Updated on 2024/03/19

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 Interests 3

  1. Radiation simulations

  2. Radiation Measurements

  3. Radiation Effects

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 3

  1. THE JAPANESE RADIATION RESEARCH SOCIETY

    2022.9

  2. 日本医学物理学会

  3. 日本核医学学会

Awards 3

  1. Outstanding Presentation Award

    2023.11   Japan Society for Simulation Technology   An estimation of produced oxygen in the track of heavy-ion using Geant4-DNA

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    Award type:Award from international society, conference, symposium, etc.  Country:Japan

  2. IOP Publishing Outstanding Reviewer award

    2020.3  

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

  3. 菅野賞

    2015.12   核医学画像解析研究会  

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    Award type:Award from Japanese society, conference, symposium, etc. 

 

Papers 62

  1. Discrimination of inter-crystal scattering events by signal processing for the X'tal cube PET detector

    Nitta, M; Nishikido, F; Inadama, N; Hirano, Y; Yamaya, T

    RADIOLOGICAL PHYSICS AND TECHNOLOGY   Vol. 16 ( 4 ) page: 516 - 531   2023.10

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    Language:English   Publisher:Radiological Physics and Technology  

    Inter-crystal scattering (ICS) events cause degradation of the contrast in PET images. We developed the X’tal cube PET detector with submillimeter spatial resolution, which consisted of a segmented LYSO scintillator and 96 MPPCs. For this high spatial resolution PET detector, the ICS event was not negligible. In this study, we proposed a method to discriminate the ICS events and showed its feasibility by the following method. For each 96 MPPC, we measured the mean and standard deviation of the peak in the pulse height distribution obtained by the photoabsorption events in a scintillator pixel. Every time a newly detected event was identified as the segment, we monitored the reduced chi-square value that was calculated with the pulse height and the prepared mean and the standard deviation for each 96 MPPC. Since the pulse height caused by the photoabsorption event resulted in a small reduced chi-square value, we could eliminate the ICS events by setting a threshold on the reduced chi-square value. We carried out both a Monte Carlo simulation and a scanning experiment. By the simulation, we confirmed that the threshold of the reduced chi square significantly discriminated the ICS event. We obtained the response function by a scanning experiment with a 0.2 mm slit beam of 511 keV gamma-ray. The standard deviation of the response function was improved from 1.6 to 1.06 mm by eliminating the ICS events. The proposed method could significantly eliminate the ICS events and retain the true events.

    DOI: 10.1007/s12194-023-00740-3

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  2. Dose distribution measurements using luminol water during irradiation of high-energy X-rays from medical linear accelerators (LINAC)

    Yamamoto, S; Yamada, K; Yabe, T; Hirano, Y; Kataoka, J

    RADIATION PHYSICS AND CHEMISTRY   Vol. 208   2023.7

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    Publisher:Radiation Physics and Chemistry  

    Dose distribution measurements of high-energy X-rays from a medical linear accelerator (LINAC) in water are important for quality control (QC) of the system, and Cherenkov-light imaging is an efficient method for measuring the high-energy X-ray dose distribution. However, the depth profiles have an underestimated dose at increased depths due to the angular dependency of the Cherenkov light. Luminol water is a possible material for measuring the dose distribution by detecting the light emitted from the chemical reaction with the reactive hydroxyl radical (・OH) produced in water by irradiation. In this study, we used luminol water for dose distribution measurements of high-energy X-rays from a LINAC. Imaging of the light emitted from luminol water was conducted using a cooled charge-coupled device (CCD) camera during irradiation with 6 MV X-rays from a LINAC to the luminol water. Imaging of the Cherenkov light in water was also conducted by irradiating 6 MV X-rays to water for correcting the Cerenkov-light component produced in luminol water. The Cherenkov-light image was subtracted from that of the luminol water to derive a dose image. The light emission of luminol water was ∼3 times higher than that of Cherenkov light in water. By subtracting the Cherenkov-light image from the luminol-water image, we could obtain an image that was identical to the dose distributions. The difference in the relative dose distribution was within −0.4% for the corrected image while that of the Cherenkov-light image was −7.9%. The multiple irradiations of luminol water with X-rays produced non-uniformity of emitted light, probably due to the production of hydrogen peroxide (H2O2) in water. We confirmed that imaging luminol water was promising for dose distribution imaging by correcting the Cherenkov-light component in the images. The non-uniformity of the emitted light by multiple irradiations in luminol water needs to be solved for more stable measurements.

