image was obtained by changing the polymethyl methacrylate (PMMA) thickness, such that all images for one projection could be expressed as the depth distribution in PMMA. The residual range as a function of PMMA depth was related to the range in water through a calibration factor, which was determined by comparing the PMMA-equivalent thickness measured by the ion CT system to the water-equivalent thickness measured by a water column. Aluminium, graphite, PMMA, and five biological phantoms were placed in a sample holder, and the residual range for each was quantified simultaneously. A novel method of CT reconstruction to correct for the angular deflection of incident carbon ions in the heterogeneous region utilising the Bragg peak reduction (BPR) is also introduced in this paper, and its performance is compared with other methods present in the literature such as the decomposition and differential methods. Stopping power ratio values derived with the BPR method from carbon-ion CT images matched closely with the true water-equivalent length values obtained from the validation slab experiment.

    DOI: 10.1088/1361-6560/aaa453

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  27. 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   Vol. 28 ( 2 ) page: 221 - 226   2018

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    DOI: 10.1080/14397595.2017.1332558

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  28. Influences of 3D PET scanner components on increased scatter evaluated by a Monte Carlo simulation Reviewed

    Yoshiyuki Hirano, Kazuhiro Koshino, Hidehiro Iida

    PHYSICS IN MEDICINE AND BIOLOGY   Vol. 62 ( 10 ) page: 4017 - 4030   2017.5

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    Monte Carlo simulation is widely applied to evaluate the performance of three-dimensional positron emission tomography (3D-PET). For accurate scatter simulations, all components that generate scatter need to be taken into account. The aim of this work was to identify the components that influence scatter. The simulated geometries of a PET scanner were: a precisely reproduced configuration including all of the components; a configuration with the bed, the tunnel and shields; a configuration with the bed and shields; and the simplest geometry with only the bed. We measured and simulated the scatter fraction using two different set-ups: (1) as prescribed by NEMA-NU 2007 and (2) a similar set-up but with a shorter line source, so that all activity was contained only inside the field-of-view (FOV), in order to reduce influences of components outside the FOV. The scatter fractions for the two experimental set-ups were, respectively, 45% and 38%. Regarding the geometrical configurations, the former two configurations gave simulation results in good agreement with the experimental results, but simulation results of the simplest geometry were significantly different at the edge of the FOV. From the simulation of the precise configuration, the object (scatter phantom) was the source of more than 90% of the scatter. This was also confirmed by visualization of photon trajectories. Then, the bed and the tunnel were mainly the sources of the rest of the scatter. From the simulation results, we concluded that the precise construction was not needed; the shields, the tunnel, the bed and the object were sufficient for accurate scatter simulations.

    DOI: 10.1088/1361-6560/aa6644

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  29. Induced radioactivity of a GSO scintillator by secondary fragments in carbon ion therapy and its effects on in-beam OpenPET imaging Reviewed

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

      Vol. 61   page: 4870-89   2016

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

  30. Development of a DOI PET Detector Having the Structure of the X'tal Cube Extended in One Direction Reviewed

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

    IEEE Trans. On Nucl. Science   Vol. 63   page: 2509-16   2016

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

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

    Phys. Med. Biol   Vol. 61   page: 1875-87   2016

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    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 Reviewed

    Hirano Y, Nishikido F, Kokuryo D, Yamaya T

    Radiol. Phys. Technol.   Vol. 9   page: 245-53   2016

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    DOI: 10.1007/s12194-016-0356-3

  33. Monte Carlo simulation of small OpenPET prototype with 11C beam irradiation: effects of secondary particles on in-beam imaging Reviewed

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

    Phys. Med. Biol.   Vol. 59   page: 1623-40   2014

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

  34. Efficient one-pair experimental system for spatial resolution demonstration of prototype PET detectors Reviewed

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

    Radiol. Phys. Technol.   Vol. 7   page: 379-86   2014

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  35. Positron annihilation spectroscopy of biological tissue in 11C irradiation Reviewed

