Nov. 2023, 56th Annual Meeting of Japan Health Physics Society, Excellent Presentation Award　　　　　　　　　　　　　　　
Dose-rate effects in human lens epithelial cells
Y. Matsuya,T Sato, N. Hamada

Oct. 2023, Hokkaido University, The best poster presentation award. The 9th Hokkaido University Cross-Departmental Symposium　　　　　　　　　　　　　　　
Development of a calculation code that predicts radiation effects on the human body at atomic scale
Y. Matsuya

2022, Japan Atomic Energy Agency, 2020 Chairman's Commendation (Research and Development Achievement Award/Implementation of epoch-making research and development)　　　　　　　　　　　　　　　
Development of track structure analysis code to elucidate irradiation effects from nano scale
T. Ogawa, T. Kai, Y. Matsuya

Mar. 2018, Hokkaido University Graduate School of Health Sciences, President’s special award in Graduate School of Health Sciences Hokkaido University　　　　　　　　　　　　　　　
Yusuke Matsuya

Oct. 2017, The 60th Japansese Radiation Research Society,, Excellent Presentation Award　　　　　　　　　　　　　　　
Investigation of cell survival under protracted exposure for various dose rates in consideration of cell cycle distribution
Y. Matsuya;S. J. McMahon;K. Tsutsumi;K. Sasaki;Y. Yoshii;R. Mori;J. Oikawa;H. Date;K. M. Prise

Sep. 2017, European Radiation Research Society (ERRS), Travel Award ERRS-GBS-2017　　　　　　　　　　　　　　　
Application of the IMK model to cell survival curves following the exposure to intensity modulated radiation fields
Y. Matsuya;S. J. McMahon;K. M. Prise;H. Date

Dec. 2016, The 22nd International Conference on Medical Physics (ICMP), ICMP2016 Anchali Krisanachinda Award (3rd)　　　　　　　　　　　　　　　
Optimization of the irradiation scheme in radiotherapy focusing on the dose and dose rate to the tumor and organs at risk
R. Yamada;Y. Matsuya;H. Date

Dec. 2016, The 22nd International Conference on Medical Physics (ICMP), ICMP2016 Anchali Krisanachinda Award (1st)　　　　　　　　　　　　　　　
Biophysical modeling for targeted and non-targeted effects on cells after irradiation
Y. Matsuya;K. Sasaki;Y. Yoshii;H. Date

Nov. 2016, The 72nd annual meeting of Japanese Society of Radiological Technology Hokkaido branch, Excellent Presentation Award (Radiation Therapy)　　　　　　　　　　　　　　　
Analysis of cell-cycle dynamics under long-term exposure at low dose rate
Oikawa J;Matsuya Y;Mori R;Date H

Oct. 2016, The 59th Japansese Radiation Research Society, Excellent Presentation Award　　　　　　　　　　　　　　　
Development of mathematical model for cell surviving fraction including non-targeted effect
Matsuya Y;Sasaki K;Yoshii Y;Date H

Oct. 2016, The 3rd Educational Symposium on Radiation and Health by Young Scientists, Poster Prize Winner (1st)　　　　　　　　　　　　　　　
A Cell-Killing Model of Targeted and Non-Targeted Effects Based on Microdosimetry and Biological Processes
Y. Matsuya;K. Sasaki;Y. Yoshii;G. Okuyama;T. Kimura;H. Date

Mar. 2015, Hokkaido University Graduate School of Health Sciences, President’s special award in Graduate School of Health Sciences Hokkaido University　　　　　　　　　　　　　　　
Yusuke Matsuya

Oct. 2014, The 2nd International Conference on Radiological Sciences and Technology, President’s special award　　　　　　　　　　　　　　　
Quantitative Estimation of DNA Lesions in the Cell nucleus in Consideration of the Dose Rate
Y. Matsuya;Y. Yoshii;K. Tsutsumi;K. Sasaki;H. Date

Mar. 2013, Clark Memorial Foundation, Hokkaido University, Clark award　　　　　　　　　　　　　　　
Yusuke Matsuya

Jan. 2013, Hokkaido University, Excellent Presentation Award　　　　　　　　　　　　　　　
Microdosimetric study on the lesions in cell nucleus after photon beam irradiations
Yusuke Matsuya

Sep. 2012, Hokkaido University, President’s special award in Department of Health Sciences Hokkaido University　　　　　　　　　　　　　　　
Yusuke Matsuya

Jun. 2010, Hokkaido University, Nitobe Award　　　　　　　　　　　　　　　
Yusuke Matsuya

Evaluation of the uncertainty in calculating nanodosimetric quantities due to the use of different interaction cross sections in Monte Carlo track structure codes
Carmen Villagrasa, Giorgio Baiocco, Zine-El-Abidine Chaoui, Michael Dingfelder, Sébastien Incerti, Pavel Kundrát, Ioanna Kyriakou, Yusuke Matsuya, Takeshi Kai, Alessio Parisi, Yann Perrot, Marcin Pietrzak, Jan Schuemann, Hans Rabus
PLOS One, 21, 1, e0340500, e0340500, Public Library of Science (PLoS), 09 Jan. 2026, [Peer-reviewed]
English, Scientific journal, Biological effects induced by diverse types of ionizing radiation are known to show important variations. Nanodosimetry is suitable for studying the link between these variations and the patterns of radiation interactions within nanometer-scale volumes, using experimental techniques complemented by Monte Carlo track structure (MCTS) simulations. However, predicted nanodosimetric quantities differ among MCTS codes, primarily because each code employs distinct molecular-scale particle interaction models. This multi-code study examines these variations for low-energy electrons (20–10,000 eV), which play a critical role in energy deposition and biological effects by virtually all types of ionizing radiation. Specifically, the hypothesis tested in this work is that inter-code variability in nanodosimetry results is mainly caused by differences in assumptions regarding total interaction cross sections. Ionization cluster size distributions and derived nanodosimetric parameters were simulated with seven MCTS codes (PARTRAC, PHITS-TS, MCwater, PTra, and three Geant4-DNA options) in liquid water as a surrogate for biological tissue. Significant inter-code differences were observed, especially at the lowest energies. They were substantially reduced upon replacing the original cross sections in each code with a common, averaged dataset, created ad-hoc for this study and not based on theoretical assumptions. For example, for 50 eV electrons in 8 nm spheres, the variability in the predicted mean ionization numbers decreased from 23% to 5%, and in the probability of inducing two or more ionizations from 34% to 7% (relative standard deviations). This quantification demonstrates that total interaction cross sections are the primary source of uncertainty at low electron energies. A sensitivity test using DNA damage simulations with the PARTRAC code revealed that cross section variations notably affect biological outcome predictions. Replacing the code’s original cross sections with the averaged ones increased the predicted double-strand break yield by up to 15%. These findings underscore the urgent need for improved characterization of low-energy electron interaction cross sections to reduce uncertainties in MCTS simulations and enhance mechanistic understanding of radiation-induced biological effects.

An initial G value of hydrated electrons updated by a dynamic Monte Carlo simulation
Takeshi Kai, Tomohiro Toigawa, Yusuke Matsuya, Yuho Hirata, Hidetsugu Tsuchida, Akinari Yokoya
RSC Advances, 2026
Scientific journal

Longitudinal Analysis of Male Fertility Using an Acr‐Luc Knock‐In Mouse Model: A Preclinical Platform for Reproductive Toxicity Testing
Hisanori Fukunaga, Ryosuke Seino, Yusuke Matsuya, Hiroyuki Takashima, Masayori Ishikawa, Yasuhito Onodera, Hiroki Shirato, Haruhiko Miyata, Kevin M. Prise
MedComm, Jan. 2026
Scientific journal

Development and validation of generalized Monte Carlo track-structure simulation model applicable to arbitrary ions in arbitrary materials
Tatsuhiko Ogawa, Yuho Hirata, Yusuke Matsuya, Takeshi Kai
Computer Physics Communications, 316, 109758, 109758, Elsevier BV, Nov. 2025, [Peer-reviewed]
Scientific journal

Equivalent relative biological effectiveness for cell survival and micronuclei formation: insights from a biophysical approach
Yusuke Matsuya, Ryo Saga, Yidi Wang, Tatsuhiko Sato
Medical Physics, 52, 10, e70040, Wiley, 30 Sep. 2025, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Abstract

Background

Micronuclei (MN), which are chromosome fragments, are formed after exposure to ionizing radiation. Radiation‐induced MN is currently used as a quantitative indicator of the chromosomal aberrations detectable at a relatively early phase (e.g., within one cell‐cycle progression). Meanwhile, the MN formation assay is also used to evaluate radiosensitivity (e.g., cell‐killing). As such, the technique to assay the MN formation has been followed with increasing interest. However, the meaning of MN and the corresponding cellular responses remains uncertain.

Purpose

This study presents a biophysical model for estimating MN frequency and theoretically explores the cellular responses associated with MN formation, such as the relationship between MN formation and cell survival.

Methods

We used an integrated microdosimetric‐kinetic (IMK) model that allows the prediction of cell survival after radiation exposure, and we extended the IMK model by introducing a probability of MN formation from lethal lesions by misrepair. To validate the developed model, we estimated the dose, linear energy transfer (LET), and dose‐rate dependencies of MN frequency as well as its relative biological effectiveness (RBE _MN ) and compared them to the corresponding experimental data reported in the literature and measured in this study. The estimation approach of MN frequency from cell survival data and vice versa was also tested.

Results

Our developed IMK model enables the prediction of the MN formation frequency and the RBE _MN depending on LET and dose rate for both cancer and normal cells. Comparing the experimental data within this work and the literature, the modeling study clearly shows that radiation‐induced MN is intrinsically related to cell killing after radiation exposure. Our model analyses confirmed that the RBE values for cell survival and MN frequency are equivalent under the same irradiation conditions.

Conclusions

The present model indicates that the analysis of MN is useful in both radiation therapy and radiation protection to quantitatively evaluate curative effects and histological damage at early stages after exposure.

Computational analysis of the spatial distributions of low-energy electrons generated via water photolysis and photoinjection into electrodes in water
Takeshi Kai, Tomohiro Toigawa, Yusuke Matsuya, Yuho Hirata, Hidetsugu Tsuchida, Akinari Yokoya
The Journal of Chemical Physics, 21 Apr. 2025, [Peer-reviewed]
Scientific journal

Multiple DNA damages induced by water radiolysis demonstrated using a dynamic Monte Carlo code
Takeshi Kai, Tomohiro Toigawa, Yusuke Matsuya, Yuho Hirata, Hidetsugu Tsuchida, Yuma Ito, Akinari Yokoya
COMMUNICATIONS CHEMISTRY, 8, 1, 06 Mar. 2025, [Peer-reviewed]
English, Scientific journal

Development of a chemical code applicable to ions based on the PHITS code for efficient and visual radiolysis simulations
Yusuke Matsuya, Yuji Yoshii, Tamon Kusumoto, Tatsuhiko Ogawa, Seiki Ohnishi, Yuho Hirata, Tatsuhiko Sato, Takeshi Kai
Physical Chemistry Chemical Physics, 27, 6887, 6898, Mar. 2025, [Peer-reviewed]
Scientific journal

Analytic and Monte Carlo calculations of dose-mean lineal energy for 1 MeV–1 GeV protons with application to radiation protection quality factor
Alexis Papadopoulos, Ioanna Kyriakou, Yusuke Matsuya, Miguel Antonio Cortés-Giraldo, Miguel Galocha-Oliva, Ianik Plante, Robert D. Stewart, Ngoc Hoang Tran, Weibo Li, Ioannis A. Daglis, Giovanni Santin, Petteri Nieminen, Sebastien Incerti, Dimitris Emfietzoglou
Radiation and Environmental Biophysics, Springer Science and Business Media LLC, 10 Feb. 2025, [Peer-reviewed]
English, Scientific journal, Abstract

Radiation quality for determining biological effects is commonly linked to the microdosimetric quantity lineal energy ( $$y$$ ) and to the dose-mean lineal energy ( $${y}_{\text{D } }$$ ). Calculations of $${y}_{\text{D } }$$ are typically performed by specialised Monte Carlo track-structure (MCTS) codes, which can be time-intensive. Thus, microdosimetry-based analytic models are potentially useful for practical calculations. Analytic model calculations of proton $${y}_{\text{D } }$$ and radiation protection quality factor ( $$Q$$ ) values in sub-micron liquid water spheres (diameter 10–1000 nm) over a broad energy range (1 MeV–1 GeV) are compared against MCTS simulations by PHITS, RITRACKS, and Geant4-DNA. Additionally, an improved analytic microdosimetry model is proposed. The original analytic model of Xapsos is refined and model parameters are updated based on Geant4-DNA physics model. Direct proton energy deposition is described by an alternative energy-loss straggling distribution and the contribution of secondary electrons is calculated using the dielectric formulation of the relativistic Born approximation. MCTS simulations of proton $${y}_{\text{D } }$$ values using the latest versions of the PHITS, RITRACKS, and Geant4-DNA are reported along with the Monte Carlo Damage Simulation (MCDS) algorithm. The $${y}_{\text{D } }$$ datasets are then used within the Theory of Dual Radiation Action (TDRA) to illustrate variations in $$Q$$ with proton energy. By a careful selection of parameters, overall differences at the ~ 10% level between the proposed analytic model and the MCTS codes can be attained, significantly improving upon existing models. MCDS estimates of $${y}_{\text{D } }$$ are generally much lower than estimates from MCTS simulations. The differences of $$Q$$ among the examined methods are somewhat smaller than those of $${y}_{\text{D } }$$ . Still, estimates of proton $$Q$$ values by the present model are in better agreement with MCTS-based estimates than the existing analytic models. An improved microdosimetry-based analytic model is presented for calculating proton $${y}_{\text{D } }$$ values over a broad range of proton energies (1 MeV–1 GeV) and target sizes (10–1000 nm) in very good agreement with state-of-the-art MCTS simulations. It is envisioned that the proposed model might be used as an alternative to CPU-intensive MCTS simulations and advance practical microdosimetry and quality factor calculations in medical, accelerator, and space radiation applications.