    DOI: 10.1016/j.radphyschem.2023.110895

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  3. Cherenkov-light imaging of induced positron distribution in liquid water after proton beam irradiation

    Yamamoto, S; Yamashita, T; Kobashi, Y; Hirano, Y; Akagi, T; Yokokawa, H; Kataoka, J

    JOURNAL OF INSTRUMENTATION   Vol. 17 ( 11 )   2022.11

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    Publisher:Journal of Instrumentation  

    Imaging of positrons induced by nuclear reactions with a proton beam is a possible method for observing the beam shape from outside the subject. However, such imaging of induced positrons has so far been conducted for solid materials. The induced positron distribution in liquid water has not been measured or reported. To clarify the distribution of induced positrons in liquid water, we conducted Cherenkov-light imaging after irradiation by protons to a water phantom. After irradiation by a 117-MeV proton beam to a phantom containing liquid water, Cherenkov-light imaging of the induced positrons was conducted using a cooled charge-coupled device (CCD) camera following the decay of the positrons. We also imaged the luminescence of water during irradiation by the proton beam to compare the distributions. We could measure the distribution of Cherenkov-light from the induced positrons in liquid water. Positron distributions kept their beam shapes in water but were different from that of the luminescence image; positron distribution was wider in the deep area of the beams in the lateral as well as depth direction. The distributions' shapes were only slightly changed with time. We conclude that Cherenkov-light imaging from the induced positrons after irradiation by a proton beam in water was possible, and we found that the induced positrons kept their beam shape in water with different shape from that of dose. These findings may provide new insights for imaging in particle therapy.

    DOI: 10.1088/1748-0221/17/11/P11043

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  4. Imaging of hydroxyl radical (.OH) distributions using luminol water during irradiation with low-energy X-rays

    Yamamoto, S; Yabe, T; Hirano, Y; Kataoka, J

    JOURNAL OF INSTRUMENTATION   Vol. 17 ( 10 )   2022.10

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    Publisher:Journal of Instrumentation  

    Reactive hydroxyl radicals (·OH) play important roles in the biological effects of radiation exposure or radiation therapy, and the distribution of ·OH in water during irradiation is of interest to researchers. However, real-time ·OH distribution measurement during irradiation has so far not been achieved due to the difficulty of detecting ·OH. To make these distribution measurements possible, we attempted the imaging of light emitted from luminol water during irradiation with low-energy X-rays. Imaging of the light emitted from luminol water was conducted using a cooled charge-coupled device (CCD) camera during X-ray irradiation to luminol water at lower energy than the Cherenkov-light threshold. The light emission of luminol water was 25 times higher than that of water, and clear images of light distributions were measured for the luminol water. By carrying out the imaging of luminol water with the addition of a radical scavenger to the luminol water, we could confirm that the emitted light was from ·OH produced in water. With this addition of the radical scavenger, the light intensity decreased as the weight of the scavenger increased. With these results, we confirmed that the detected light distribution in luminol water could be attributed to the ·OH produced by the X-ray irradiation.

    DOI: 10.1088/1748-0221/17/10/T10004

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  5. Technical note: Correcting angular dependencies using non‐polarized components of Cherenkov light in water during high‐energy X‐ray irradiation

    Chihiro Toyonaga, Seiichi Yamamoto, Takuya Yabe, Kuniyasu Okudaira, Katsunori Yogo, Yoshiyuki Hirano, Jun Kataoka

    Medical Physics   Vol. 49 ( 8 ) page: 5409 - 5416   2022.8

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

    DOI: 10.1002/mp.15794

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1002/mp.15794

  6. Measurement of biological washout rates depending on tumor vascular status in <SUP>15</SUP>O in-beam rat-PET

    Toramatsu, C; Mohammadi, A; Wakizaka, H; Sudo, H; Nitta, N; Seki, C; Kanno, I; Takahashi, M; Karasawa, K; Hirano, Y; Yamaya, T

    PHYSICS IN MEDICINE AND BIOLOGY   Vol. 67 ( 12 )   2022.6

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    Language:English   Publisher:Physics in Medicine and Biology  