    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   Vol. 59   page: 7031-8   2014

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  36. Performance evaluation of a depth-of-interaction detector by use of position-sensitive PMT with a super-bialkali photocathode Reviewed

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

    Radiol. Phys. Technol   Vol. 7   page: 57-66   2014

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    DOI: 10.1007/s12194-013-0231-4

  37. X'tal cube PET detector composed of a stack of scintillator plates segmented by laser processing Reviewed

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

    IEEE Trans. Nucl. Sci.   Vol. 61   page: 53-59   2014

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  38. 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 Reviewed

    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   Vol. 59   page: 5593-609   2014

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  39. Compartmental analysis of washout effect in rat brain: in-beam OpenPET measurement using a 11C beam Reviewed

    Phys. Med. Biol   Vol. 58   page: 8281-94   2013

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

  40. Potential for reducing the numbers of SiPM readout surfaces of laser-processed X'tal cube PET detectors Reviewed

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

    Phys. Med. Biol.   Vol. 58   page: 361-74   2013

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

  41. Rapid quantitative CBF and CMRO2 measurements from a single PET scan with sequential administration of dual 15O-labeled tracers Reviewed

    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.   Vol. 33   page: 440-8   2013

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  42. 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 Invited Reviewed

    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   Vol. 723   page: 83-88   2013

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  43. Spatial resolution limits for the isotropic-3D PET detector X'tal cube Reviewed

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

    Ncul. Instrum. Methods. Phys Res., A   Vol. 728   page: 107-111   2013

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  44. Development of a single-ring OpenPET prototype Reviewed

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

    Ncul. Instrum. Methods. Phys Res. A   Vol. 729   page: 800-808   2013

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

    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   Vol. 723   page: 83–88   2013

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  46. A proposal for PET/MRI attenuation correction with mu-values measured using a fixed-position radiation source and MRI segmentation Reviewed

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

    Ncul. Instrum. Methods. Phys Res. A   Vol. 734   page: 156-61   2013

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  47. Feasibility Study of an Axially Extendable Multiplex Cylinder PET Reviewed

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

    IEEE Trans. Nucl. Sci   Vol. 50   page: 3227-34   2013

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  48. Impact of Laser-Processed X'tal Cube Detectors on PET Imaging in a One-Pair Prototype System. Reviewed

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

    IEEE Trans. Nucl. Sci.   Vol. 60   page: 3172-80   2013

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  49. Monte Carlo simulation of scintillation photons for the design of a high-resolution SPECT detector dedicated to human brain Reviewed

    Hirano Y, Zeniya T, Iida H

    Ann. Nucl. Med.   Vol. 26   page: 214-21   2012

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    DOI: 10.1007/s12149-011-0561-4

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

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

    Phys. Med. Boil   Vol. 57   page: 7481-92   2012

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

  51. Effects of patient movement on measurements of myocardial blood flow and viability in resting 15O-water PET studies Reviewed

    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.   Vol. 19   page: 524-78   2011

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  52. Experimental pig model of old myocardial infarction with long survival leading to chronic left ventricular dysfunction and remodeling as evaluated by PET Reviewed

    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.   Vol. 52   page: 761-8   2011

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  53. Preliminary Experiments on Accelerator-Driven Subcritical Reactor with Pulsed Neutron Generator in Kyoto University Critical Assembly Reviewed

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

    Journal of Nuclear Science and Technology   Vol. 44 ( 11 ) page: 1368-1378   2007

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

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KAKENHI (Grants-in-Aid for Scientific Research) 10

  1. 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

    Grant number:21K12246  2021.4 - 2024.3

    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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    Authorship:Coinvestigator(s) 

    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。

  2. 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

    Grant number:21K12116  2021.4 - 2024.3

    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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    Authorship:Coinvestigator(s) 