Inverse dose protraction effects of low-LET radiation: evidence and significance
Nobuyuki Hamada, Yusuke Matsuya, Lydia B. Zablotska, Mark P. Little
Mutation Research - Reviews in Mutation Research, 108531, 108531, Elsevier BV, Jan. 2025, [Peer-reviewed]
Scientific journal

Inverse dose protraction effects of high-LET radiation: evidence and significance
Nobuyuki Hamada, Yusuke Matsuya, Lydia B. Zablotska, Mark P. Little
Mutation Research - Reviews in Mutation Research, 108530, 108530, Elsevier BV, Jan. 2025, [Peer-reviewed]
English, Scientific journal

Reply to Comments on ‘Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation’
Yuta Shiraishi, Yusuke Matsuya, Hisanori Fukunaga
Physics in Medicine & Biology, 69, 24, 248002, 248002, IOP Publishing, 12 Dec. 2024, [Peer-reviewed], [Corresponding author]
English, Scientific journal, Abstract

Liew and Mairani (2024 Phys. Med. Biol. 69 248001) commented on our previous reply to comments on our paper, ‘Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation’. We appreciate their comments on the choice of experimental data on DNA damage for cell survival and agree that the estimate of the dose-response curve on cell survival depends on the selection of DNA damage data. As an additional benchmark test, we compared the relative biological effectiveness (RBE) predicted using the recommended DNA damage data measured in normoxia with those reported in our original paper, and confirmed that the difference in RBE was less than 8%. Although our model allows for the estimation of cell survival and RBE under ultra-high dose rate (UHDR) irradiation, we highlight that a further accumulation of experimental data on DNA damage under UHDR irradiation is necessary for the further development of biophysical models concerning the mechanistical estimation of biological effects.

Application of radiation transport analysis code PHITS to life sciences
Yusuke Matsuya, Takeshi Kai, Tatsuhiko Sato
原子衝突学会誌しょうとつ, 21, 3, R008-1, R008-8, 15 Nov. 2024, [Peer-reviewed], [Invited], [Lead author, Corresponding author]
Japanese

Development of PHITS track structure calculations and their applications to clarify the response mechanism of radiation detectors　　　　　　　　　　　　　　　
Y. Hirata, T. Kai, T. Ogawa, Y. Matsuya, T. Sato
放射化学, 118, 21, 28, Nov. 2024, [Peer-reviewed], [Invited]

Overview of PHITS Ver.3.34 with particular focus on track-structure calculation
Tatsuhiko Ogawa, Yuho Hirata, Yusuke Matsuya, Takeshi Kai, Tatsuhiko Sato, Yosuke Iwamoto, Shintaro Hashimoto, Takuya Furuta, Shin-ichiro Abe, Norihiro Matsuda, Takuya Sekikawa, Lan Yao, Pi-En Tsai, Hunter N. Ratliff, Hiroshi Iwase, Yasuhito Sakaki, Kenta Sugihara, Nobuhiro Shigyo, Lembit Sihver, Koji Niita
EPJ Nuclear Sciences & Technologies, 10, 13, 13, EDP Sciences, 01 Nov. 2024, [Peer-reviewed]
Scientific journal, This paper presents the latest updates on PHITS, a versatile radiation transport code, focusing specifically on track-structure models. Track structure calculations are methods used to simulate the movement of charged particles while explicitly considering each atomic reaction. Initially developed for radiation biology, these calculation methods aimed to analyze the radiation-induced damage to DNA and chromosomes. Several track-structure calculation models, including PHITS-ETS, PHITS-ETS for Si, PHITS-KURBUC, ETSART, and ITSART, have been developed and implemented for PHITS. These models allow users to study the behavior of various particles at the nano-scale across a wide range of materials. Furthermore, potential applications of track-structure calculations have also been proposed so far. This collection of track-structure calculation models, which encompasses diverse conditions, opens up new avenues for research in the field of radiation effects.

Significant role of secondary electrons in the formation of a multi-body chemical species spur produced by water radiolysis
Takeshi Kai, Tomohiro Toigawa, Yusuke Matsuya, Yuho Hirata, Tomoya Tezuka, Hidetsugu Tsuchida, Akinari Yokoya
Scientific Reports, 14, 1, Springer Science and Business Media LLC, 21 Oct. 2024, [Peer-reviewed]
Scientific journal, Abstract

Scientific insights into water photolysis and radiolysis are essential for estimating the direct and indirect effects of deoxyribonucleic acid (DNA) damage. Secondary electrons from radiolysis intricately associated with both effects. In our previous paper, we simulated the femtosecond (1 × 10^− 15 s) dynamics of secondary electrons ejected by energy depositions of 11−19 eV into water via high-energy electron transport using a time-dependent simulation code. The results contribute to the understanding of simple “intra-spur” chemical reactions of tree-body chemical species (hydrated electrons, hydronium ion and OH radical) in subsequent chemical processes. Herein, we simulate the dynamics of the electrons ejected by energy depositions of 20−30 eV. The present results contribute to the understanding of complex “inter-spur” chemical reactions of the multi-body chemical species as well as for the formation of complex DNA damage with redox site and strand break on DNA. The simulation results present the earliest formation mechanism of an unclear multi-body chemical species spur when secondary electrons induce further ionisations or electronic excitations. The formation involves electron–water collisions, i.e. ionisation, electronic excitation, molecular excitation and elastic scattering. Our simulation results indicate that (1) most secondary electrons delocalise to ~ 12 nm, and multiple collisions are sometimes induced in a water molecule at 22 eV deposition energy. (2) The secondary electrons begin to induce diffuse band excitation of water around a few nm from the initial energy deposition site and delocalise to ~ 8 nm at deposition energies ~ 25 eV. (3) The secondary electron can cause one additional ionisation or electronic excitation at deposition energies > 30 eV, forming a multi-body chemical species spur. Thus, we propose that the type and density of chemical species produced by water radiolysis strongly depend on the deposition energy. From our results, we discuss formation of complex DNA damage.

Radiation research trends by young scientists and the future tasks in Northern Japan: report on ‘the 10th educational symposium on radiation and health (ESRAH) by young scientists in 2023’
Ryosuke Seino, Hiroki Hashimoto, Haruka Kuwata, Worawat Poltabtim, Khemruthai Kheamsiri, Radhia Pradana, Saowarak Musikawan, Yuki Abe, Manaya Taoka, Rui Kudo, Chutima Kranrod, Hironori Yoshino, Masahiro Hosoda, Yusuke Matsuya
International Journal of Radiation Biology, 1, 6, Informa UK Limited, Oct. 2024
Scientific journal

Liquid water radiolysis induced by secondary electrons generated from MeV-energy carbon ions
Hidetsugu Tsuchida, Tomoya Tezuka, Takeshi Kai, Yusuke Matsuya, Takuya Majima, Manabu Saito
The Journal of Chemical Physics, 161, 10, AIP Publishing, 10 Sep. 2024, [Peer-reviewed]
Scientific journal, Fast ion beams induce damage to deoxyribonucleic acid (DNA) by chemical products, including secondary electrons, produced from interaction with liquid water in living cells. However, the production process of these chemical products in the Bragg peak region used in particle therapy is not fully understood. To investigate this process, we conducted experiments to evaluate the radiolytic yields produced when a liquid water jet in vacuum is irradiated with MeV-energy carbon beams. We used secondary ion mass spectrometry to measure the products, such as hydronium cations (H3O+) and hydroxyl anions (OH−), produced along with ·OH radicals, which are significant inducers of DNA damage formation. In addition, we simulated the ionization process in liquid water by incident ions and secondary electrons using a Monte Carlo code for radiation transport. Our results showed that secondary electrons, rather than incident ions, are the primary cause of ionization in water. We found that the production yield of H3O+ or OH− was linked to the frequency of ionization by secondary electrons in water, with these electrons having energies between 10.9 and 550 eV. These electrons are responsible for ionizing the outer-shell electrons of water molecules. Finally, we present that the elementary processes contribute to advancing radiation biophysics and biochemistry, which study the formation mechanism of DNA damage.

In vitro and in silico study of biological effects on cancer cells in the presence of metallic materials during radiotherapy
Takuya Nagano, Yusuke Matsuya, Atsushi Kaida, Hitomi Nojima, Takuya Furuta, Kaoru Sato, Ryoichi Yoshimura, Masahiko Miura
Journal of Radiation Research, Oxford University Press (OUP), 22 Aug. 2024, [Peer-reviewed]
English, Scientific journal, Abstract

X-ray therapy aims to eliminate tumours while minimizing side effects. Intense mucositis is sometimes induced when irradiating the oral cavity with a dental metal crown (DMC). However, the underlying mechanisms of such inducing radiosensitization by DMC remain uncertain. This study explored the radiosensitizing mechanisms around DMCs in an interdisciplinary approach with cell experiments and Monte Carlo simulation with the PHITS code. Clonogenic survival and nuclear 53BP1 foci of a cell line derived from cervical cancer cells (HeLa cells) were measured post-irradiation with therapeutic X-rays near high-Z materials such as Pb or Au plates, and the experimental sensitizer enhancement ratio (SER) was obtained. Meanwhile, the dose enhancement ratio (DER) and relative biological effectiveness for DNA damage yields were calculated using the PHITS code, by considering the corresponding experimental condition. The experiments show the experimental SER values for cell survival and 53BP1 foci near metals are 1.2–1.4, which agrees well with the calculated DER values. These suggest that the radiosensitizing effects near metal are predominantly attributed to the dose increase. In addition, as a preclinical evaluation, the spatial distributions of DER near DMC are calculated using Computed Tomography Digital Imaging and Communications in Medicine (CT-DICOM) data and a simple tooth model. As a result, the DER values evaluated using the CT-DICOM data were lower than those from a simple tooth model. These findings highlight the challenge of evaluating radiosensitizing effects near DMCs using Digital Imaging and Communications in Medicine (DICOM) images due to volume-averaging effects and emphasize the need for a high-resolution (<1 mm) dose assessment method unaffected by these effects.

Cell-cycle dependence on the biological effects of boron neutron capture therapy and its modification by polyvinyl alcohol
Yusuke Matsuya, Tatsuhiko Sato, Tamon Kusumoto, Yoshie Yachi, Ryosuke Seino, Misako Miwa, Masayori Ishikawa, Shigeo Matsuyama, Hisanori Fukunaga
Scientific Reports, 14, 1, Springer Science and Business Media LLC, 19 Jul. 2024, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Abstract

Boron neutron capture therapy (BNCT) is a unique radiotherapy of selectively eradicating tumor cells using boron compounds (e.g., 4-borono-l-phenylalanine [BPA]) that are heterogeneously taken up at the cellular level. Such heterogenicity potentially reduces the curative efficiency. However, the effects of temporospatial heterogenicity on cell killing remain unclear. With the technical combination of radiation track detector and biophysical simulations, this study revealed the cell cycle-dependent heterogenicity of BPA uptake and subsequent biological effects of BNCT on HeLa cells expressing fluorescent ubiquitination-based cell cycle indicators, as well as the modification effects of polyvinyl alcohol (PVA). The results showed that the BPA concentration in the S/G₂/M phase was higher than that in the G₁/S phase and that PVA enhances the biological effects both by improving the uptake and by canceling the heterogenicity. These findings might contribute to a maximization of therapeutic efficacy when BNCT is combined with PVA and/or cell cycle-specific anticancer agents.

Evaluation of relative biological effectiveness for diseases of the circulatory system based on microdosimetry
Tatsuhiko Sato, Yusuke Matsuya, Nobuyuki Hamada
Journal of Radiation Research, 65, 4, 500, 506, Oxford University Press (OUP), 26 Jun. 2024, [Peer-reviewed]
Scientific journal, Abstract

In the next decade, the International Commission on Radiological Protection (ICRP) will issue the next set of general recommendations, for which evaluation of relative biological effectiveness (RBE) for various types of tissue reactions would be needed. ICRP has recently classified diseases of the circulatory system (DCS) as a tissue reaction, but has not recommended RBE for DCS. We therefore evaluated the mean and uncertainty of RBE for DCS by applying a microdosimetric kinetic model specialized for RBE estimation of tissue reactions. For this purpose, we analyzed several RBE data for DCS determined by past animal experiments and evaluated the radius of the subnuclear domain best fit to each experiment as a single free parameter included in the model. Our analysis suggested that RBE for DCS tends to be lower than that for skin reactions, and their difference was borderline significant due to large variances of the evaluated parameters. We also found that RBE for DCS following mono-energetic neutron irradiation of the human body is much lower than that for skin reactions, particularly at the thermal energy and around 1 MeV. This tendency is considered attributable not only to the intrinsic difference of neutron RBE between skin reactions and DCS but also to the difference in the contributions of secondary γ-rays to the total absorbed doses between their target organs. These findings will help determine RBE by ICRP for preventing tissue reactions.

The impact of dose rate on responses of human lens epithelial cells to ionizing irradiation
Yusuke Matsuya, Tatsuhiko Sato, Yoshie Yachi, Hiroyuki Date, Nobuyuki Hamada
Scientific Reports, 14, 1, Springer Science and Business Media LLC, 28 May 2024, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Abstract

The knowledge on responses of human lens epithelial cells (HLECs) to ionizing radiation exposure is important to understand mechanisms of radiation cataracts that are of concern in the field of radiation protection and radiation therapy. However, biological effects in HLECs following protracted exposure have not yet fully been explored. Here, we investigated the temporal kinetics of γ-H2AX foci as a marker for DNA double-strand breaks (DSBs) and cell survival in HLECs after exposure to photon beams at various dose rates (i.e., 150 kVp X-rays at 1.82, 0.1, and 0.033 Gy/min, and ¹³⁷Cs γ-rays at 0.00461 Gy/min (27.7 cGy/h) and 0.00081 Gy/min (4.9 cGy/h)), compared to those in human lung fibroblasts (WI-38). In parallel, we quantified the recovery for DSBs and cell survival using a biophysical model. The study revealed that HLECs have a lower DSB repair rate than WI-38 cells. There is no significant impact of dose rate on cell survival in both cell lines in the dose-rate range of 0.033–1.82 Gy/min. In contrast, the experimental residual γ-H2AX foci showed inverse dose rate effects (IDREs) compared to the model prediction, highlighting the importance of the IDREs in evaluating radiation effects on the ocular lens.

