Updated on 2023/03/29

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 1

  1. Osaka University   Graduate School, Division of Natural Science

    - 2008.3

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    Country: Japan

Professional Memberships 2

  1. 日本医学物理学会

  2. 日本核医学学会

Awards 2

  1. IOP Publishing Outstanding Reviewer award

    2020.3  

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

  2. 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 59

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

    Yamamoto Seiichi, Yamashita Tomohiro, Kobashi Yusuke, Hirano Yoshiyuki, Akagi Takashi, Yokokawa Hiromu, Kataoka Jun

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

    Yamamoto Seiichi, Yabe Takuya, Hirano Yoshiyuki, Kataoka Jun

    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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  3. 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

  4. 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

    CiNii Research

  5. 3-D Optical Imaging System of Muon Beams Using a Silver Activated Zinc Sulfide (ZnS(Ag)) Sheet Combined With a Mirror

    Yamamoto Seiichi, Ninomiya Kazuhiko, Kawamura Naritoshi, Hirano Yoshiyuki

    IEEE TRANSACTIONS ON NUCLEAR SCIENCE   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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  6. Three-dimensional (3D) optical imaging of muon beam using a plastic scintillator plate in water

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

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   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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  7. 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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  8. 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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  9. 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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  10. 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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  11. 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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  12. 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:Japanese   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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  13. 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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  14. 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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  15. 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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  16. 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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  17. 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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    Language:Japanese   Publisher:Journal of Physics Communications  

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

    DOI: 10.1088/2399-6528/ab9f8d

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  18. 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)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    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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  19. 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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    DOI: 10.1088/1361-6560/ab8532

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  20. 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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    DOI: 10.1016/j.radmeas.2020.106299

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  21. 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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  22. 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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  23. 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.

    DOI: 10.1016/j.radmeas.2019.106207

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  24. 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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  25. 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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  26. 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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  27. 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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  28. 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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  29. 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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  30. 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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  31. 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.

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  32. 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.

    DOI: 10.1088/1361-6560/aaa453

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  33. 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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  34. 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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  35. 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

  36. 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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  37. 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

  38. 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

  39. 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

  40. 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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  41. 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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  42. 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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  43. 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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  44. 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

  45. 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

  46. 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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  47. 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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  48. 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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  49. 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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  50. 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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  51. 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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  52. 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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  53. 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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  54. 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

  55. 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

  56. 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

  57. 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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  58. 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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  59. 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 14

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

    2022.9 

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

    2022.9 

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    Language:Japanese   Presentation type:Poster presentation  

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

    2022.9 

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    Language:Japanese   Presentation type:Poster presentation  

  4. 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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  5. 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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  6. 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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  7. 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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  8. 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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  9. 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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  10. An application of microdosimetric kinetic model to targeted radionuclide therapy