    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。

  3. 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

    Grant number:21K07617  2021.4 - 2024.3

    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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    Authorship:Principal investigator 

    Grant amount:\4160000 ( Direct Cost: \3200000 、 Indirect Cost:\960000 )

    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。

  4. Development of high-resolution hemodynamic biomarker calculation method for cerebral aneurysms using 4D-Flow and deep learning

    Grant number:21K09175  2021.4 - 2024.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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  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

    Grant number:19K08215  2019.4 - 2022.3

    平山 亮一

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    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。2019年度(1年目)は、低酸素環境下での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し、放射線照射後の酸素環境が細胞の生死とどのような関係にあるかを明らかにするため、1)X線誘発DSBの修復に対する低酸素の影響を調べた予備実験のデータを補強し、2)高LET放射線である鉄線(200 keV/micrometre)誘発DSBの修復に対する低酸素の影響を調べた。さらに3)低酸素環境下での微小核形成を行い、染色体異常の誘発頻度における低酸素の影響を予備的に調べた。
    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。DSBは定電圧電気泳動法にて定量した。微小核形成はサイトカラシンBを用いた細胞分裂阻害微小核形成アッセイにより行った。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再確認できた。一方、鉄線誘発DSBに対する修復には酸素の関与はほとんど無いことがわかった。微小核形成においても照射後の低酸素処理により、微小核が大気下よりも多く観察され、照射後の低酸素はDNA修復の効率低下や染色体異常の誘発を引き起こすことが示唆された。翌年度は重粒子線のデータを追加し、統計的な評価を行う。微小核形成実験においても同様に統計的な評価が行えるよう、繰り返し実験を行う予定です。
    本研究は3年間を予定しており、1年目ではX線や重粒子線誘発DSB修復に対する低酸素影響を調べる計画であった。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。さらに、次年度以降を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を予備的に開始でき、一部データも取得できた。重粒子線の実験ついては、マシンタイムの配分が希望回数に満たなかったため、翌年度に実施を継続する。
    2020年度は本研究計画の2年目にあたり、1年目で取得できた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. 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