DNA damage response in a 2D-culture model by diffusing alpha-emitters radiation therapy (Alpha-DaRT)
Hitomi Nojima, Atsushi Kaida, Yusuke Matsuya, Motohiro Uo, Ryo-ichi Yoshimura, Lior Arazi, Masahiko Miura
Scientific Reports, 14, 1, Springer Science and Business Media LLC, 20 May 2024, [Peer-reviewed]
English, Scientific journal, Abstract

Diffusing alpha-emitters radiation therapy (Alpha-DaRT) is a unique method, in which interstitial sources carrying ²²⁴Ra release a chain of short-lived daughter atoms from their surface. Although DNA damage response (DDR) is crucial to inducing cell death after irradiation, how the DDR occurs during Alpha-DaRT treatment has not yet been explored. In this study, we temporo-spatially characterized DDR such as kinetics of DNA double-strand breaks (DSBs) and cell cycle, in two-dimensional (2D) culture conditions qualitatively mimicking Alpha-DaRT treatments, by employing HeLa cells expressing the Fucci cell cycle-visualizing system. The distribution of the alpha-particle pits detected by a plastic nuclear track detector, CR-39, strongly correlated with γH2AX staining, a marker of DSBs, around the ²²⁴Ra source, but the area of G2 arrested cells was more widely spread 24 h from the start of the exposure. Thereafter, close time-lapse observation revealed varying cell cycle kinetics, depending on the distance from the source. A medium containing daughter nuclides prepared from ²²⁴Ra sources allowed us to estimate the radiation dose after 24 h of exposure, and determine surviving fractions. The present experimental model revealed for the first time temporo-spatial information of DDR occurring around the source in its early stages.

Reply to comment on ‘Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation’
Yuta Shiraishi, Yusuke Matsuya, Hisanori Fukunaga
Physics in Medicine & Biology, 69, 10, 108002, 108002, IOP Publishing, 03 May 2024, [Peer-reviewed], [Corresponding author]
Scientific journal, Abstract

Liew and Mairani commented on our paper ‘Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation’ (Shiraishi et al 2024a Phys. Med. Biol.69 015017), which proposed a biophysical model to predict the dose–response curve of surviving cell fractions after ultra-high dose rate irradiation following conventional dose rate irradiation by considering DNA damage yields. They suggested the need to consider oxygen concentration in our prediction model and possible issues related to the data selection process used for the benchmarking test in our paper. In this reply, we discuss the limitations of both the present model and the available experimental data for determining the model’s parameters. We also demonstrate that our proposed model can reproduce the experimental survival data even when using only the experimental DNA damage data measured reliably under normoxic conditions.

Changes in molecular conformation and electronic structure of DNA under 12C ions based on first-principles calculations
Takuya Sekikawa, Yusuke Matsuya, Beomju Hwang, Masato Ishizaka, Hiroyuki Kawai, Yoshiaki Ōno, Tatsuhiko Sato, Takeshi Kai
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 548, 165231, 165231, Elsevier BV, Mar. 2024, [Peer-reviewed]
Scientific journal

Meeting Report on “The 9th Educational Symposium on Radiation and Health by Young Scientists (ESRAH 2022)”
Hiroki Hashimoto, Ryo Nakayama, Haruka Kuwata, Worawat Poltabtim, Ryosuke Seino, Reima Fukuda, Khemruthai Kheamsiri, Radhia Pradana, Yuki Oda, Mizuki Kiso, Aoi Sampei, Chutima Kranrod, Hironori Yoshino, Yusuke Matsuya, Masahiro Hosoda
Radiation Environment and Medicine, 13, 1, 35, 43, 28 Feb. 2024, [Peer-reviewed]
English, Scientific journal

Development of a model for evaluating the luminescence intensity of phosphors based on the PHITS track-structure simulation
Yuho Hirata, Takeshi Kai, Tatsuhiko Ogawa, Yusuke Matsuya, Tatsuhiko Sato
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 547, 165183, 165183, Elsevier BV, Feb. 2024, [Peer-reviewed]
Scientific journal

Possible mechanisms and simulation modeling of FLASH radiotherapy
Yuta Shiraishi, Yusuke Matsuya, Hisanori Fukunaga
Radiological Physics and Technology, Springer Science and Business Media LLC, 06 Jan. 2024, [Peer-reviewed]
Scientific journal

Generality assessment of a model considering heterogeneous cancer cells for predicting tumor control probability for stereotactic body radiotherapy against non-small cell lung cancer
Ryo Saga, Yusuke Matsuya, Hideki Obara, Fumio Komai, Hironori Yoshino, Masahiko Aoki, Yoichiro Hosokawa
Advances in Radiation Oncology, 101437, 101437, Elsevier BV, Jan. 2024, [Peer-reviewed]
Scientific journal

A step-by-step simulation code for estimating yields of water radiolysis species based on electron track-structure mode in the PHITS code
Yusuke Matsuya, Yuji Yoshii, Tamon Kusumoto, Ken Akamatsu, Yuho Hirata, Tatsuhiko Sato, Takeshi Kai
Physics in Medicine & Biology, IOP Publishing, 29 Dec. 2023, [Peer-reviewed], [Lead author, Corresponding author]
Scientific journal, Abstract

Objective. Time-dependent yields of chemical products resulting from water radiolysis play a great role in evaluating DNA damage response after exposure to ionizing radiation. Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo simulation code for radiation transport, which simulates atomic interactions originating from discrete energy levels of ionizations and electronic excitations as well as molecular excitations as physical stages. However, no chemical code for simulating water radiolysis products exists in the PHITS package. Approach. Here, we developed a chemical simulation code dedicated to the PHITS code, hereafter called PHITS-Chem code, which enables the calculation of the G values of water radiolysis species (^•OH, e_aq^-, H₂, H₂O₂ etc.) by electron beams. Main results. The estimated G values during 1 μs are in agreement with the experimental ones and other simulations. This PHITS-Chem code also simulates the radiolysis in the presence of OH radical scavengers, such as tris(hydroxymethyl)aminomethane and dimethyl sulfoxide. Thank to this feature, the contributions of direct and indirect effects on DNA damage induction under various scavenging capacities can be analyzed. Significance. This chemical code coupled with PHITS could contribute to elucidating the mechanism of radiation effects by connecting physical, physicochemical, and chemical processes.

Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation
Yuta Shiraishi, Yusuke Matsuya, Tamon Kusumoto, Hisanori Fukunaga
Physics in Medicine & Biology, 69, 1, 015017, 015017, IOP Publishing, 26 Dec. 2023, [Peer-reviewed]
Scientific journal, Abstract

Objective. FLASH radiotherapy (FLASH-RT) with ultra-high dose rate (UHDR) irradiation (i.e. > 40 Gy s⁻¹) spares the function of normal tissues while preserving antitumor efficacy, known as the FLASH effect. The biological effects after conventional dose rate-radiotherapy (CONV-RT) with ≤0.1 Gy s⁻¹ have been well modeled by considering microdosimetry and DNA repair processes, meanwhile modeling of radiosensitivities under UHDR irradiation is insufficient. Here, we developed an integrated microdosimetric-kinetic (IMK) model for UHDR-irradiation enabling the prediction of surviving fraction after UHDR irradiation. Approach. The IMK model for UHDR-irradiation considers the initial DNA damage yields by the modification of indirect effects under UHDR compared to CONV dose rate. The developed model is based on the linear-quadratic (LQ) nature with the dose and dose square coefficients, considering the reduction of DNA damage yields as a function of dose rate. Main results. The estimate by the developed model could successfully reproduce the in vitro experimental dose–response curve for various cell line types and dose rates. Significance. The developed model would be useful for predicting the biological effects under the UHDR irradiation.

Recent improvements of the particle and heavy ion transport code system – PHITS version 3.33
Tatsuhiko Sato, Yosuke Iwamoto, Shintaro Hashimoto, Tatsuhiko Ogawa, Takuya Furuta, Shin-Ichiro Abe, Takeshi Kai, Yusuke Matsuya, Norihiro Matsuda, Yuho Hirata, Takuya Sekikawa, Lan Yao, Pi-En Tsai, Hunter N. Ratliff, Hiroshi Iwase, Yasuhito Sakaki, Kenta Sugihara, Nobuhiro Shigyo, Lembit Sihver, Koji Niita
Journal of Nuclear Science and Technology, 1, 9, Informa UK Limited, 31 Oct. 2023, [Peer-reviewed]
English, Scientific journal

First-principles simulation of an ejected electron produced by monochromatic deposition energy to water at the femtosecond order.
Takeshi Kai, Tomohiro Toigawa, Yusuke Matsuya, Yuho Hirata, Tomoya Tezuka, Hidetsugu Tsuchida, Akinari Yokoya
RSC advances, 13, 46, 32371, 32380, 31 Oct. 2023, [Peer-reviewed], [International Magazine]
English, Scientific journal, This study uses a time-dependent first-principles simulation code to investigate the transient dynamics of an ejected electron produced in the monochromatic deposition energy from 11 to 19 eV in water. The energy deposition forms a three-body single spur comprising a hydroxyl radical (OH˙), hydronium ion (H3O+), and hydrated electron (eaq-). The earliest formation involves electron thermalization and delocalization dominated by the molecular excitation of water. Our simulation results show that the transient electron dynamics primarily depends on the amount of deposition energy to water; the thermalization time varies from 200 to 500 fs, and the delocalization varies from 3 to 10 nm in this energy range. These features are crucial for determining the earliest single-spur formation and facilitating a sequential simulation from an energy deposition to a chemical reaction in water photolysis or radiolysis. The spur radius obtained from the simulation correlates reasonably with the experimental-based estimations. Our results should provide universalistic insights for analysing ultrafast phenomena dominated by the molecular excitation of water in the femtosecond order.

Development of an electron track-structure mode for arbitrary semiconductor materials in PHITS
Yuho Hirata, Takeshi Kai, Tatsuhiko Ogawa, Yusuke Matsuya, Tatsuhiko Sato
Japanese Journal of Applied Physics, 62, 10, 106001, 106001, IOP Publishing, 01 Oct. 2023, [Peer-reviewed]
English, Scientific journal, Abstract

Optimizing the design of semiconductor detector requires an electron track-structure code that can trace an incident electron motion with energies down to a few eV and simulate the production process of excited electrons in semiconductors. We therefore developed an Electron Track Structure mode applicable to ARbitrary Targets (ETSART) and implemented it into Particle and Heavy Ion Transport code System (PHITS). ETSART can simulate the electrons’ motion in arbitrary semiconductor materials using their bandgap energies. The accuracy of ETSART was validated by comparing the calculated electron path lengths in semiconductor materials with the corresponding data in the ICRU Report 37. Using ETSART, we also computed the mean energy required to produce an electron–hole pair (epsilon value) in various semiconductors and found that the epsilon value varies nonlinearly with the bandgap energy. Thus, ETSART can be useful for initial and mechanistic evaluations of electron–hole pair formation in new materials.

Biophysical Simulations for Estimating Biological Effects after Exposure to Ionizing Radiation: Current State and Future Prospects
Yusuke Matsuya, Ryo Saga
Radiation Environment and Medicine, 12, 2, 81, 90, 29 Aug. 2023, [Peer-reviewed], [Invited], [Lead author, Corresponding author]
English, Scientific journal

Improvement of the hybrid approach between Monte Carlo simulation and analytical function for calculating microdosimetric probability densities in macroscopic matter
Tatsuhiko Sato, Yusuke Matsuya, Tatsuhiko Ogawa, Takeshi Kai, Yuho Hirata, Shuichi Tsuda, Alessio Parisi
Physics in Medicine & Biology, 68, 155005, 07 Aug. 2023, [Peer-reviewed]
English, Scientific journal, In this study, we improved the microdosimetric function implemented in PHITS using the latest track-structure simulation codes. The improved function is capable of calculating the probability densities of not only the conventional microdosimetric quantities such as lineal energy but also the numbers of ionization events occurred in a target site, the so-called ionization cluster size distribution, for arbitrary site diameters from 3 nm to 1 um. As a new application of the improved function, we calculated the relative biological effectiveness of the single-strand break and double-strand break yields for proton irradiations using the updated PHITS coupled with the simplified DNA damage estimation model, and confirmed its equivalence in accuracy and its superiority in computational time compared to our previously proposed method based on the track-structure simulation.