    Objective. The biological washout of positron emitters should be modeled and corrected in order to achieve quantitative dose range verification in charged particle therapy based on positron emission tomography (PET). This biological washout effect is affected by physiological environmental conditions such as blood perfusion and metabolism, but the correlation to tumour pathology has not been studied yet. Approach. The aim of this study was to investigate the dependence of the biological washout rate on tumour vascular status in rat irradiation. Two types of tumour vascularity conditions, perfused and hypoxic, were modelled with nude rats. The rats were irradiated by a radioactive 15O ion beam and time activity curves were acquired by dynamic in-beam PET measurement. Tumour tissue sections were obtained to observe the histology as well. The biological washout rate was derived using a single-compartment model with two decay components (medium decay, k 2m and slow decay, k 2s ). Main results. All k 2m values in the vascular perfused tumour tissue were higher than the values of the normal tissue. All k 2m values in the hypoxic tumour tissue were much lower than the values of the vascular perfused tumour tissue and slightly lower than the values of the normal tissue. Significance. The dependency of the biological washout on the tumour vasculature conditions was experimentally shown.

    DOI: 10.1088/1361-6560/ac72f3

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  7. Study on the DNA-damage by Tritium using Geant4-DNA simulation

    Aso Tsukasa, Hara Masanori, Hirano Yoshiyuki

    Transactions of Japanese Society for Medical and Biological Engineering   Vol. Annual60 ( Abstract ) page: 257_1 - 257_1   2022

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    Language:English   Publisher:Japanese Society for Medical and Biological Engineering  

    <p>Tritium is an isotope of hydrogen that emits very low energy beta-rays (18.6 keV maximum). The external exposure is limited while ingesting tritium in the body is considered to result in internal exposure. Such radiation damage in living cells is induced through DNA strand breaks (SBs) via direct and indirect effect. In this paper, we adopted the mechanistic approach of SBs by using an atomistic DNA model and a Monte Carlo simulation based on Geant4-DNA. The simulation includes physics interactions of beta-ray in water and subsequent chemical reactions of radicals in water radiolysis. The SB was assumed to occur if an energy was deposited beyond a certain threshold or if a hydroxyl radical approached inside phosphate or sugar sites in DNA-molecules. The results are discussed in the ratio of single strand breaks (SSBs) to double strand breaks (DSBs) with the contributions of direct and indirect effects.</p>

    DOI: 10.11239/jsmbe.annual60.257_1

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  8. 3-D Optical Imaging System of Muon Beams Using a Silver Activated Zinc Sulfide (ZnS(Ag)) Sheet Combined With a Mirror

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

    IEEE TRANSACTIONS ON NUCLEAR SCIENCE   Vol. 68 ( 12 ) page: 2748 - 2752   2021.12

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    Language:Japanese   Publisher: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

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  9. 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 & 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

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  10. 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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  11. Low background measurement in CANDLES-III for studying the neutrinoless double beta decay of <SUP>48</SUP>Ca

    Ajimura, S; Chan, WM; Ichimura, K; Ishikawa, T; Kanagawa, K; Khai, BT; 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, VTT; 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, KK; 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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  12. 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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  13. Calculation of Stopping-Power Ratio from Multiple CT Numbers Using Photon-Counting CT System: Two- and Three-Parameter-Fitting Method

    Lee, SH; Sunaguchi, N; Nagao, A; Hirano, Y; Sakurai, H; Kano, Y; Torikoshi, M; Kanai, T; Tashiro, M

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

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    Language:English   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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  14. Position distribution calculation of annihilation radiations and bremsstrahlung x rays in water during irradiation of positive muons: a Monte Carlo simulation study

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

    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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  15. Imaging of polarized components of Cerenkov light and luminescence of water during carbon-ion irradiation. International journal

    Seiichi Yamamoto, Takuya Yabe, Takashi Akagi, Yoshiyuki Hirano

    Medical physics   Vol. 48 ( 1 ) page: 427 - 433   2021.1

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

    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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  16. Optical imaging of muons

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

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

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    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.

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  17. 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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  18. 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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    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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  19. 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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    DOI: 10.1088/2057-1976/ab8b7e

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

    Hirano, Y; Komori, M; Onoda, D; Nagae, T; Yamamoto, S

    JOURNAL OF PHYSICS COMMUNICATIONS   Vol. 4 ( 7 )   2020.7

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    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.

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  21. 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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    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-mu m-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 similar to 11 mu m. 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.

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  22. 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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  23. 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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  24. 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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    © 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.