    Grant number:18K11650  2018.4 - 2021.3

    阿蘇 司

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    本研究は、量子化学・分子動力学計算による知見を組込んだ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、トリチウム水での低エネルギー・ベータ線によるDNA損傷に関して、(1)直接作用によるDNA損傷判定条件についてエネルギー付与閾値と鎖切断(SB)との関係、(2)直接作用と間接作用を考慮した一本鎖切断(SSB)と二本鎖切断(DSB)の比について、それぞれ異なる確率判定モデルを適用した。更に(3)水素の分子置換に関する試行実験に着手した。以下に概要を示す。
    (1)Geant4-DNAによりベータ線の空間エネルギー付与を計算し、DNA原子配列と対応付けて、五炭糖またはリン酸塩基の構成原子の実効体積内に閾値以上のエネルギーが付与された場合にSBが生じると仮定した。エネルギー閾値が高いと、指数関数的にSSB数とDSB数が減少した。他研究でも閾値は未確定であり、測定との比較が望まれる。間接作用については、DNA構成原子とラジカルの分子動力学計算による動体解析を行っており、Geant4-DNAへの計算結果の導入を進めている。
    (2)直接作用、間接作用の両方を考慮したDNA損傷の計算法として、J.C.Fosterらによる空間クラスタリング法を適用した。この計算モデルは五炭糖での反応に加えて、塩基との反応後に五炭糖へラジカル移行が生じる反応の連鎖機構がモデル化されている。本研究では、トリチウム崩壊ベータ線において、SSB/DSB比が原論文と矛盾ない結果が得られることを確認した。
    (3)水中の水素同位体がDNA分子の水素(H)に置換して影響を与える可能性を調査するため、重水素(D)にアミノ酸を溶かした溶液にCo-60のガンマ線を照射して、乾燥後に赤外線吸収スペクトル測定を行った。アミノ酸でHとDの置換が行われたことを確認した。詳細な解析のために分子動力学計算との比較等を予定している。
    研究組織の中で、多様な計算方法並びに実験を取り入れて、それらの活動が有機的に並行して進んでいる。Geant4-DNAによるモンテカルロシミュレーションを基盤として、2つの確率計算モデルでの計算手法開発が進んでおり、相互に結果を比較検討することで新たな知見が得られる可能性が大きい。同時に、分子動力学計算に関する結果や支援を他機関から得られる体制が構築されており、本研究課題を基盤としつつ研究を発展させるための研究体制が整っている。
    得られている成果を、学会や論文等として発表することを検討しており、研究は概ね順調に進展していると判断している。
    これまでの研究により、直接作用での判定条件がDNA損傷の見積もり結果に与える影響を、DNA分子構造を導入したモンテカルロシミュレーションGeant4-DNAを用いて定性的に評価した。並行して評価を行っておる空間クラスタリング法の確率モデルでは、DNA構造は円筒形の模擬的な形状を仮定しているが、判定条件としては間接作用でのラジカル反応確率、DNA分子内でのラジカル移行による損傷確率など、DNA損傷にいたる過程を包括的に考慮している。これら2つの計算モデルは、粒子追跡法に基づき計算するか、簡易形状モデル条件下で確率統計的に計算するかの違いがある。本課題では、前者の粒子追跡法に基づく計算を基礎と考えているため、後者の空間クラスタリングモデルの計算手法を、前者の計算モデルの枠組みに導入することを今後の目標とする。
    同時に、分子動力学計算による結果から、OHラジカルの滞留確率が高いDNA分子内サイトが明らかになっている。OHラジカルによる水素原子の引き抜き、分子のラジカル化、そしてラジカルのDNA分子内移行、鎖切断と複雑な過程をとることが考えられるが、その発端はOHラジカルのDNA分子への接触であり、滞留確率は非常に重要な条件であると考えている。
    今後の予定として、(1)粒子追跡法と空間クラスタリングモデルを統合したシミュレーションの開発、(2)開発コードと空間クラスタリングモデルの比較、(3)OHラジカルのDNA分子への滞留確率を取り入れた評価を行う。

  7. 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

    Grant number:18K07631  2018.4 - 2021.3

    平野 祥之

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    Authorship:Principal investigator 

    Grant amount:\4420000 ( Direct Cost: \3400000 、 Indirect Cost:\1020000 )

    実験については、バイオ実験については専門外であるため、ゼロから環境を整えるのに時間を要したがDNAの電気泳動ができるようになった。研究の目的の一つとしてDNAの損傷をラマンスペクトルで特徴付けることだが、ある程度はすでに研究されており、複数の先行研究により、損傷とラマンスペクトルの関係を見つけることができた。当該研究では、まず切断箇所の様子が明確になっている制限酵素による切断のラマンスペクトルを確認しようと試みたがうまく観測できなかった。おそらく電気泳動で分離した後、該当箇所を取り出す際の手続きに問題があったと考えられる。バイオの専門家に改善策の教示を受ける予定である。またはマイクロチップ電気泳動を利用して分離後、直接分光器で観測する方法を検討している。
    一方シミュレーションについては、DNAの直接効果に加えOHラジカルによる間接効果のモデルを組み込み両方の効果を考慮した。さらに文献を参考にして酸素濃度を考慮したモデルをシミュレーションに取り入れ、DSB/SSB比について文献値とほぼ一致させることができた。これにより粒子種やLETの違いによる損傷具合の予測を調べることができる。しかしこのシミュレーションについても、多くのモデルパラメータがあり、パラメータの値の妥当性について検討しなければならない。平行して分子動力学計算をはじめたので、損傷したDNAがどのような形で安定するのかについて調べる予定である。こちらについては分子動力学の専門家の指導を受けて進めている。
    主に、教育関連の仕事にエフォートの多くを費やしたためである。新しい講義を複数担当することになり、その準備に苦労を要した。また複数人の研究者の研究分担者にもなっておりそれらの研究にも多くの時間を割く必要があった。このように研究と教育および共同研究とのエフォートのバランスが予定していた配分から大きく崩れ、自身の研究以外に尽力することになったことが原因である。
    新規講義の準備は、ほぼ済んだため、教育へのエフォートを計画していた配分に下げ、研究の時間に割り当てる予定である。シミュレーションについては順調に進んでいるので、とにかく実験に重点を置いて進めていきたい。不慣れなバイオ実験を行う機会が多いため、バイオ実験の専門家である機器をお借りしている担当者等のアドバイスを積極的に伺い進めていく。具体的には損傷DNAのラマンスペクトルを観測するために、アガロース電気泳動での分離ではなく、マイクロチップあるいはマイクロキャピラリー電気泳動装置を利用することで、損傷DNAの抽出作業をせず、直接分光器で観測することである。他にも、分光器をお借りしている施設にはNMRも所有しているため、NMRによる損傷の特徴づけについてお検討したい。しかし新型コロナウイルス感染拡大にともなう他施設での実験自粛が研究の進捗に影響しないかが不安要素として残る。