Translational study for stereotactic body radiotherapy against non-small cell lung cancer, including oligometastases, considering cancer stem-like cells enable predicting clinical outcome from in vitro data
Ryo Saga, Yusuke Matsuya, Hikari Sato, Kazuki Hasegawa, Hideki Obara, Fumio Komai, Hironori Yoshino, Masahiko Aoki, Yoichiro Hosokawa
Radiotherapy and Oncology, 181, 109444, 109444, Elsevier BV, Apr. 2023, [Peer-reviewed], [Lead author]
Scientific journal

Modelling oxygen effects on the in- and out-of-field radiosensitivity of cells exposed to intensity-modulated radiation fields
Yusuke Matsuya, Stephen J McMahon, Karl T Butterworth, Yoshie Yachi, Ryo Saga, Tatsuhiko Sato, Kevin M Prise
Physics in Medicine & Biology, IOP Publishing, 23 Mar. 2023, [Lead author, Corresponding author]
Scientific journal, Abstract

Objective: The delivery of intensity-modulated radiation fields has improved the conformity of dose to tumour targets during radiotherapy (RT). Previously, it has been shown that intercellular communication between cells positioned in- and outside of the radiation field impacts cellular radiosensitivity under hypoxic and normoxic conditions. However, the mechanism of intercellular communication in hypoxia remains to be fully understood. In this study, the cell-killing effects of intercellular communication in hypoxia were modelled in an effort to better understand the underlying mechanisms of response. 
Approach: By irradiating a 50% area of the culture dish (half-field exposure), experimental dose-response curves for cell survival and residual DNA double-strand breaks (DSBs) were generated in prostate (DU145) and non-small cell lung cancer (H1299) cells. The oxygen enhancement ratio (OER) was determined from early DSB yields (corresponding to relative direct damage) and used to model the in- and out-of-field radiosensitivity. 
Main results: The developed integrated microdosimetric-kinetic (IMK) model successfully predicted the experimental dose responses for survival and lethal lesions, and provides a mechanistic interpretation that the probability of hits for releasing cell-killing signals is dependent on oxygen. This experimental and modelling study also suggests that residual DSBs correspond to logarithmic survival fraction (meaning lethal lesions) for in- and out-of-field cells. Our data suggest that the OER value determined using uniform-field exposure can be applied to predict the in- and out-of-field radiosensitivity of cells following exposure to intensity modulated beams. 
Significance: The developed IMK model facilitates a more precise understanding of intercellular signalling following exposure to intensity-modulated radiation fields.

Author Correction: Impact of the Lorentz force on electron track structure and early DNA damage yields in magnetic resonance-guided radiotherapy.
Yoshie Yachi, Takeshi Kai, Yusuke Matsuya, Yuho Hirata, Yuji Yoshii, Hiroyuki Date
Scientific reports, 13, 1, 2239, 2239, 08 Feb. 2023, [International Magazine]
English

An Analytical Method for Quantifying the Yields of DNA Double-Strand Breaks Coupled with Strand Breaks by γ-H2AX Focus Formation Assay Based on Track-Structure Simulation
Yoshie Yachi, Yusuke Matsuya, Yuji Yoshii, Hisanori Fukunaga, Hiroyuki Date, Takeshi Kai
International Journal of Molecular Sciences, 24, 2, 1386, 1386, MDPI AG, 10 Jan. 2023
Scientific journal, Complex DNA double-strand break (DSB), which is defined as a DSB coupled with additional strand breaks within 10 bp in this study, induced after ionizing radiation or X-rays, is recognized as fatal damage which can induce cell death with a certain probability. In general, a DSB site inside the nucleus of live cells can be experimentally detected using the γ-H2AX focus formation assay. DSB complexity is believed to be detected by analyzing the focus size using such an assay. However, the relationship between focus size and DSB complexity remains uncertain. In this study, using Monte Carlo (MC) track-structure simulation codes, i.e., an in-house WLTrack code and a Particle and Heavy Ion Transport code System (PHITS), we developed an analytical method for qualifying the DSB complexity induced by photon irradiation from the microscopic image of γ-H2AX foci. First, assuming that events (i.e., ionization and excitation) potentially induce DNA strand breaks, we scored the number of events in a water cube (5.03 × 5.03 × 5.03 nm3) along electron tracks. Second, we obtained the relationship between the number of events and the foci size experimentally measured by the γ-H2AX focus formation assay. Third, using this relationship, we evaluated the degree of DSB complexity induced after photon irradiation for various X-ray spectra using the foci size, and the experimental DSB complexity was compared to the results estimated by the well-verified DNA damage estimation model in the PHITS code. The number of events in a water cube was found to be proportional to foci size, suggesting that the number of events intrinsically related to DSB complexity at the DNA scale. The developed method was applicable to focus data measured for various X-ray spectral situations (i.e., diagnostic kV X-rays and therapeutic MV X-rays). This method would contribute to a precise understanding of the early biological impacts of photon irradiation by means of the γ-H2AX focus formation assay.

Initial yield of hydrated electron production from water radiolysis based on first-principles calculation
Takeshi Kai, Tomohiro Toigawa, Yusuke Matsuya, Yuho Hirata, Tomoya Tezuka, Hidetsugu Tsuchida, Akinari Yokoya
RSC Advances, 13, 11, 7076, 7086, Royal Society of Chemistry (RSC), 2023
Scientific journal, For water radiolysis, conventional simulation methods estimate free radical yields based on the cross-sections. Our results indicated that electron dynamic motion must be further solved to predict the initial yields of hydrated electrons.

放射線の挙動を原子サイズで計算できるPHITSの新機能　　　　　　　　　　　　　　　
小川達彦, 平田悠歩, 松谷悠佑, 甲斐健師
Isotope News, 784, 13, 16, Dec. 2022, [Peer-reviewed], [Invited]

Application of a simple DNA damage model developed for electrons to proton irradiation.
Yusuke Matsuya, Takeshi Kai, Alessio Parisi, Yuji Yoshii, Tatsuhiko Sato
Physics in medicine and biology, 67, 21, 31 Oct. 2022, [International Magazine]
English, Scientific journal, Proton beam therapy allows irradiating tumor volumes with reduced side effects on normal tissues with respect to conventional x-ray radiotherapy. Biological effects such as cell killing after proton beam irradiations depend on the proton kinetic energy, which is intrinsically related to early DNA damage induction. As such, DNA damage estimation based on Monte Carlo simulations is a research topic of worldwide interest. Such simulation is a mean of investigating the mechanisms of DNA strand break formations. However, past modellings considering chemical processes and DNA structures require long calculation times. Particle and heavy ion transport system (PHITS) is one of the general-purpose Monte Carlo codes that can simulate track structure of protons, meanwhile cannot handle radical dynamics simulation in liquid water. It also includes a simple model enabling the efficient estimation of DNA damage yields only from the spatial distribution of ionizations and excitations without DNA geometry, which was originally developed for electron track-structure simulations. In this study, we investigated the potential application of the model to protons without any modification. The yields of single-strand breaks, double-strand breaks (DSBs) and the complex DSBs were assessed as functions of the proton kinetic energy. The PHITS-based estimation showed that the DSB yields increased as the linear energy transfer (LET) increased, and reproduced the experimental and simulated yields of various DNA damage types induced by protons with LET up to about 30 keVμm-1. These results suggest that the current DNA damage model implemented in PHITS is sufficient for estimating DNA lesion yields induced after protons irradiation except at very low energies (below 1 MeV). This model contributes to evaluating early biological impacts in radiation therapy.

Implementation of the electron track-structure mode for silicon into PHITS for investigating the radiation effects in semiconductor devices
Yuho Hirata, Takeshi Kai, Tatsuhiko Ogawa, Yusuke Matsuya, Tatsuhiko Sato
Japanese Journal of Applied Physics, 61, 10, 106004, 106004, IOP Publishing, 01 Oct. 2022
Scientific journal, Abstract

In order to elucidate the mechanism of radiation effects in silicon (Si) devices, such as pulse-height defects and semiconductor soft errors, we developed an electron track-structure model dedicated to Si and implemented it into particle and heavy ion transport code system (PHITS). Then, we verified the accuracy of our developed model by comparing the ranges and depth-dose distributions of electrons in Si obtained from this study with corresponding experimental values and other simulated results. As an application of the model, we calculated the mean energies required to create an electron–hole pair in crystalline Si. Our calculated result agreed with the experimental data when the threshold energy for generating secondary electrons was set to 2.75 eV, consistent with the corresponding data deduced from past studies. This result suggested that the improved PHITS can contribute to the precise understanding of the mechanisms of radiation effects in Si devices.

Impact of the Lorentz force on electron track structure and early DNA damage yields in magnetic resonance-guided radiotherapy.
Yoshie Yachi, Takeshi Kai, Yusuke Matsuya, Yuho Hirata, Yuji Yoshii, Hiroyuki Date
Scientific reports, 12, 1, 16412, 16412, 30 Sep. 2022, [International Magazine]
English, Scientific journal, Magnetic resonance-guided radiotherapy (MRgRT) has been developed and installed in recent decades for external radiotherapy in several clinical facilities. Lorentz forces modulate dose distribution by charged particles in MRgRT; however, the impact of Lorentz forces on low-energy electron track structure and early DNA damage induction remain unclear. In this study, we estimated features of electron track structure and biological effects in a static magnetic field (SMF) using a general-purpose Monte Carlo code, particle and heavy ion transport code system (PHITS) that enables us to simulate low-energy electrons down to 1 meV by track-structure mode. The macroscopic dose distributions by electrons above approximately 300 keV initial energy in liquid water are changed by both perpendicular and parallel SMFs against the incident direction, indicating that the Lorentz force plays an important role in calculating dose within tumours. Meanwhile, DNA damage estimation based on the spatial patterns of atomic interactions indicates that the initial yield of DNA double-strand breaks (DSBs) is independent of the SMF intensity. The DSB induction is predominantly attributed to the secondary electrons below a few tens of eV, of which energy deposition patterns are not considerably affected by the Lorentz force. Our simulation study suggests that treatment planning for MRgRT can be made with consideration of only changed dose distribution.

Microdosimetry Study of Proton Quality Factor Using Analytic Model Calculations
Alexis Papadopoulos, Ioanna Kyriakou, Yusuke Matsuya, Sebastien Incerti, Ioannis A. Daglis, Dimitris Emfietzoglou
Applied Sciences, 12, 18, 8950, 8950, MDPI AG, 06 Sep. 2022
Scientific journal, The quality factor (Q) is formally linked to the stochastic (e.g., carcinogenic) risk of diverse ionizing radiations at low doses and/or low dose rates. Q can be a function of the non-stochastic physical quantity Linear Energy Transfer (LET) or the microdosimetric parameter lineal energy (y). These two physical quantities can be calculated either by Monte Carlo (MC) track-structure simulations or by analytic models. In this work, various generalized analytical models were utilized and combined to determine the proton lineal energy spectra in liquid water spheres of various sizes (i.e., 10–3000 nm diameter) over the proton energy range of 1–250 MeV. The calculated spectra were subsequently used within the Theory of Dual Radiation Action (TDRA) and the ICRU Report 40 microdosimetric methodologies to determine the variation of Q¯ with proton energy. The results revealed that the LET-based Q values underestimated the microdosimetric-based Q¯ values for protons with energy below ~100 MeV. At energies relevant to the Bragg peak region (<20–30 MeV), the differences were larger than 20–50%, while reaching 200–500% at ~5 MeV. It was further shown that the microdosimetric-based Q¯ values for protons below ~100 MeV were sensitive to the sphere size. Finally, condensed-phase effects had a very small (<5%) influence on the calculated microdosimetric-based Q¯ over the proton energy range considered here.

Microdosimetric modeling of relative biological effectiveness for skin reactions: Possible linkage between in vitro and in vivo data
Tatsuhiko Sato, Yusuke Matsuya, Nobuyuki Hamada
International Journal of Radiation Oncology*Biology*Physics, Elsevier BV, May 2022, [Peer-reviewed]
Scientific journal

Inflammatory Signaling and DNA Damage Responses after Local Exposure to an Insoluble Radioactive Microparticle
Yusuke Matsuya, Nobuyuki Hamada, Yoshie Yachi, Yukihiko Satou, Masayori Ishikawa, Hiroyuki Date, Tatsuhiko Sato
Cancers, 14, 4, 1045, 1045, 18 Feb. 2022, [Peer-reviewed], [Lead author]
English, Scientific journal

Features of accelerator-based neutron source for boron neutron capture therapy calculated by particle and heavy ion transport code system (PHITS)
Yusuke Matsuya, Tamon Kusumoto, Yoshie Yachi, Yuho Hirata, Misako Miwa, Masayori Ishikawa, Hiroyuki Date, Yosuke Iwamoto, Shigeo Matsuyama, Hisanori Fukunaga
AIP Advances, 12, 2, 025013, 025013, AIP Publishing, 01 Feb. 2022, [Peer-reviewed], [Lead author]
Scientific journal

Track-structure modes in particle and heavy ion transport code system (PHITS): application to radiobiological research
Yusuke Matsuya, Takeshi Kai, Tatsuhiko Sato, Tatsuhiko Ogawa, Yuho Hirata, Yuji Yoshii, Alessio Parisi, Thiansin Liamsuwan
International Journal of Radiation Biology, 98, 2, 148, 157, 01 Feb. 2022, [Peer-reviewed]
English, Scientific journal

Tumor radioresistance caused by radiation-induced changes of stem-like cell content and sub-lethal damage repair capability
Roman Fukui, Ryo Saga, Yusuke Matsuya, Kazuo Tomita, Yoshikazu Kuwahara, Kentaro Ohuchi, Tomoaki Sato, Kazuhiko Okumura, Hiroyuki Date, Manabu Fukumoto, Yoichiro Hosokawa
Scientific Reports, 12, 1, Springer Science and Business Media {LLC}, Dec. 2021, [Peer-reviewed]
English, Scientific journal, Abstract

Cancer stem-like cells (CSCs) within solid tumors exhibit radioresistance, leading to recurrence and distant metastasis after radiotherapy. To experimentally study the characteristics of CSCs, radioresistant cell lines were successfully established using fractionated X-ray irradiation. The fundamental characteristics of CSCs in vitro have been previously reported; however, the relationship between CSC and acquired radioresistance remains uncertain. To efficiently study this relationship, we performed both in vitro experiments and theoretical analysis using a cell-killing model. Four types of human oral squamous carcinoma cell lines, non-radioresistant cell lines (SAS and HSC2), and radioresistant cell lines (SAS-R and HSC2-R), were used to measure the surviving fraction after single-dose irradiation, split-dose irradiation, and multi-fractionated irradiation. The SAS-R and HSC2-R cell lines were more positive for one of the CSC marker aldehyde dehydrogenase activity than the corresponding non-radioresistant cell lines. The theoretical model analysis showed that changes in both the experimental-based ALDH (+) fractions and DNA repair efficiency of ALDH (−) fractions (i.e., sub-lethal damage repair) are required to reproduce the measured cell survival data of non-radioresistant and radioresistant cell lines. These results suggest that the enhanced cell recovery in SAS-R and HSC2-R is important when predicting tumor control probability in radiotherapy to require a long dose-delivery time; in other words, intensity-modulated radiation therapy is ideal. This work provides a precise understanding of the mechanism of radioresistance, which is induced after irradiation of cancer cells.