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  25. 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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    © 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.

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  26. 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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    © 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.

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  27. 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%.

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  28. 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.

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  29. 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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  30. 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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  31. 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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  32. 陽子線、炭素線及びネオン線照射による水の発光効率のLET依存性

    小森 雅孝, 平野 祥之, 矢部 卓也, 堀田 遼, 米内 俊祐, 歳藤 利行, 山本 誠一

    日本放射線技術学会雑誌   Vol. 74 ( 9 ) page: 1004 - 1004   2018.9

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  33. 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.

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  34. 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 )   2018.3

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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.

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  35. 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   2018.2

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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.

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  36. 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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  37. 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.

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  38. 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

  39. 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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  40. 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

  41. 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

  42. 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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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)  

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

  43. 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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  44. 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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  45. 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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  46. 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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  47. 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

  48. 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

  49. 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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  50. 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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  51. 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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  52. 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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  53. 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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  54. 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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  55. 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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  56. 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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  57. 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

  58. 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

  59. 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

  60. 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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  61. 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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  62. 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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Presentations 20

  1. An estimation of produced oxygen in the track of heavy-ion using Geant4-DNA International conference

    Yoshiyuki Hirano, Tsukasa Aso, Yosyuya Horii

    Japan Society for Simulation Technology 2023  2023.8.29 

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    Event date: 2023.8

    Language:English   Presentation type:Oral presentation (general)  

  2. Range calculations with different stopping power tables in Monte Carlo simulationGeant4 in a carbon ion therapy

    Yoshiyuki Hirano, Akihiko Matsumura, Hikaru Souda

    2016.9 

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    Country:Japan  

  3. Effects of secondary particles on cell survivals estimated by a Monte Carlo simulation and microdosimetric kinetic model in carbon ion therapy

    Yoshiyuki Hirano

    2016.9 

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  4. Verification of the Oxygen in the heavy-ion track hypothesis in carbon-ion irradiation using Geant4-D

    2022.9 

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  5. Analysis of DNA damage by UVC and gamma rays using Raman spectroscopy

    2022.9 

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  6. Analysis of temporal variations of gene expression after gamma-ray irradiation in HeLa cells by RNA-seq

    2022.9 

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  7. Spectrum measurement of luminescence of water by synchrotron radiation beam with lower energy than the Cerenkov-light threshold

    Yoshiyuki Hirano, Masataka Komori, Yohei Kitao, Daichi Onoda, Seiichi Yamamoto

    2022.4 

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  8. Angular dependency of visible light imaging of water by radiations using a photon propagation simulation

    Yoshiyuki Hirano, Seiichi Yamamoto

    2019.4 

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  9. Estimation of amount of luminescence and Cerenkov lights in water irradiated by various types of radiations

    Yoshiyuki Hirano, Seiichi Yamamoto

    2019.4 

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  10. Effects of yield accuracy of secondary fragments on biological dose in heavy ion irradiations estimated by Monte Carlo simulation and microdosimetric kinetic model

    Yoshiyuki Hirano

    2019.9 

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  11. Range calculation in water irradiated by a carbon ion with updated ICRU stopping power table in Geant4

    Yoshiyuki Hirano

    2018.4 

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  12. An estimation of cell survival using microdosimetric kinetic model and CR-39 in carbon ion irradiation

    Hirano Yoshiyuki, Satoshi Kodaira, Ma Liqiu

    2017.4 

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  13. An application of microdosimetric kinetic model to targeted radionuclide therapy

    Yoshiyuki Hirano, Sumitaka Hasegawa

    2017.4 

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  14. Comparisons of Geant4 and experimental LET spectra in a C-12 irradiation and high Z fragments using CR-39 detector

    Yoshiyuki Hirano, Satoshi Kodaira, Hikaru Souda

    2017.9 

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  15. Effects of induced radioactivity of scintillators on in-beam OpenPET dedicated for dose verification in heavy ion therapy

    Yoshiyuki Hirano, Munetaka Nitta, Fumihiko Nishikido, Naoko Inadama, Eiji Yoshida, Taiga Yamaya

    2016.9 

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  16. Gene expression analysis of radio-resistance in human cell lines

    Yoshiyuki Hirano

    第125回日本医学物理学会  2023.4.13 

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  17. Estimation of cell survival irradiated by Cherenkov lights in radiation therapy