    Yoshiyuki Hirano, Sumitaka Hasegawa

    2017.4 

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  11. 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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  12. 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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  13. 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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  14. 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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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。
    本研究では、高線量率超短時間照射 (FLASH) における酸素の化学反応過程を定量化する計算モデルを構築することが目的である。本研究の先行研究として、研究代表者はDNAスケールの微小領域において荷電粒子の放射線相互作用をシミュレートし、水の放射線分解で発生した活性種(OHラジカル等)の時間発展をモンテカルロ法で追跡するMPEXS-DNAを開発している。2021年度は、このMPEXS-DNAのフレームワークに入射粒子を所定の線量率でターゲットに対してFLASH照射する機能を実装した。
    <BR>
    FLASHに関連するコンピュータ・シミュレーションの結果がいくつか報告されている。その論文に記載の条件とほぼ同一条件でMPEXS-DNAでFLASHのシミュレーションを行い、活性種のG値の時間推移を調べた。短時間に大量の荷電粒子をパルス状でターゲットに照射するとターゲット内は荷電粒子の飛跡が密に存在し、それに沿って活性種等の化学反応が活性化される。そのため、ある一定時間の経過後、DNA損傷の主な要因とされるOHラジカル同士の再結合の頻度が増して、その数(G値)は顕著に減る。そして、その反応の生成物であるH2O2の数が増える。ここで一例として挙げたOHラジカル及びH2O2分子の時間推移の傾向は、参考論文に記載の結果と一致することを確認した。今後は、FLASH照射の実験結果を用いた比較を行い、シミュレーション結果の妥当性を検証していく。
    <BR>
    FLASHシミュレーションのベンチマークテストのため専用の計算機を一台購入した。従前よりMPEXS-DNAはGPUによる超並列計算で従来のシミュレータと比較して計算時間の劇的な短縮に成功している。FLASH照射より計算すべき活性種の数が急激に増加しても許容できる時間でシミュレーションが完了することも確認した。
    当初の予定では2021年度の後半から、並行してDNAの放射線損傷評価の簡易モデルの検証にも取り掛かる予定であったが、FLASH照射シミュレーションを実行するためのMPEXS-DNAの機能拡張と動作検証に時間を費やした。DNA損傷モデルの検証は、次年度に実施する。
    まずは照射粒子を電子と限定して、2021年度に機能拡張を行ったMPEXS-DNAでFLASHのシミュレーションを実行して活性種の時間推移を調べる。そして、電子によるFLASH照射の実験結果(研究分担者からの提供)と比較し、シミュレーション結果の妥当性を検証を行っていく。これと並行して、放射線によるDNA損傷モデルの検証も進めていく。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、酸素が多く含まれている条件下で損傷が進み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している。DNA損傷には、放射線による直接作用と、放射化学により水中で発生したラジカルが反応する間接作用がある。酸素効果は、間接作用に関係していると考えられ、ガンマ線や電子線で寄与が大きいとされている。そこで、令和3年度の研究では、トリチウム壊変により発生する低エネルギーベータ線に着目し、(1)間接作用でDNA鎖切断に至る分子反応の割合について調査するとともに、(2)酸素分圧条件を取り入れる計算手法を検討した。下記に、これらの研究実績の概要を示す。
    (1) 間接作用は、主にOHラジカルによるDNA分子の水素引抜き反応に起因すると考えられている。シミュレーションで発生したOHラジカルを平均反応時間拡散した位置を記録し、DNA構成原子の配置と照合してファンデルワールス半径内にある時に損傷が生じると仮定した。反応点に近い水素が引き抜かれたとして、損傷割合との関係を解析した。先行研究では反応割合は、各分子サイトの溶媒接触表面積(B.Blasubramanian et al. 1998)、あるいはOHラジカルのアクセス数(Yonetani et al. 2020)に関連しているとされ、本研究でもこれらの結果と同様の結果が得られた。これにより、本研究のモデル化は妥当であると確認できた。
    (2) 酸素分圧を考慮する計算には、通常のラジカル拡散を追跡する手法では計算コストが大きいことがわかった。そこで、Geant4-DNAのIRT(Independent Reaction Technique)の利用を検討した。高速化と酸素添加の手法への改善方法を検討し、開発方針を確定した。
    シミュレーションに間接作用を考慮するにあたり、当初はラジカル種を拡散しながらラジカル間反応を追跡する計算手法を用い、更に酸素分子を配置して酸素が関連する反応を追加する手法を導入することを予定していた。しかし、計算コストが大きく、計算時間の観点から実現が難しいことがわかった。その代わりに、IRT(Independent Reaction Technique)と呼ばれる手法を調査した。この手法では発生したラジカルのリストの中から、拡散係数と反応係数を基にした反応確率が最も高い反応過程を選び、その後に拡散を考慮した反応点を決定する。この手法を用いれば、酸素をラジカルのリストに加えることにより、酸素分圧の割合を模擬できることがわかった。当初の予定とは手法が異なるものの、更に高速な計算手法の実現へと検討が進んだ。酸素を考慮したシミュレーションを実施するにあたり、これは重要な進展である。今年度の研究成果は、次年度に日本生体医工学会で発表する予定となっている。以上の経緯から、研究は概ね順調に進展していると考えている。
    今年度得られた成果をもとに、酸素分圧を変化させ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。量子力学計算や分子動力学計算により、OHラジカルとDNA分子との反応についての解析も研究分担者を通じて継続的に研究を進め、得られた知見をモンテカルロシミュレーションに反映させる。モンテカルロシミュレーションでは、IRT手法を用いて、計算効率の高い計算手法を提案して実装を行っていく。これにより、酸素分圧とラジカルの生成分布、特にOHラジカルの時間的増減の推移を検証する。最終的に原子レベル・分子レベルでのDNAの分子損傷における酸素効果について評価を行う。