Development and validation of proton track-structure model applicable to arbitrary materials
Tatsuhiko Ogawa, Yuho Hirata, Yusuke Matsuya, Takeshi Kai
Scientific Reports, 11, 1, Dec. 2021, [Peer-reviewed]
English, Scientific journal

Track-structure mode for electrons, protons and carbon ions in the PHITS code　　　　　　　　　　　　　　　
Yusuke Matsuya, Takeshi Kai, Tatsuhiko Ogawa, Yuho Hirata, Tatsuhiko Sato
Hoshasen Kagaku, 112, 15, 20, Nov. 2021, [Peer-reviewed], [Invited], [Lead author]
Japanese

Model development for estimating effects of boron neutron capture therapy.　　　　　　　　　　　　　　　
Hisanori Fukunaga, Yusuke Matsuya
Radiation Biology Research Communications, 56, 2, 208, 223, Jun. 2021, [Peer-reviewed], [Invited]
Scientific journal

Oxygen enhancement ratios of cancer cells after exposure to intensity modulated x-ray fields: DNA damage and cell survival
Yusuke Matsuya, Stephen J McMahon, Karl T Butterworth, Shingo Naijo, Isshi Nara, Yoshie Yachi, Ryo Saga, Masayori Ishikawa, Tatsuhiko Sato, Hiroyuki Date, Kevin M Prise
Physics in Medicine & Biology, 66, 7, 075014, 075014, IOP Publishing, 07 Apr. 2021, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, Hypoxic cancer cells within solid tumours show radio-resistance, leading to malignant progression in fractionated radiotherapy. When prescribing dose to tumours under heterogeneous oxygen pressure with intensity-modulated radiation fields, intercellular signalling could have an impact on radiosensitivity between in-field and out-of-field (OF) cells. However, the impact of hypoxia on radio-sensitivity under modulated radiation intensity remains to be fully clarified. Here, we investigate the impact of hypoxia on in-field and OF radio-sensitivities using two types of cancer cells, DU145 and H1299. Using a nBIONIX hypoxic culture kit and a shielding technique to irradiate 50% of a cell culture flask, oxygen enhancement ratios for double-strand breaks (DSB) and cell death endpoints were determined. Thesein vitromeasurements indicate that hypoxia impacts OF cells, although the hypoxic impacts on OF cells for cell survival were dose-dependent and smaller compared to those for in-field and uniformly irradiated cells. These decreased radio-sensitivities of OF cells were shown as a consistent tendency for both DSB and cell death endpoints, suggesting that radiation-induced intercellular communication is of importance in advanced radiotherapy dose-distributions such as with intensity-modulated radiotherapy.

4-Methylumbelliferone administration enhances radiosensitivity of human fibrosarcoma by intercellular communication
Ryo Saga, Yusuke Matsuya, Rei Takahashi, Kazuki Hasegawa, Hiroyuki Date, Yoichiro Hosokawa
Scientific Reports, 11, 1, 8258, 8258, Springer Science and Business Media LLC, Apr. 2021, [Peer-reviewed], [International Magazine]
English, Scientific journal, Hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) is a candidate of radiosensitizers which enables both anti-tumour and anti-metastasis effects in X-ray therapy. The curative effects under such 4-MU administration have been investigated in vitro; however, the radiosensitizing mechanisms remain unclear. Here, we investigated the radiosensitizing effects under 4-MU treatment from cell experiments and model estimations. We generated experimental surviving fractions of human fibrosarcoma cells (HT1080) after 4-MU treatment combined with X-ray irradiation. Meanwhilst, we also modelled the pharmacological effects of 4-MU treatment and theoretically analyzed the synergetic effects between 4-MU treatment and X-ray irradiation. The results show that the enhancement of cell killing by 4-MU treatment is the greatest in the intermediate dose range of around 4 Gy, which can be reproduced by considering intercellular communication (so called non-targeted effects) through the model analysis. As supposed to be the involvement of intercellular communication in radiosensitization, the oxidative stress level associated with reactive oxygen species (ROS), which leads to DNA damage induction, is significantly higher by the combination of 4-MU treatment and irradiation than only by X-ray irradiation, and the radiosensitization by 4-MU can be suppressed by the ROS inhibitors. These findings suggest that the synergetic effects between 4-MU treatment and irradiation are predominantly attributed to intercellular communication and provide more efficient tumour control than conventional X-ray therapy.

Verification of KURBUC-based ion track structure mode for proton and carbon ions in the PHITS code
Yusuke Matsuya, Takeshi Kai, Tatsuhiko Sato, Thiansin Liamsuwan, Kohei Sasaki, Hooshang Nikjoo
Physics in Medicine & Biology, 66, 6, 06NT02, 06NT02, IOP Publishing, 21 Mar. 2021, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, The Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo radiation transport simulation code. It has the ability to handle diverse particle types over a wide range of energy. The latest PHITS development enables the generation of track structure for proton and carbon ions (1H+,12C6+) based on the algorithms in the KURBUC code, which is considered as one of the most verified track-structure codes worldwide. This ion track-structure mode is referred to as the PHITS-KURBUC mode. In this study, the range, radial dose distributions, and microdosimetric distributions were calculated using the PHITS-KURBUC mode. Subsequently, they were compared with the corresponding data obtained from the original KURBUC and from other studies. These comparative studies confirm the successful inclusion of the KURBUC code in the PHITS code. As results of the synergistic effect between the macroscopic and microscopic radiation transport codes, this implementation enabled the detailed calculation of the microdosimetric and nanodosimetric quantities under complex radiation fields, such as proton beam therapy with the spread-out Bragg peak.

Development of a new microdosimetric biological weighting function for the RBE10 assessment in case of the V79 cell line exposed to ions from 1H to 238U
Alessio Parisi, Tatsuhiko Sato, Yusuke Matsuya, Yuki Kase, Giulio Magrin, Claudio Verona, Linh Tran, Anatoly Rosenfeld, Anna Bianchi, Pawel Olko, Lara Struelens, Filip Vanhavere
Physics in Medicine & Biology, 65, 23, 235010, 235010, {IOP} Publishing, 04 Dec. 2020, [Peer-reviewed]
Scientific journal

Relation between biomolecular dissociation and energy of secondary electrons generated in liquid water by fast heavy ions
Hidetsugu Tsuchida, Takeshi Kai, Kensei Kitajima, Yusuke Matsuya, Takuya Majima, Manabu Saito
The European Physical Journal D, 74, 10, Springer Science and Business Media {LLC}, Oct. 2020, [Peer-reviewed]
English, Scientific journal

Radiation Safety and Public Health for Radiological Professionals: Meeting Report on The 5th Educational Symposium on Radiation and Health (ESRAH) by Young Scientists in 2018　　　　　　　　　　　　　　　
Hiroko Yamashina, Marin Terashima, Joma Oikawa, Shingo Naijo, Tamao Miyao, Yoshie Yachi, Yusuke Matsuya, Masaru Yamaguchi, Takakiyo Tsujiguchi, Ryo Saga, Hu Jun, Goh Valerie, Swee Ting, Toshiya Nakamura, Yoichiro Hosokawa, Hiroyuki Date
Radiation Environment and Medicine, 10, 1, 48, 54, Jul. 2020

Implications of radiation microdosimetry for accelerator-based boron neutron capture therapy: A radiobiological perspective.
Hisanori Fukunaga, Yusuke Matsuya, Koichi Tokuuye, Motoko Omura
British Journal of Radiology, 93, 20200311, British Institute of Radiology, 06 May 2020, [Peer-reviewed], [International Magazine]
English, Scientific journal, Boron neutron capture therapy (BNCT) has great potential to selectively destroy cancer cells while sparing surrounding normal cells. The basic concept of BNCT was developed in the 1930s, but it has not yet been commonly used in clinical practice, even although there is now a large number of experimental and translational studies demonstrating its marked therapeutic potential. With the development of neutron accelerators that can be installed in medical institutions, accelerator-based BNCT is expected to become available at several medical institutes around the world in the near future. In this commentary, from the point of view of radiation microdosimetry, we discuss the biological effects of BNCT, especially the underlying mechanisms of compound biological effectiveness. Radiobiological perspectives provide insight into the effectiveness of BNCT in creating a synergy effect in the field of clinical oncology.

A Model for Estimating Dose-Rate Effects on Cell-Killing of Human Melanoma after Boron Neutron Capture Therapy.
Yusuke Matsuya, Hisanori Fukunaga, Motoko Omura, Hiroyuki Date
Cells, 9, 5, 1117, Multidisciplinary Digital Publishing Institute, 30 Apr. 2020, [Peer-reviewed], [International Magazine]
English, Scientific journal, Boron neutron capture therapy (BNCT) is a type of radiation therapy for eradicating tumor cells through a 10B(n,α)7Li reaction in the presence of 10B in cancer cells. When delivering a high absorbed dose to cancer cells using BNCT, both the timeline of 10B concentrations and the relative long dose-delivery time compared to photon therapy must be considered. Changes in radiosensitivity during such a long dose-delivery time can reduce the probability of tumor control; however, such changes have not yet been evaluated. Here, we propose an improved integrated microdosimetric-kinetic model that accounts for changes in microdosimetric quantities and dose rates depending on the 10B concentration and investigate the cell recovery (dose-rate effects) of melanoma during BNCT irradiation. The integrated microdosimetric-kinetic model used in this study considers both sub-lethal damage repair and changes in microdosimetric quantities during irradiation. The model, coupled with the Monte Carlo track structure simulation code of the Particle and Heavy Ion Transport code System, shows good agreement with in vitro experimental data for acute exposure to 60Co γ-rays, thermal neutrons, and BNCT with 10B concentrations of 10 ppm. This indicates that microdosimetric quantities are important parameters for predicting dose-response curves for cell survival under BNCT irradiations. Furthermore, the model estimation at the endpoint of the mean activation dose exhibits a reduced impact of cell recovery during BNCT irradiations with high linear energy transfer (LET) compared to 60Co γ-rays irradiation with low LET. Throughout this study, we discuss the advantages of BNCT for enhancing the killing of cancer cells with a reduced dose-rate dependency. If the neutron spectrum and the timelines for drug and dose delivery are provided, the present model will make it possible to predict radiosensitivity for more realistic dose-delivery schemes in BNCT irradiations.

A theoretical cell-killing model to evaluate oxygen enhancement ratios at DNA damage and cell survival endpoints in radiation therapy
Yusuke Matsuya, Tatsuhiko Sato, Rui Nakamura, Shingo Naijo, Hiroyuki Date
Physics in Medicine & Biology, 65, 9, 095006, 095006, {IOP} Publishing, 28 Apr. 2020, [Peer-reviewed]
Scientific journal

A Simplified Cluster Analysis of Electron Track Structure for Estimating Complex DNA Damage Yields
Yusuke Matsuya, Toshiaki Nakano, Takeshi Kai, Naoya Shikazono, Ken Akamatsu, Yuji Yoshii, Tatsuhiko Sato
International Journal of Molecular Sciences, 21, 5, 1701, 1701, 02 Mar. 2020, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Verification of dose estimation of Auger electrons emitted from Cu-64 using a combination of FNTD measurements and Monte Carlo simulations
Tamon Kusumoto, Yusuke Matsuya, Kentaro Baba, Ryo Ogawara, Mark S. Akselrod, Jonathan Harrison, Vasiliy Fomenko, Takeshi Kai, Masayori Ishikawa, Sumitaka Hasegawa, Satoshi Kodaira
Radiation Measurements, 132, Mar. 2020, [Peer-reviewed]
Scientific journal

DNA damage induction during localized chronic exposure to an insoluble radioactive microparticle
Yusuke Matsuya, Yukihiko Satou, Nobuyuki Hamada, Hiroyuki Date, Masayori Ishikawa, Tatsuhiko Sato
Scientific Reports, 9, 1, Springer Science and Business Media LLC, Dec. 2019, [Peer-reviewed]
English, Scientific journal

Track Structure Study for Energy Dependency of Electrons and X-rays on DNA Double-Strand Break Induction
Yachi T, Yoshii Y, Matsuya Y, Mori R, Oikawa J, Date H
Scientific Reports, 9, 17649, 17649, 17649, Nov. 2019, [Peer-reviewed], [International Magazine]
English, Scientific journal, Radiation weighting factor wR for photons and electrons has been defined as unity independently of the energy of the particles. However, the biological effects depend on the incident energies according to in vitro experimental data. In this study, we have quantified the energy concentration along electron tracks in terms of dose-mean lineal energy (yD) on chromosome (micro-meter) and DNA (nano-meter) order scales by Monte Carlo simulations, and evaluated the impact of photon energies on DNA double-strand break (DNA-DSB) induction from an experimental study of irradiated cells. Our simulation result shows that the yD values for diagnostic X-rays (60-250 kVp) are higher than that for therapeutic X-rays (linac 6 MV), which agrees well with the tissue equivalent proportional counter (TEPC) measurements. The relation between the yD values and the numbers of γ-H2AX foci for various photon energy spectra suggests that low energy X-rays induce DNA-DSB more efficiently than higher energy X-rays even at the same absorbed dose (e.g., 1.0 Gy). The relative biological effectiveness based on DNA-DSBs number (RBEDSB) is proportionally enhanced as the yD value increases, demonstrating that the biological impact of the photon irradiation depends on energy concentration along radiation tracks of electrons produced in the bio-tissues. Ultimately, our study implies that the value of wR for photons varies depending on their energies.