    Yoshiyuki Hirano

    第125回日本医学物理学会  2023.4.13 

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  18. Simulation study of the H abstraction from DNA sugar moiety by OH radicals using molecular dynamics and ab initio calculation

    2023.11.7 

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  19. Development of an affordable small-sized CO2 incubator for time-lapse monitoring of cells during and after irradiation

    2023.11.8 

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  20. Analysis of gene expression changes in human tumor cells after gamma irradiation using RNA-seq

    2023.11.7 

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KAKENHI (Grants-in-Aid for Scientific Research) 12

  1. Medical application of luminescence of water lower energy than Cherenkov-light threshold

    Grant number:22H03019  2022.4 - 2027.3

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

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  2. Mechanisms of cell survival response induced by oxygen environment after ionizing radiations

    Grant number:22H03032  2022.4 - 2026.3

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

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  3. 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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    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。
    昨年度にFLASH照射による水溶液内の放射線化学反応過程を追えるよう機能拡張したMPEXS-DNAで、研究分担者が行った陽子線FLASH照射の実験を模擬したシミュレーションを実施した。その実験とは、OHラジカルを捕獲して蛍光を呈するクマリン-3-カルボン酸(C3CA)が溶けた水溶液に陽子線を線量率を変えて照射し、7-ヒドロキシ-クマリン-3-カルボン酸(7OH-C3CA)の収率の線量率依存性を測定するものである。実験では線量率の増大により7OH-C3CAの収率が低下し10 Gy/s以降ほぼ一定となる結果を得たが、これをMPEXS-DNAシミュレーションでも再現した。但し、実験では収率低下率が60%程度であり、対してMPEXS-DNAは30%と両者に差がある。現状MPEXS-DNAに実装したC3CAに関連する反応速度定数等のパラメータが実現象に即しておらず今後の課題である。7OH-C3CAの収率低下の要因としては、FLASH照射により水溶液内の酸素濃度が極度に低下して7OH-C3CA生成に酸素が関わる経路が遮断されるためとされた。しかし、実験で各線量率での酸素消費量を見ると、7OH-C3CAの収率低下に見合うだけの酸素は消費されていなかった。この件もシミュレーションで再現できた。7OH-C3CAの収率低下の可能性のある別要因として、FLASH照射でOHラジカル同士の再結合が活性化し過酸化水素の生成が増えてOHラジカルが減少することが挙げられる。実際シミュレーションでは線量率の増大で過酸化水素の収率が増え、その量は7OH-C3CAの収率減少に十分見合う。この結果の検証のため、来年度には過酸化水素の収率の線量率依存性の実測値との比較を行う。
    更に電子線のFLASH照射時の水和電子の収率の経時変化の実測データとの比較も行い、MPEXS-DNAは概ね実測結果を再現することを確認した。
    電子線や陽子線によるFLASH照射実験をMPEXS-DNAで模擬したところ、シミュレーションで計算したOHラジカルや水和電子等の収率は実測結果を概ね再現できることを確認した。MPEXS-DNAをベースとしたFLASH照射シミュレーションモデルの開発は順調に進んでいると考える。これと並行して、MPEXS-DNAの化学過程の計算速度改善を行った。化学過程では近傍の分子種を探索して自身がどの分子種と拡散中に反応を起こすのかの判定を毎時間ステップ実施し、ここで最も時間を費やす。FLASH照射のシミュレーションでは扱う分子種の数が膨大になり計算時間が簡単に長大化する。そこで分子動力学法で利用される近接リスト法を参考にMPEXS-DNAの化学反応過程のコード改修を実施したところ、2倍弱の計算速度の向上を得られた。また、2022年秋にNVIDIAからAda Lovelaceアーキテクチャ採用のGeForce RTX 4090が発売されたので、昨年度購入したベンチマーク用の計算機のGPUを新世代のものへと換装した。GeForce RTX 4090はコア数が16,000以上、クロック周波数は2.5GHzに達し、GPUの換装だけで更に2倍の計算速度の向上が得られた。MPEXS-DNAは昨年度と比較して3-4倍も計算速度が上がり、FLASH照射シミュレーションの高速化に繋がった。
    現状MPEXS-DNAはC3CAが溶けた水溶液に陽子線をFLASH照射したときの、7OH-C3CAの収率の線量率依存性の測定結果を概ね再現できる段階にある。しかし、MPEXS-DNAで計算した7OH-C3CAの収率低下率は測定値と差があることを確認した。この要因を調べるため、実験体系とシミュレーションのモデル体系との間の差異や、MPEXS-DNAに実装したC3CAに関連する化学反応の反応速度定数などのパラメータを今一度精査する。
    7OH-C3CAの収率低下の機序を理解するための実験が研究分担者により実施される。過酸化水素の線量率依存性の実験データが提供され次第、シミュレーション結果との比較・検証を実施する。研究成果は学術論文の形でまとめていく。