  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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    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。
    まず、当該研究室においては、RNA-seqのための細胞からRNAを抽出する作業ははじめてであるが、研究室における抽出プロトコルを確立し、安定して抽出できるようになった。RIN値については常に9以上であり、シーケンスは外注しているが、質のよいRNAを提供できるようになった。また、試しにHeLa細胞へのCo-60の照射前後のRNA-seqによる発現解析を行った。こちらも、当該研究室においては、バイオインフォマティクスによる解析ははじめてであるが、先行研究等を参考にし、解析手法を確立した。先行研究とほぼ同様な結果(発現遺伝子の一致等)が得られたので、本解析の妥当性が示された。本年度の前半の成果としては、主に実験プロトコルの確立がある。その後、放射線照射後、1、5、12時間後のRNA抽出実験を実施し、現在シーケンス中で、データが出来次第、主に遺伝子発現の時間発展について調べる予定である。
    本研究は、数種類の細胞について、照射前後の遺伝子発現差異と放射線感受性について調べることが目的の一つであるが、細胞を培養するためのインキュベータの不具合のため、放射線感受性を取得するための生存率曲線の測定が長期間出来なかった。インキュベータの不具合はCO2濃度計の故障が原因で、現在の濃度を知ることができなくなった。新しいインキュベータを購入する予算はないため、CO2濃度検出器モジュールを購入して、CO2濃度モニターシステムを自作し、この濃度を基準にして調節することで、細胞培養を再開することができた。このように原因究明と対策に時間がかかり、本年度の前半は細胞生存率曲線の測定等が出来なかった。
    実験プロトコルおよび解析手法が確立し、一時停止していた細胞培養も再開できたので、あとは数種類の細胞(放射線適用部位で購入可能なもの)を培養し、細胞生存率曲線を測定するのと平行して、照射前後のRNAを抽出し、RNA-seqによる遺伝子発現差異と放射線感受性について解析を進める。当初10種類を目標にしていたが、予算の都合とより精度の高いデータ取得のため、1条件で3サンプル測定することにしたため、5種類程度しか実施できないが、本年度中にすべてのデータを取得できそうである。

  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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  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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    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. 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 - 2023.3

    科学研究費助成事業  基盤研究(C)

    平野 祥之, 余語 克紀

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    Authorship:Principal investigator 

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

    放射線照射によるDNAのラマンスペクトルの変化を測定してきたが、サンプルの調整法等によって、スペクトルが安定しなかった。また照射と非照射の比較を行うための規格化についても、先行研究を参考にして硝酸ナトリウムを添加して、そのピークを規格化に用いる等の工夫を行ったがこちらも安定しなかった。またラマン顕微鏡は共同利用施設の装置を利用していたが、故障により使用できなくなり、別の共同利用装置を利用することになった。新しい装置は励起波長を532nmと785nmで選択でき、蛍光が目立たない785nmを使用することにした。最後にDNAを凍結乾燥させて測定したところ、これまでより詳細なスペクトルが得られた。これによりピークの変動が確認しやすくなり、紫外線やCo-60によるガンマ線の照射による変動も確認できた。一方でこれまでは乾燥DNAを測定していたが、水溶液での測定や金粒子によるSERS基盤を用いた表面増強ラマンスペクトル測定等も実施した。前者については3000~3500cm-1に見られる水のラマンスペクトルを規格化に用いることで照射と非照射の比較が可能であるが、乾燥DNAに比べるとピークが広がりスペクトルの構造を見るのにあまり適していなかった。後者については、表面増強効果があまり見られなかったが、焦点位置等、測定手法に改善の余地があると考えている。一方で量子化学計算についても取り組み、ピークの帰属を特定するのに利用する予定である。申請者は、これまで量子化学の経験はないが、既存の計算ツールを利用し、比較的簡単な分子でDNAの構成要素であるアデニン等の塩基における、Co-60を2kGy照射のラマンスペクトルの変化と、量子化学計算によるラマンスペクトルの変化を比較しピークの帰属を特定した。しかし実験と計算のスペクトルは完全には一致せず、今後の課題として残った。
    照射と非照射の比較を行うための規格化手法が確立できず、しばらく停滞していた。これまではvector normalizationを適用してきたが、微小な増減を確認するために有用であるかは十分検討する必要がある。またサンプル交換による対物レンズとの位置関係やサンプルの形状の変化等を補正することは難しいため、規格化は必要であるが、微小変化を検出できる安定した規格化は難しい。しかしピークのシフトについては、規格化手法に影響されないため、ピークシフトに注目して解析することにした。一方でDNAの量子化学計算を進めており、少数の塩基対をもつDNAについては安定構造の計算ができた。その構造におけるラマンスペクトルを計算し、ピークの帰属について特定することができる。
    規格化手法の確立に苦労したが、微小なピークの増減については解析が困難であると判断した。しかしサンプルを凍結乾燥させ、測定時間を長くすることで、十分な統計量をもったスペクトルを用いて照射および非照射のピークシフトについて解析する。これまでもスペクトルの変動は確認しているが、スペクトルの微分によるピークの検出、そのピーク位置に基づいた複数のVogit関数によるフィッティングによる、より詳細な解析を行うことでピークシフトや増減変化の検出を行う予定である。これにより紫外線やガンマ線等の線種によるDNAのラマンスペクトルの変化の違いを明らかにする。また量子化学計算と比較することで、損傷構造の予測を行う。

  9. 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.

  10. 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.

  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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