  8. Novel pharmacokinetic analysis for PET molecular imaging based on neural network approach

    Grant number:18K12073  2018.4 - 2021.3

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  9. study on accuracy of biological effects and liner energy transfer in heavy ion therapy

    Grant number:15K08690  2015.4 - 2018.3

    Hirano Yoshiyuki

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    Authorship:Principal investigator 

    Grant amount:\4940000 ( Direct Cost: \3800000 、 Indirect Cost:\1140000 )

    In order to verify the accuracy of liner energy transfer (LET) and biological effect (survival rate) in heavy ion therapy, I conducted experiments and simulations as follows. To calculate the survival rate by cell irradiation and colony assay method, I made an automatic system to count number of colony and measure size of the colony which may suggested dependency of LET distribution on cellular growth. The system enabled us to measure survival rate with stability. The irradiation conditions (LET distribution, secondary particle content etc) of the cell were clarified by simulation. The simulation was verified by comparing with the experimental LET distribution in carbon irradiation with the CR39 detector. I also modified the MK (microdosimetric kinetic) model, which is a model to predict survival rate, giving flexibility to the model and enabling prediction of survival rate under various irradiation conditions.

  10. Development of an image reconstruction algorithm for image improvement of ultra-high spatial resolution SPECT for molecular functional quantitation in a selected small region

    Grant number:26350558  2014.4 - 2018.3

    ZENIYA Tsutomu

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    Authorship:Collaborating Investigator(s) (not designated on Grant-in-Aid) 

    We are developing an ultra-high spatial-resolution pinhole SPECT system to quantify molecular functions in a selected small region. This study aimed to improve distortion, quantitation and spatial resolution of the image generated in this system. First, it was conformed that the used full-digital detector with multiple position-sensitive photomultiplier tubes had high spatial resolution and no image distortion due to noise suppression. Second, the image quantitation was improved by correcting the effects of attenuation and scatter inside the object in pinhole SPECT image reconstruction. Third, the spatial resolution was improved by correcting the effect of the blurring due to collimator aperture. This study promoted the practical use of this SPECT system

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Teaching Experience (On-campus) 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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Teaching Experience (Off-campus) 8

  1. 放射線システム工学特論

    Nagoya University)

  2. 基礎医学物理学実習

    Nagoya University)

  3. 医用機器工学演習

    Nagoya University)

  4. 医用機器工学実験

    Nagoya University)

  5. 医用機器工学3

    Nagoya University)

  6. 医用機器工学2

    Nagoya University)

  7. 医用機器工学1

    Nagoya University)

  8. 医用材料工学

    Nagoya University)

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