  4. 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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    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。
    放射線によるDNA損傷では、高い酸素量の条件下で損傷が生じやすい酸素効果が知られている。本研究では、原子レベルのモンテカルロシミュレー ションを用いて、酸素がDNA損傷に与える機構とその影響を調べることを目的とする。昨年度までの成果を用いて令和4年度は、(1) 直接作用と間接作用の相互割合についての評価、(2)ハイドロキシルラジカルがDNA分子の水素引抜き反応を起こす活性化エネルギーを量子化学計算を用いて評価、そして(3)酸素分圧をシミュレーションに追加する機能開発と評価を実施した。下記にこれらの研究実績の概要を示す。
    (1)直接作用のエネルギー閾値に、水のイオン化ポテンシャル(10.79eV)を適用すると、間接作用の寄与は、全体の約3割であった。他研究の計算条件(KURBUC)を参考に、エネルギー閾値17.5eVを適用すると、全体の約9割が間接作用に起因する結果となった。閾値の厳密な絶対値は未だ確定しておらず、高い閾値が既存の測定結果を後押しすることを確認した。
    (2)量子力学計算を用いて、ヒドロキシルラジカルがヌクレオチドの水素引抜き反応を起こす際に必要な活性化エネルギーを1'から5''までの各水素で求めたところ、全て8kcal/mol以下であった。間接作用の損傷確率は、前年度成果で得られた水素へのラジカルのアクセス頻度と活性化エネルギーの大きさから考察できる。活性化エネルギーは充分に低く、アクセス頻度が損傷確率に大きな影響を与えることを示唆している。
    (3)シミュレーションへの酸素分圧を考慮する機能を組み込み、各酸素分圧におけるラジカル種の発生数を解析した。酸素分圧を変化させた場合でも、ヒドロキシルラジカルの濃度およびその時間変化に差異はないことが確認された。一方で、溶存酸素によってスーパーオキサイドアニオンが生成されることが分かった。次年度は、この点の詳細を研究する。
    DNA分子レベルでのシミュレーションが行える環境が整い、DNA分子の原子レベルで損傷を評価する手法についても概ね開発が完了している。更に、酸素分圧を導入することができるシミュレーションの機能開発も概ね完成しており、最終年度にて酸素分圧のさまざまな条件下において、その効果を評価するシミュレーションを行う段階に達している。今年度の研究成果を、次年度に国内外の学会で発表するための準備を進めている。以上の経緯から、研究は概ね順調に進展していると判断している。
    R4年度までに得られた成果をもとに、酸素分圧を変えた場合のシミュレーション計算を行い、DNA損傷に与える影響を評価する。研究分担者らによる分子動力学計算結果や測定における知見に基づいて、シミュレーション条件を設定する。特に、これまではハイドロキシルラジカルによる間接作用を主に評価してきたが、スーパーオキサイドアニオンに代表される高い溶存酸素下で発生するラジカル種に関しても、シミュレーションを行ってDNA損傷への酸素の影響を評価する。