Modeling of yield estimation for DNA strand breaks based on Monte Carlo simulations of electron track structure in liquid water
Yusuke Matsuya, Takeshi Kai, Yuji Yoshii, Yoshie Yachi, Shingo Naijo, Hiroyuki Date, Tatsuhiko Sato
Journal of Applied Physics, 126, 12, 124701, 124701, {AIP} Publishing, 28 Sep. 2019, [Peer-reviewed]
English, Scientific journal

Intensity Modulated Radiation Fields Induce Protective Effects and Reduce Importance of Dose-Rate Effects.
Matsuya Y, McMahon SJ, Ghita M, Yoshii Y, Sato T, Date H, Prise KM
Scientific Reports, 9, 9483, 9483, 9483, Jul. 2019, [Peer-reviewed], [International Magazine]
English, Scientific journal, In advanced radiotherapy, intensity modulated radiation fields and complex dose-delivery are utilized to prescribe higher doses to tumours. Here, we investigated the impact of modulated radiation fields on radio-sensitivity and cell recovery during dose delivery. We generated experimental survival data after single-dose, split-dose and fractionated irradiation in normal human skin fibroblast cells (AGO1522) and human prostate cancer cells (DU145). The dose was delivered to either 50% of the area of a T25 flask containing the cells (half-field) or 100% of the flask (uniform-field). We also modelled the impact of dose-rate effects and intercellular signalling on cell-killing. Applying the model to the survival data, it is found that (i) in-field cell survival under half-field exposure is higher than uniform-field exposure for the same delivered dose; (ii) the importance of sub-lethal damage repair (SLDR) in AGO1522 cells is reduced under half-field exposure; (iii) the yield of initial DNA lesions measured with half-field exposure is smaller than that with uniform-field exposure. These results suggest that increased cell survival under half-field exposure is predominantly attributed not to rescue effects (increased SLDR) but protective effects (reduced induction of initial DNA lesions). In support of these protective effects, the reduced DNA damage leads to modulation of cell-cycle dynamics, i.e., less G1 arrest 6 h after irradiation. These findings provide a new understanding of the impact of dose-rate effects and protective effects measured after modulated field irradiation.

Analysis of the high-dose-range radioresistance of prostate cancer cells, including cancer stem cells, based on a stochastic model.
Ryo Saga, Yusuke Matsuya, Rei Takahashi, Kazuki Hasegawa, Hiroyuki Date, Yoichiro Hosokawa
Journal of radiation research, 60, 3, 298, 307, 01 May 2019, [Peer-reviewed], [International Magazine]
English, Scientific journal, In radiotherapy, cancer stem cells (CSCs) are well recognized as one of the radioresistant cell types. Even in a small subpopulation, CSCs may have an influence on tumor control probability, represented by cell killing after irradiation. However, the relationship between the percentage content of CSCs and the cell survival dose-response curve has not yet been quantitatively clarified. In this study, we developed a cell-killing model for two cell populations (CSCs and progeny cells) to predict the surviving fractions, and compared it with the conventional linear-quadratic (LQ) model. Three prostate cancer cell lines (DU145, PC3 and LNCaP) were exposed to X-rays at doses ranging from 0 to 10 Gy. After the irradiation, we performed clonogenic survival assays to generate the cell survival curves, and carried out flow-cytometric analyses to estimate the percentage content of CSCs for each cell line. The cell survival curves for DU145 cells and PC3 cells seemed not to follow the conventional LQ model in the high dose range (>8 Gy). However, the outputs of the developed model agreed better with the experimental cell survival curves than those of the LQ model. The percentage content of CSCs predicted by the developed model was almost coincident with the measured percentage content for both DU145 cells and PC3 cells. The experiments and model analyses indicate that a small subpopulation of radioresistant CSCs has lower radiosensitivity in the high-dose range, which may lessen the clinical outcome for patients with prostate cancer after high-dose radiation therapy.

Meeting Report on "The 4th Educational Symposium on Radiation and Health (ESRAH) by Young Scientists in 2017"
Saga R, Tsujiguchi T, Yamaguchi M, Fukushi Y, Fujishima Y, Matsuya Y, Oikawa J, Terashima M, Date H, Nakamura T, Hosokawa Y
Radiation environment and medicine : covering a broad scope of topics relevant to environmental and medical radiation research, 7, 2, 121, 124, Hirosaki University Press, Aug. 2018, [Peer-reviewed]
English, Scientific journal

Investigation of dose-rate effects and cell-cycle distribution under protracted exposure to ionizing radiation for various dose-rates.
Yusuke Matsuya, Stephen J McMahon, Kaori Tsutsumi, Kohei Sasaki, Go Okuyama, Yuji Yoshii, Ryosuke Mori, Joma Oikawa, Kevin M Prise, Hiroyuki Date
Scientific reports, 8, 1, 8287, 8287, 29 May 2018, [Peer-reviewed], [International Magazine]
English, Scientific journal, During exposure to ionizing radiation, sub-lethal damage repair (SLDR) competes with DNA damage induction in cultured cells. By virtue of SLDR, cell survival increases with decrease of dose-rate, so-called dose-rate effects (DREs). Here, we focused on a wide dose-rate range and investigated the change of cell-cycle distribution during X-ray protracted exposure and dose-response curves via hybrid analysis with a combination of in vitro experiments and mathematical modelling. In the course of flow-cytometric cell-cycle analysis and clonogenic assays, we found the following responses in CHO-K1 cells: (1) The fraction of cells in S phase gradually increases during 6 h exposure at 3.0 Gy/h, which leads to radio-resistance. (2) Slight cell accumulation in S and G2/M phases is observed after exposure at 6.0 Gy/h for more than 10 hours. This suggests that an increase of SLDR rate for cells in S phase during irradiation may be a reproducible factor to describe changes in the dose-response curve at dose-rates of 3.0 and 6.0 Gy/h. By re-evaluating cell survival for various dose-rates of 0.186-60.0 Gy/h considering experimental-based DNA content and SLDR, it is suggested that the change of S phase fraction during irradiation modulates the dose-response curve and is possibly responsible for some inverse DREs.

Estimation of the radiation-induced DNA double-strand breaks number by considering cell cycle and absorbed dose per cell nucleus
Ryosuke Mori, Yusuke Matsuya, Yuji Yoshii, Hiroyuki Date
Journal of Radiation Research, 59, 3, 253, 260, Oxford University Press, 01 May 2018, [Peer-reviewed]
English, Scientific journal

Integrated Modelling of Cell Responses after Irradiation for DNA-Targeted Effects and Non-Targeted Effects.
Yusuke Matsuya, Kohei Sasaki, Yuji Yoshii, Go Okuyama, Hiroyuki Date
Scientific reports, 8, 1, 4849, 4849, 19 Mar. 2018, [Peer-reviewed], [International Magazine]
English, Scientific journal, Intercellular communication after ionizing radiation exposure, so-called non-targeted effects (NTEs), reduces cell survival. Here we describe an integrated cell-killing model considering NTEs and DNA damage along radiation particle tracks, known as DNA-targeted effects (TEs) based on repair kinetics of DNA damage. The proposed model was applied to a series of experimental data, i.e., signal concentration, DNA damage kinetics, cell survival curve and medium transfer bystander effects (MTBEs). To reproduce the experimental data, the model considers the following assumptions: (i) the linear-quadratic (LQ) function as absorbed dose to express the hit probability to emit cell-killing signals, (ii) the potentially repair of DNA lesions induced by NTEs, and (iii) lower efficiency of repair for the damage in NTEs than that in TEs. By comparing the model results with experimental data, we found that signal-induced DNA damage and lower repair efficiency in non-hit cells are responsible for NTE-related repair kinetics of DNA damage, cell survival curve with low-dose hyper-radiosensitivity (HRS) and MTBEs. From the standpoint of modelling, the integrated cell-killing model with the LQ relation and a different repair function for NTEs provide a reasonable signal-emission probability and a new estimation of low-dose HRS linked to DNA repair efficiency.

Markov chain Monte Carlo analysis for the selection of a cell-killing model under high-dose-rate irradiation
Yusuke Matsuya, Takaaki Kimura, Hiroyuki Date
MEDICAL PHYSICS, 44, 10, 5522, 5532, Oct. 2017, [Peer-reviewed]
English, Scientific journal

Educational Activity for the Radiation Emergency System in the Northern Part of Japan: Meeting Report on "The 3rd Educational Symposium on Radiation and Health (ESRAH) by Young Scientists in 2016''
Yusuke Matsuya, Takakiyo Tsujiguchi, Masaru Yamaguchi, Takaaki Kimura, Ryosuke Mori, Ryota Yamada, Ryo Saga, Yohei Fujishima, Hiroyuki Date
RADIATION RESEARCH, 187, 6, 641, 646, Jun. 2017, [Peer-reviewed]
English

Modeling cell survival and change in amount of DNA during protracted irradiation
Yusuke Matsuya, Kaori Tsutsumi, Kohei Sasaki, Yuji Yoshii, Takaaki Kimura, Hiroyuki Date
JOURNAL OF RADIATION RESEARCH, 58, 3, 302, 312, May 2017, [Peer-reviewed]
English, Scientific journal

Inorganic polyphosphate enhances radio-sensitivity in a human non-small cell lung cancer cell line, H1299
Kaori Tsutsumi, Yusuke Matsuya, Tomoki Sugahara, Manami Tamura, Satoshi Sawada, Sagiri Fukura, Hisashi Nakano, Hiroyuki Date
Tumor Biology, 39, 6, 1010428317705033, SAGE Publications Ltd, 01 Jan. 2017, [Peer-reviewed]
English, Scientific journal

Report on the 2nd Educational Symposium on RADIATION AND HEALTH by Young Scientists (ESRAH2015)
Tsujiguchi Takakiyo, Nanashima Naoki, Chiba Mitsuru, Terashima Shingo, Fujishima Yohei, Matsuya Yusuke, Kwon Jihun, Nakamura Toshiya
Radiation environment and medicine : covering a broad scope of topics relevant to environmental and medical radiation research, 5, 1, 65, 71, Hirosaki University Press, Mar. 2016, [Peer-reviewed]
Japanese, Scientific journal

Cluster analysis for the probability of DSB site induced by electron tracks
Y. Yoshii, K. Sasaki, Y. Matsuya, H. Date
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 350, 1, 55, 59, May 2015, [Peer-reviewed]
English, Scientific journal

The Report of the 2nd Educational Symposium on Radiation and Health by Young Scientists (ESRAH2015)
Tsujiguchi Takakiyo
Japanese Journal of Radiological Technology, 71, 11, 1132, 1137, Japanese Society of Radiological Technology, 2015
Japanese

Evaluation of the cell survival curve under radiation exposure based on the kinetics of lesions in relation to dose-delivery time
Yusuke Matsuya, Kaori Tsutsumi, Kohei Sasaki, Hiroyuki Date
JOURNAL OF RADIATION RESEARCH, 56, 1, 90, 99, Jan. 2015, [Peer-reviewed]
English, Scientific journal

Quantitative estimation of DNA damage by photon irradiation based on the microdosimetric-kinetic model
Yusuke Matsuya, Yosuke Ohtsubo, Kaori Tsutsumi, Kohei Sasaki, Rie Yamazaki, Hiroyuki Date
JOURNAL OF RADIATION RESEARCH, 55, 3, 484, 493, May 2014, [Peer-reviewed]
English, Scientific journal

Dose calculation for 320-row ADCT by using PMMA phantom-consideration of heel effect-
寺嶋真凛, 溝延数房, 松谷悠佑, 伊達広行, 北海道放射線技術雑誌(Web), 86, 2019

診療用X線によって生じる複雑なDNA二本鎖切断数の推定　　　　　　　　　　　　　　　
吉井 勇治, 松谷 悠佑, 佐々木 恒平, 森 諒輔, 伊達 広行, 北海道放射線技術雑誌, 82, 45, 46, Mar. 2017
(公社)日本放射線技術学会-北海道部会, Japanese

診断用X線によって生じる複雑なDNA二本鎖切断数の推定　　　　　　　　　　　　　　　
吉井 勇治, 松谷 悠佑, 佐々木 恒平, 森 諒輔, 伊達 広行, 北海道放射線技術雑誌, 81, 126, 126, Oct. 2016
(公社)日本放射線技術学会-北海道部会, Japanese

放射線の長時間照射中における細胞周期と放射線感受性の解析　　　　　　　　　　　　　　　
松谷 悠佑, 吉井 勇治, 堤 香織, 伊達 広行, 森 諒輔, 佐々木 恒平, 及川 青亮, 北海道放射線技術雑誌, 81, 127, 127, Oct. 2016
(公社)日本放射線技術学会-北海道部会, Japanese

標的・非標的効果を考慮した低線量X線被ばく後の細胞生存率モデル　　　　　　　　　　　　　　　
松谷 悠佑, 佐々木 恒平, 吉井 勇治, 木村 尭朗, 伊達 広行, 北海道放射線技術雑誌, 81, 128, 128, Oct. 2016
(公社)日本放射線技術学会-北海道部会, Japanese

計算シミュレーションによる放射線生物研究 照射・非照射細胞混在環境を模擬した確率的モデルによる細胞応答に関する研究　　　　　　　　　　　　　　　
佐々木 恒平, 松谷 悠佑, 吉井 勇治, 伊達 広行, 日本放射線影響学会大会講演要旨集, 59回, 10, 10, Oct. 2016
(一社)日本放射線影響学会, Japanese

Non-Targeted Effectを含めた細胞生存率に対する数理モデルの開発　　　　　　　　　　　　　　　
松谷 悠佑, 佐々木 恒平, 吉井 勇治, 伊達 広行, 日本放射線影響学会大会講演要旨集, 59回, 1, 1, Oct. 2016
(一社)日本放射線影響学会, Japanese

Participation/Dispatch Reports on International Conferences (Held in Japan) in 2014
Matsuya Yusuke, Shimizu Yoichiro, Kimata Hirona, Kato Hideki, Takenaga Tomomi, Takegami Kazuki, Hirosawa Ayaka, Yabe Hitoshi, Ito Yuya, Japanese Journal of Radiological Technology, 71, 4, 391, 401, 2015
Japanese Society of Radiological Technology, Japanese

