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Matsuya, Yusuke; Kai, Takeshi; Sato, Tatsuhiko; Liamsuwan, T.*; Sasaki, Kohei*; Nikjoo, H.*
Physics in Medicine & Biology, 66(6), p.06NT02_1 - 06NT02_11, 2021/03
Times Cited Count：17 Percentile：90.49(Engineering, Biomedical)A general-purpose Monte Carlo radiation transport simulation code, Particle and Heavy Ion Transport code System (PHITS), has the ability to handle diverse particle types over a wide range of energy. In PHITS version 3.20, ion track structure mode has been developed based on the algorithms in the KURBUC code, which enables to simulate the atomic interactions by primary ion and secondary particles (named as PHITS-KURBUC mode). In this study, we compared the range, radial dose distributions, and microdosimetric distributions calculated using the PHITS-KURBUC mode to 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. This PHITS-KURBUC mode is expected to pave the way for next-generation radiation researches, such as radiation physics, radiological protection, medical physics, and radiation biology.
Watanabe, Ritsuko; Rahmanian, S.*; Nikjoo, H.*
Radiation Research, 183(5), p.525 - 540, 2015/05
Times Cited Count：69 Percentile：94.84(Biology)To calculate the spectrum of initial base damage induced by selected electrons and ions, Monte Carlo track structure method was used to simulate the radiation induced DNA damage in a cell mimetic condition based on a single track action. We present relative yield of strand breaks and base damage for selected monoenergetic electrons 100 eV - 100 keV, photons C
, Al and Ti; and some selected ions (3.2 MeV/u proton; 0.74 and 2.4 MeV/u 
He; 29 MeV/u 
N, and 950 MeV/u 
Fe). Data are presented for simple and complex types of DNA damage. The ratios of yields of base damage to SSBs were estimated to be about 2-4 independent on the LETs examined. The contribution of base damage to the complexity of damage site was shown to be significant. The data can be used for testing mechanistic models of DNA repair kinetics and in particular the base excision repair.
Nikjoo, H.*; Emifietzoglou, D.*; Watanabe, Ritsuko; Uehara, Shuzo*
Radiation Physics and Chemistry, 77(10-12), p.1270 - 1279, 2008/10
Times Cited Count：54 Percentile：95.02(Chemistry, Physical)Microdosimetry and track structure have been applied to scrutinize and understand aspects of radiation damage in biological molecules from a theoretical approach. To this end track structure has provided a basis for understanding the mechanism(s) that shape dose-effect relationships. There is a wealth of information and data accumulated from radiation biology that need to be placed in the framework of a general descriptive theory. While there are many classical radiobiology questions remain unanswered new ideas and challenging question are emerging. Among many, simulation of radiation track at molecular level is an emerging tool in radiobiology and theoretical radiotherapy. In this paper we present recent progress in development of low energy electron tracks in condensed media and high energy proton tracks and discuss progress in characterizing DNA damage in terms of types and complexity.
Watanabe, Ritsuko; Nikjoo, H.*
International Journal of Radiation Biology, 78(11), p.953 - 966, 2002/11
Times Cited Count：39 Percentile：90.08(Biology)Incorporation of halogenated pyrimidines, iodo- and bromo-deoxyuridines (HP), into DNA is known to sensitize cells to radiation. The aim of this study is to estimate the enhancement of DNA strand break induced by low LET radiation in the presence of HP and examine source, complexity and clustering properties of damage that could provide correlation between DNA damage and lethality. Monte Carlo track structure methods were used to model the induction of strand breakage by X-ray photons. As a result, the increase of strand breaks due to Br/IdU incorporation could be explained by the mechanism of uracilyl radical production originated from e-aq and direct hits on bases. The significant contribution of electron migration along DNA within limited distance is shown. It is also shown that the incorporation of Br/IdU causes a spectral shift towards greater complexity of clustered DNA damage. Further, it has been supported that DSB is responsible for radiation-induced cell killing.
Watanabe, Ritsuko; Nikjoo, H.*
no journal, ,
no abstracts in English
Kai, Takeshi; Sato, Tatsuhiko; Liamsuwan, T.*; Nikjoo, H.*
no journal, ,
A general purpose particle transport simulation code, PHITS is expected to apply dose evaluation in macroscopic systems as well as radiation interaction investigation in nanoscale for study of interaction between radiations and materials. To clear the problem, we implemented track structure calculation codes into the PHITS. The codes make microscopic behavior as well as energy depositions (ionization and excitation) of the electrons, protons and carbon ions possible. The PHITS could evaluate radiation dose of cellar size. As this implementation, DNA damage predictions, which need radiation interaction in the molecular levels, will be expected using this track-structure simulation mode.