  5. 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。
    当初は、放射線治療適用部位のがん細胞をできるだけ多く、ガンマ線照射前後の遺伝子発現データを取得することを目的としていたが、予算の都合とbiological replicateをなるべく増やしたいため、限られた細胞のみデータ取得することにした。過去の文献から放射線耐性のある細胞株2種類と、放射線感受性の高い細胞株2種類を選んだ。現在は、それぞれ1種類ずつ(HepG2とIMR32)において、2Gy照射後5時間のRNAを抽出し、RNA-seqによるデータを取得した。現在遺伝子発現差異の解析をしているところである。また残り2種類(KMRC2とHEC251)についても、同様に照射し、RNA-seqの依頼をした。平行して、コロニーアッセイによるこれらの生存率曲線を取得し、放射線耐性を調べる予定であったが、HepG2とIMR32はコロニーを形成しづらいことが分かり、当該研究室が行っていた手法では生存率曲線の取得が難しいことがわかった。コロニー形成をしない理由については不明だが、あまり薄い濃度で細胞を撒くと生存率が極めて悪いと考えられる。一般に濃度が濃いとコロニー同士が結合し、コロニーのカウントができないため薄く撒く必要がある。そこで、薄い濃度でもコロニーを形成できる下限の濃度を測定し、コロニーがあまり大きくなる前に、アッセイをすることにした。さらに顕微鏡で培養ディッシュ全体を撮影することで、染色等で剥がれる前のコロニー数のカウントを実施することにした。これにより、照射前後での遺伝子発現差異の他に、放射線耐性との関連についても調べることができるようになった。まもなくデータは取得できるので、本年度までに解析を終える予定である。
    やや遅れている理由としては、細胞培養に必要なインキュベータの調子が悪く(CO2濃度が不明になった)、新しく細胞株を購入することができなかった。新しいインキュベータを購入する予算がないため、CO2センサーを作成し、そのセンサーの値を参考に濃度設定をすることでなんとか回避した。またはじめて扱う細胞株は、コロニーを形成しづらく、当該研究室で行ってきた方法では、生存率を測定することができなかった。その改善方法について模索していたため、予定より遅れた。
    放射線感受性が高い細胞株と低い細胞株のガンマ線照射前後のRNAを抽出し、RNA-seqによるデータは取得できた。よって、放射線感受性とベースラインと照射後の遺伝子発現との関わりについて解析する予定である。はじめは基本的な解析として、遺伝子発現差異を検出して、それらのエンリッチメント解析をする。コロニーアッセイによる生存率曲線の測定については、順次実施していく。

  6. 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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    Authorship:Coinvestigator(s) 

  7. Effect of hypoxia on the repair process of radiation-induced DNA double-strand breaks

    Grant number:19K08215  2019.4 - 2022.3

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

    Hirayama Ryoichi

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    Authorship:Coinvestigator(s) 

    Cancer tissues contain hypoxic regions that are considered to be ineffective against anticancer drugs and ionizing radiation, and eradication of these hypoxic cancer cells is important in cancer therapy by ionizing radiations. Since hypoxic cells in cancer tissues remain hypoxic condition for a certain period of time after irradiation, it is not clear how radiation-induced double-strand breaks (DSBs) are modified by hypoxia. In this study, we examined DSBs and micronuclei formation on frequency to investigate the effects of oxic/hypoxia on the damage repair process at the DNA and chromosome levels. DSBs repair efficiency showed a decrease under hypoxic condition, and even heavy particle induced DSBs showed a similar trend. On the other hand, no effect of oxygen during repair was observed in micronuclei formation.

  8. Analysis of bio-molecule damaged by radiation and its application to model of radiation effects

    Grant number:18K07631  2018.4 - 2023.3

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

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    Authorship:Principal investigator 

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

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

    Grant number:18K12073  2018.4 - 2022.3

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

    Koshino Kazuhiro

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    Authorship:Coinvestigator(s) 

    The purpose of this study is to realize a new pharmacokinetic analysis that is robust and accurate against noise using machine learning based on neural network structures. Processes were divided into two parts: (1) denoising of projection data and (2) estimation of pharmacokinetic parameters for noisy data. The performance of the neural networks prepared for each process was evaluated. For denoising of the projection data, a peak signal-to-noise ratio of 38.0 ± 0.5 dB was achieved while reducing discontinuities in the body axis direction using a neural network with a three-dimensional convolutional layer and residual connections. For the estimation of pharmacokinetic parameters, an estimation error of -0.3±12.4% was achieved for blood flow estimation.

  10. Development of a stochastic DNA damage model with a molecular dynamics calculation

    Grant number:18K11650  2018.4 - 2022.3

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

    Aso Tsukasa

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    Authorship:Coinvestigator(s) 

    In this study, a Monte Carlo simulation framework based on Geant4-DNA was developed, for the purpose of evaluating DNA damages by using a stochastic model. The simulation imports DNA models from the proton data bank and is capable of simulating both the direct and the indirect DNA damages. We focused on tritium-induced DNA damages and verified that the ratio of single-strand breaks to double-strand breaks is consistent with the results of previous studies.

  11. 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.

  12. 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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