微視的エネルギー付与の空間分布が及ぼすDNA二本鎖切断の誘導への影響
YOSHII YUJI, MATSUYA YUSUKE, SASAKI KOHEI, DATE HIROYUKI, 日本放射線技術学会雑誌, 70, 9, 986, 986, 20 Sep. 2014
(公社)日本放射線技術学会, Japanese

線量率の違いを考慮した細胞生存率モデルの有用性
MATSUYA YUSUKE, SASAKI KOHEI, TSUTSUMI KAORI, DATE HIROYUKI, 北海道放射線技術雑誌, 75, 75, 135, 135, 25 Oct. 2013
(公社)日本放射線技術学会-北海道部会, Japanese

モンテカルロ法を用いた23kVpX線の生物効果比の推定　　　　　　　　　　　　　　　
吉井 勇治, 佐々木 恒平, 三浦 貴智, 松谷 悠佑, 伊達 広行, 日本放射線影響学会大会講演要旨集, 56回, 97, 97, Oct. 2013
(一社)日本放射線影響学会, Japanese

放射線によるDNA損傷の定量的モデル解析と生物学的効果比
MATSUYA YUSUKE, OTSUBO YOSUKE, TSUTSUMI KAORI, YAMAZAKI RIE, SASAKI KOHEI, DATE HIROYUKI, 日本放射線影響学会大会講演要旨集, 56th, 97, 97, 01 Oct. 2013
(一社)日本放射線影響学会, Japanese

コンフルエント単層細胞環境における放射線誘発バイスタンダー効果のシミュレーション
SASAKI KOHEI, MATSUYA YUSUKE, TSUTSUMI KAORI, ITO AKIO, DATE HIROYUKI, 日本放射線影響学会大会講演要旨集, 56th, 111, 111, 01 Oct. 2013
(一社)日本放射線影響学会, Japanese

モンテカルロ法を用いた28kVpX線の生物効果比の推定
YOSHII YUJI, SASAKI KOHEI, MIURA TAKATOMO, MATSUYA YUSUKE, DATE HIROYUKI, 日本放射線影響学会大会講演要旨集, 56th, 97, 01 Oct. 2013
Japanese

ラジカル挙動計算コードPHITS-Chemの計算性能向上に関する研究　　　　　　　　　　　　　　　
吉井勇治, 松谷悠佑
日本保健物理学会第58回研究発表会, Japanese, Poster presentation
18 Dec. 2025 - 20 Dec. 2025

放射線挙動解析コードPHITS～細胞内ミクロ線量解析と治療効果の評価　　　　　　　　　　　　　　　
松谷悠佑
日本薬学会（北陸支部）講演, 25 Nov. 2025, Japanese, Public discourse
[Invited]

Cellular Responses of Human Lens Epithelial Cells and Its Dose-Rate Effects　　　　　　　　　　　　　　　
Y. Matsuya, T. Sato, N. Hamada
The 68th Annual Meeting of the Japanese Radiation Research Society/The 6th Asian Congress of Radiation Research, 25 Oct. 2025, English, Public symposium
23 Oct. 2025 - 26 Oct. 2025, [Invited]

Toward the evaluation of radiation weighting factors for tissue reactions based on microdosimetric RBE modeling　　　　　　　　　　　　　　　
T. Sato, Y. Matsuya, N. Hamada
The 68th Annual Meeting of the Japanese Radiation Research Society/The 6th Asian Congress of Radiation Research, 25 Oct. 2025, English, Public symposium
23 Oct. 2025 - 26 Oct. 2025, [Invited]

Investigation of the oxygen effects on the side population cells derived from prostate cancer cells using a cell-killing model considering heterogeneous radiosensitivity　　　　　　　　　　　　　　　
R. Saga, K. Iwamori, Y. Matsuya
The 68th Annual Meeting of the Japanese Radiation Research Society/The 6th Asian Congress of Radiation Research, 24 Oct. 2025, English, Poster presentation
23 Oct. 2025 - 26 Oct. 2025

Track-Structure Mode and Chemical Code for Simulating Atomic Collisions and Water Radiolysis in PHITS version 3.35　　　　　　　　　　　　　　　
Y. Matsuya
10th International Symposium of Quantum Beam Science at Ibaraki University (ISQBS2025), 10 Oct. 2025, English, Invited oral presentation
09 Oct. 2025 - 10 Oct. 2025, [Invited]

Monte Carlo simulation code for predicting temperature dependence of chemical products by water radiolysis　　　　　　　　　　　　　　　
M. Baba, Y. Yoshii, Y. Wang, Y. Matsuya
The 12th meeting of educational symposium of radiation and health (ESRAH 2025), 13 Sep. 2025, English, Poster presentation
13 Sep. 2025 - 14 Sep. 2025

Dose Calculation for Evaluating Biological Effects by Auger Electron-Emitting Radionuclides　　　　　　　　　　　　　　　
H. Nendai, Y. Wang, Y. Matsuya
The 12th meeting of educational symposium of radiation and health (ESRAH 2025), 13 Sep. 2025, English, Poster presentation
13 Sep. 2025 - 14 Sep. 2025

信頼性向上や飛跡構造解析モデルなどのPHITSの最新の開発状況（3）飛跡構造解析モデルの各種解析への応用　　　　　　　　　　　　　　　
平田悠歩, 松谷悠佑, 小川達彦, 甲斐健師, 佐藤達彦
日本原子力学会 2025年秋の大会, 10 Sep. 2025, Japanese, Oral presentation
10 Sep. 2025 - 12 Sep. 2025

Track-structure mode and DNA damage estimation in PHITS ver. 3.35　　　　　　　　　　　　　　　
Y. Matsuya
29th International Symposium on Ion-Atom Collisions (ISIAC2025), 27 Jul. 2025, English, Nominated symposium
25 Jul. 2025 - 27 Jul. 2025, [Invited]

Analysis of quenching effects in CaF₂:Ce using PHITS track-structure simulation　　　　　　　　　　　　　　　
Y. Hirata, T. Kai, T. Ogawa, Y. Matsuya, T. Sato, K. Watanabe, T. Kato, N. Kawaguchi, T. Yanagida
21st International Conference on Solid State Dosimetry (SSD-21)
08 Jun. 2025 - 13 Jun. 2025

Development of track-structure mode in PHITS and its application　　　　　　　　　　　　　　　
Y. Hirata, T. Kai, T. Ogawa, Y. Matsuya, T. Sato
The 2nd EGS5-Geant4-PHITS joint research congress, 16 May 2025, Japanese
15 May 2025 - 16 May 2025

DNA damage estimation based on PHITS track-structure simulation　　　　　　　　　　　　　　　
Y. Matsuya, K. Akamatsu, T. Ogawa, T. Nakano, N. Shikazono, T. Sato
The 2nd EGS5-Geant4-PHITS joint research congress, 16 May 2025, Japanese
15 May 2025 - 16 May 2025

Track-structure and water-radiolysis simulation in PHITS　　　　　　　　　　　　　　　
Yusuke Matsuya
PHITS workshop 2025, 18 Feb. 2025, English, Oral presentation
18 Feb. 2025 - 21 Feb. 2025, [Invited]

飛跡構造解析計算に基づく DNA 損傷・化学モデルの現状　　　　　　　　　　　　　　　
松谷悠佑
放射線安全フォーラム 第85回放射線防護研究会, 07 Dec. 2024, Japanese, Invited oral presentation
07 Dec. 2024 - 07 Dec. 2024, [Invited]

Observing the damage to biomolecules induced by ion beams in liquid jets　　　　　　　　　　　　　　　
T. Tsuchida, T. Ohta, N. Uno, A. Tachibana, T. Kai, Y. Matsuya, T. Sekikawa, T. Majima, M. Saito
ICACS & SHIM 2024, English
24 Nov. 2024 - 29 Nov. 2024

ポリビニルアルコール製剤を使用したホウ素中性子捕捉療法における治療効果の推定　　　　　　　　　　　　　　　
亀山栞里, 松谷悠佑
日本放射線技術学会 第80回北海道部会秋季大会, 24 Nov. 2024, Japanese, Oral presentation
23 Nov. 2024 - 24 Nov. 2024

α線標的アイソトープ治療における微視的エネルギー付与解析と治療効果　　　　　　　　　　　　　　　
佐藤花凜, 松谷悠佑
日本放射線技術学会 第80回北海道部会秋季大会, 24 Nov. 2024, Japanese, Oral presentation
23 Nov. 2024 - 24 Nov. 2024

陽子線および炭素線治療における水の放射線分解を予測するシミュレーションコードの開発　　　　　　　　　　　　　　　
伊藤幸音, 吉井勇治, 松谷悠佑
日本放射線技術学会 第80回北海道部会秋季大会, 24 Nov. 2024, Japanese, Oral presentation
23 Nov. 2024 - 24 Nov. 2024

電離したDNA分子の電子状態計算シミュレーション　　　　　　　　　　　　　　　
関川卓也, 松谷悠佑, 川井弘之, ファンボンジュ, 石坂優人, 佐藤達彦, 甲斐健師
日本放射線影響学会第67回大会, 25 Sep. 2024, Japanese, Invited oral presentation
25 Sep. 2024 - 28 Sep. 2024, [Invited]

MR リニアック放射線治療における物理的および生物学的影響を評価するための電子線のモンテカルロ飛跡構造シミュレーション　　　　　　　　　　　　　　　
松谷悠佑, 谷内淑惠, 甲斐健師
日本放射線影響学会第67回大会, 25 Sep. 2024, Japanese, Invited oral presentation
25 Sep. 2024 - 28 Sep. 2024, [Invited]

Estimation of biological effects after irradiation with alpha particles in targeted radionuclide therapy　　　　　　　　　　　　　　　
K. Satou, Y. Matsuya
The 11th meeting of educational symposium of radiation and health (ESRAH), 22 Sep. 2024, English, Poster presentation
21 Sep. 2024 - 22 Sep. 2024

Evaluation of boron uptake and relative biological effectiveness in boron neutron capture therapy　　　　　　　　　　　　　　　
S. Kameyama, Y. Matsuya
The 11th meeting of educational symposium of radiation and health (ESRAH), 21 Sep. 2024, English, Poster presentation
21 Sep. 2024 - 22 Sep. 2024

Monte Carlo simulation code for simulating chemical products by water radiolysis for evaluating biological effects　　　　　　　　　　　　　　　
Y. Ito, Y. Yoshii, T. Ogawa, T. Kai, Y. Matsuya
The 11th meeting of educational symposium of radiation and health (ESRAH), 21 Sep. 2024, English, Poster presentation
21 Sep. 2024 - 22 Sep. 2024

放射線輸送計算コードPHITSにおける化学コードの最新動向　　　　　　　　　　　　　　　
松谷 悠佑
第4回二次電子研究会, 12 Jul. 2024, Japanese, Invited oral presentation
12 Jul. 2024, [Invited]

放射線誘起正孔がもたらすDNAの分子構造と電子状態変化の第一原理計算II　　　　　　　　　　　　　　　
関川卓也, Hwang Beomju, 石坂優人, 松谷悠佑, 川井弘之, 大野義章, 佐藤達彦, 甲斐健師
日本物理学会 2024年春季大会, Mar. 2024
18 Mar. 2024 - 21 Mar. 2024

飛跡構造解析によるナノ規模分解能の放射線挙動計算　　　　　　　　　　　　　　　
小川達彦, 平田悠歩, 松谷悠佑, 甲斐健師
日本金属学会 2024年春季大会, Mar. 2024
12 Mar. 2024 - 15 Mar. 2024, [Invited]

放射線生物影響の最初期過程に関する計算機シミュレーション―DNAの放射線損傷による電子状態への影響―　　　　　　　　　　　　　　　
関川卓也, 松谷悠佑, ファン ボンジュ, 石坂優人, 大野義章, 佐藤達彦, 甲斐健師
第3回 日本量子医科学会学術大会, 08 Dec. 2023
[Invited]

放射線生物影響の最初期過程に関する計算機シミュレーション―DNA損傷の直接効果と間接効果―　　　　　　　　　　　　　　　
甲斐健師, 樋川智洋, 松谷悠佑, 平田悠歩, 手塚智哉, 土田秀次, 伊東祐真, 横谷明徳
第3回 日本量子医科学会学術大会, 08 Dec. 2023
[Invited]

PHITSを用いた口腔内金属を有する頭部四面体ファントムに対する放射線シミュレーション　　　　　　　　　　　　　　　
長野拓也, 松谷悠佑, 戒田篤志, 野島瞳, 古田琢哉, 佐藤薫, 吉村亮一, 三浦雅彦
日本放射線腫瘍学会第36回学術大会, 30 Nov. 2023

First-principles calculations of DNA irradiated with a proton and a carbon ion beam　　　　　　　　　　　　　　　
T. Sekikawa, Y. Matsuya, H. Beomju, M. Ishizaka, H. Kawai, Y. Ōno, T. Sato, T. Kai
The International Symposium on Quantum Science, Technology and innovation, 15 Nov. 2023

PHITSにおける物理・化学過程のシミュレーションコードの開発状況　　　　　　　　　　　　　　　
松谷悠佑, 甲斐健師, 吉井勇治, 楠本多聞, 赤松憲, 平田悠歩, 佐藤達彦
2023年度核データ+PHITS合同研究会, 15 Nov. 2023
[Invited]

ヒト由来水晶体上皮細胞での線量率効果　　　　　　　　　　　　　　　
松谷悠佑, 佐藤達彦, 浜田信行
日本保健物理学会第56回研究発表会, 10 Nov. 2023

PHITS飛跡構造シミュレーションに基づく、電子・陽子・炭素イオン誘発DNA損傷推定モデルの開発　　　　　　　　　　　　　　　
松谷悠佑, 甲斐健師, 赤松憲, 中野敏彰, 吉井勇治, 鹿園直哉, 佐藤達彦
第66回日本放射線影響学会, 08 Nov. 2023

不均質な放射線感受性を考慮した放射線治療効果推定モデルを用いた肺癌に対する体幹部定位放射線治療の局所制御率分析　　　　　　　　　　　　　　　
嵯峨涼, 松谷悠佑, 小原秀樹, 駒井史雄, 吉野浩教, 青木昌彦, 細川洋一郎
第66回日本放射線影響学会, 06 Nov. 2023

Track-structure simulation analysis for biological impacts in magnetic resonance-guided radiotherapy　　　　　　　　　　　　　　　
M. Shimoma, Y. Matsuya
The 10th meeting of educational symposium of radiation and health (ESRAH), 21 Oct. 2023

原子サイズで人体への放射線影響を予測する計算コードの開発　　　　　　　　　　　　　　　
松谷悠佑
第9回北海道大学部局横断シンポジウム「新領域創成に向けた若手連携の挑戦」, 11 Oct. 2023

A predictive model of surviving fraction under ultra-high dose-rate irradiation based on DNA damage responses　　　　　　　　　　　　　　　
Y. Shiraishi, Y. Matsuya, T. Kusumoto, H. Fukunaga
The 6th Faculty of Health Sciences (FHS) International Conference, 05 Oct. 2023

Monte Carlo simulation for dose distribution around dental metal crown　　　　　　　　　　　　　　　
K. Kudo, Y. Matsuya, T. Nagano
The 10th meeting of educational symposium of radiation and health (ESRAH), 21 Sep. 2023

Model assessment for the impact of cancer stem cells on in vitro cell survival and clinical tumor control　　　　　　　　　　　　　　　
D. Ishiyama, R. Saga, Y. Matsuya
The 10th meeting of educational symposium of radiation and health (ESRAH), 21 Sep. 2023

スポットスキャニング陽子線治療下における二次中性子線のモンテカルロシミュレーション　　　　　　　　　　　　　　　
岩田樂久, 高田健太, 松谷悠佑, 山中将史, 守屋駿佑, 松本和樹, 熊田博明, 榮武二
第126回日本医学物理学会学術集会, 15 Sep. 2023

Analysis of radiation interactions in phosphors using the PHITS track-structure mode for evaluating the response of radiation detectors　　　　　　　　　　　　　　　
Y. Hirata, T. Kai, T. Ogawa, Y. Matsuya, T. Sato
21th International Conference on Radiation Effects in Insulators (REI-21), 03 Sep. 2023

Radiolysis of liquid water occurring around ion tracks of carbon beams　　　　　　　　　　　　　　　
H. Tsuchida, T. Tezuka, T. Kai, Y. Matsuya, T. Majima, M. Saito
The 7th International Conference "Dynamics of Systems on the Nanoscale" (DySoN 2023), 24 Apr. 2023

PHITSを用いたDNA損傷計算 –マクロからミクロへの挑戦–　　　　　　　　　　　　　　　
佐藤達彦, 松谷悠佑, 甲斐健師, 小川達彦, 平田悠歩, 関川卓也
日本原子力学会 2023年秋の大会, 2023

放射線誘起正孔がもたらすDNAの分子構造と電子状態変化の第一原理計算　　　　　　　　　　　　　　　
関川卓也, ファン・ボンジュ, 石坂優人, 松谷悠佑, 川井弘之, 大野義章, 甲斐健師, 佐藤達彦
日本物理学会第78回年次大会, 2023

FLASH放射線治療効果を再現する生物効果予測モデルの開発　　　　　　　　　　　　　　　
白石祐太, 松谷悠佑, 楠本多聞, 福永久典
第60回日本放射線腫瘍学会生物部会学術大会, 2023

生体計測装置学　　　　　　　　　　　　　　　
西野学園
Sep. 2024 - Present

放射線物理学Ⅰ　　　　　　　　　　　　　　　
北海道大学
Nov. 2023 - Present

放射線化学実験　　　　　　　　　　　　　　　
北海道大学
Sep. 2023 - Present

放射線工学概論　　　　　　　　　　　　　　　
西野学園
Apr. 2023 - Present

臨床実習Ⅵ　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

臨床実習Ⅴ　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

臨床実習Ⅳ　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

臨床実習Ⅲ　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

臨床実習Ⅱ　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

臨床実習Ⅰ　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

実験研究方法特論　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

生体情報機能解析学特講　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

放射線計測学実習　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

医用画像情報学実験　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

放射線物理学Ⅱ　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

放射線物理学基礎　　　　　　　　　　　　　　　
北海道大学
Apr. 2023 - Present

生体情報機能解析学特講演習　　　　　　　　　　　　　　　
北海道大学
Nov. 2022 - Present

放射線防護学実習　　　　　　　　　　　　　　　
北海道大学
Nov. 2022 - Present

医用電子工学Ⅱ　　　　　　　　　　　　　　　
北海道大学
Nov. 2022 - Present

医用電子工学Ⅰ　　　　　　　　　　　　　　　
北海道大学
Nov. 2022 - Present

May 2021 - Present
公益社団法人日本放射線腫瘍学会　　　　　　　　　　　　　　　

Apr. 2018 - Present
JAPAN HEALTH PHYSICS SOCIETY　　　　　　　　　　　　　　　

May 2013 - Present
THE JAPANESE RADIATION RESEARCH SOCIETY　　　　　　　　　　　　　　　

May 2012 - Present
JAPAN SOCIETY OF MEDICAL PHYSICS　　　　　　　　　　　　　　　

Aug. 2012 - Apr. 2022
公益社団法人 日本放射線技術学会　　　　　　　　　　　　　　　

腫瘍内低酸素領域を加味した治療計画に資する数理モデル開発
科学研究費助成事業
Apr. 2025 - Mar. 2028
嵯峨 涼, 松谷 悠佑
日本学術振興会, 基盤研究(C), 弘前大学, 25K10953

Bottom-up analysis of radiation microscopic transport
Grants-in-Aid for Scientific Research
Apr. 2023 - Mar. 2028
小川 達彦, 安部 晋一郎, 松谷 悠佑
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Japan Atomic Energy Agency, 23K04635

水の放射線分解を模擬するシミュレーションコードの開発　　　　　　　　　　　　　　　
国家課題対応型研究開発推進事業（原子力システム研究開発事業）
Oct. 2024 - Mar. 2027
松谷悠佑, 吉井勇治
文部科学省, 国家課題対応型研究開発推進事業 原子力システム研究開発事業（新発想型（若手））, 24019683

Development of DNA damage estimation system based on spatial pattern of radiation track structure
Grants-in-Aid for Scientific Research
Apr. 2022 - Mar. 2026
松谷 悠佑, 福永 久典, 松山 成男, 赤松 憲, 甲斐 健師, 楠本 多聞
令和4年度は、DNA損傷を高速に推定可能なDNA損傷予測システムの開発に向けて、(1)化学モデルの開発、(2)イオン線照射実験の準備、(3)光子線や炭素線照射後のDNA損傷測定データの蓄積を進めた。開発や測定を進める中で得られた成果の一部は、国際的に著名なジャーナルにて3報の発表を行った。
当該年度の化学モデルの開発においては、既存の放射線輸送計算コードPHITSに実装されているイオン飛跡構造解析モードKURBUCを応用し、陽子線照射後のDNA損傷収率の計算を行うことで、高LET照射時の化学過程の重要性を確認した。同時に、当初予定していなかったが、PHITSによる計算から得られる相互作用の空間情報から、ラジカルの初期収量と時間変化を計算するコード開発に成功し、DNA損傷の発生メカニズムに関する研究を一層進めている。このコード開発に基づき、DNA損傷予測を高精度に再現する化学モデルの開発に着手した。
次に、当該年度の照射実験の準備については、東北大学高速中性子実験室の陽子ビームと中性子線の物理特性の評価を進めた。同時に、高崎量子応用研究所に設置されている低エネルギー炭素イオン源（TIARA）を使用した照射実験を行い、原子間力顕微鏡を使用することで、25 MeV/nおよび10 MeV/n炭素線（高LETイオン線）照射後に発生する様々なDNA損傷（一本鎖切断、二本鎖切断、クラスター損傷）収量の定量的測定に成功した。現在、得られた実測値に基づき、開発中の化学モデルの妥当性の確認を進めている。
以上の化学モデル開発ならびにイオン線照射実験の蓄積から、高LET放射線後の化学過程の重要性が確認され、化学モデル開発の開発ならびに検証を大いに進展させることに成功した。したがって、様々な放射線タイプにより生じるDNA損傷を高速に推定可能なDNA損傷予測システムの開発に向けて大幅に研究が進展したと思われる。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Japan Atomic Energy Agency, 22H03744

低線量生物影響を考慮したCT被曝線量指標の開発 －計算科学と生物学の分野間融合ー
科学研究費助成事業 基盤研究(C)
Apr. 2021 - Mar. 2024
佐々木 恒平, 松谷 悠佑
R3年度は低線量被ばくに対応したDNA損傷推定モデルの構築を実施した。
放射線物理過程を模擬する放射線輸送計算コード（Particle and Heavy Ion Transport code System：PHITS）を用いて、コンピュータ断層撮影（CT）検査時の生体内環境を模擬し、被ばく細胞集団のDNA損傷収率を理論計算で評価する体系構築に取り組んだ。この評価体系を構築するには2つの要素がある。（１）実際のCT検査時に装置から発生し、患者体内に到達するX線の質を正確に再現すること、（２）患者体内の細胞へ誘導されるDNA損傷数を推定し損傷の体内分布を作成すること、である。
（１）では細胞実験で用いるCT装置から発生するX線を正確に再現することが必要となる。CT装置から発生するX線は制動X線と呼ばれるものであり、そのエネルギーが広範囲に及ぶ。また、X線を発生するX線管や付加フィルタの材質や形状によって光子エネルギーは様々な分布を呈する。さらに、CT装置のコリメータなどでX線が相互作用することによっても様々なエネルギーのX線が発生し、X線管から発生するX線に混入する。よって、患者体内へ入射するX線を再現するにはそのX線のエネルギースペクトルの実測が必要となる。我々はCdTeスペクトロメータ（EMF123型）を用いてエネルギースペクトルの実測を試みたが、測定位置の制限から正確な測定が困難であった。そのため、実測した半価層とTucker式によってエネルギースペクトルを推定した。現在、PHITSに得られたエネルギースペクトルを入力したX線源モデルを作成している。
（２）以前より取り組んできた非照射細胞へ誘導されるDNA損傷を推定する細胞間シグナル伝達シミュレーションについて、本研究で扱う実験体系に合わせてパラメータを最適化した。最適化が不十分な箇所が存在するので、引き続き取り組んでいく。
日本学術振興会, 基盤研究(C), 北海道科学大学, 21K07710

不均一放射線場における放射線影響推定へ向けたモデル開発　　　　　　　　　　　　　　　
学術研究助成基金助成（若手研究）
Apr. 2019 - Mar. 2022
松谷悠佑
日本学術振興会, Principal investigator, Competitive research funding

低線量率被ばく時における放射線感受性のモデル解析　　　　　　　　　　　　　　　
科学研究費補助金
2016 - 2018
松谷悠佑
日本学術振興会, Principal investigator, Competitive research funding

北大保健同窓会 副会長　　　　　　　　　　　　　　　
Jan. 2024 - Present
Organizing member
Others

ミクロな視点で放射線を分析!　　　　　　　　　　　　　　　
03 Nov. 2023
Lecturer
Lecture
北海道大学 保健科学研究院
保健科学研究院公開講座2023「ようこそ！ヘルスサイエンスの世界へ」

DEI (Diversity, Equity & Inclusion) パネルディスカッション　　　　　　　　　　　　　　　
11 Oct. 2023
Panelist
北海道大学
第9回北大・部局横断シンポジウム

10th Educational Symposium of Radiation and Health by Young Scientist (ESRAH2023)　　　　　　　　　　　　　　　
23 Sep. 2023 - 24 Sep. 2023
Organizing member
Others

目に見えない放射線 体の中では どんな反応をおこすのか？　　　　　　　　　　　　　　　
06 Aug. 2023
Lecturer, Others
Others
北海道大学 医学部 保健学科
2023年度 オープンキャンパス

The 9th meeting of educational symposium of radiation and health (ESRAH)　　　　　　　　　　　　　　　
03 Dec. 2022 - 04 Dec. 2022
Organizing member
Others

An integrated theoretical model for estimating cell death based on the DNA damage response　　　　　　　　　　　　　　　
12 Nov. 2021 - 14 Nov. 2021
Panelist
Seminar
日本放射線影響学会第64回大会

放射線生物学へのPHITSコードの応用　　　　　　　　　　　　　　　
21 May 2021
Others
PHITSプロモーション動画公開記念オンラインセミナー

「光る精子」をもつ精子形成可視化マウスの開発に成功～革新的な生殖毒性スクリーニング技術・イノベーション創出に期待～　　　　　　　　　　　　　　　
06 Jan. 2026
北海道大学
[Internet]

放射線による水分子の化学変化から最新がん治療に迫る！～放射線で分解する水分子の挙動を視覚的に追跡する計算プログラムの開発に成功～　　　　　　　　　　　　　　　
24 Apr. 2025
Myself
国立研究開発法人日本原子力研究開発機構・北海道大学
[Internet]

放射線による発がんリスクの“出発点”に迫る！―DNA 周囲の水の分解が生命の遺伝情報を狂わせる―　　　　　　　　　　　　　　　
07 Mar. 2025
国立研究開発法人日本原子力研究開発機構
[Internet]

世界初！がん幹細胞の考慮により臨床の 放射線治療効果の予測に成功 ―基礎細胞実験と臨床研究をつなぐ予測モデルを開発―　　　　　　　　　　　　　　　
Feb. 2023
Myself
弘前大学・北海道大学・原子力機構
Yahoo! ニュース・RAB青森放送
[Media report]

世界初！あらゆる物質中の放射線の動きを原子サイズで予測 －人体や物質への放射線影響に微細世界から迫る－　　　　　　　　　　　　　　　
Dec. 2021
Myself
国立研究開発法人日本原子力研究開発機構
[Paper]