Abstract

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Title:: An accurate method for calculating biological effective doses of therapeutic heavy ions based on microdosimetric Monte Carlo simulation

Author(s):: DAI Tianyuan1; 2; 3; 4; LI Qiang1; 2; 3; 4; CHEN Weiqiang1; 2; 3; 4; LIU Xinguo1; 2; 3; 4; DAI Zhongying1; 2; 3; 4; HE Pengbo1; 2; 3; 4; MA Yuanyuan1; 2; 3; 4; SHEN Guosheng1; 2; 3; 4; ZHANG Hui1; 2; 3; 4; 1. Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China; 2. Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China; 3. Gansu Provincial Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Lanzhou 730000, China; 4. School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China

Keywords:: ; Keywords: microdosimetry; biological effective dose; microdosimetric-kinetic model; heavy ion therapy; Monte Carlo simulation

Abstract:: Abstract: Objective To calculate the biological effective dose of therapeutic heavy ions accurately by introducing ideal tissue equivalent proportional counter (Ideal TEPC) into Monte Carlo (MC) simulations and combining it with microdosimetric-kinetic model (MKM). Methods The biological effective dose of the carbon ion beam with the energy of 330 MeV/u and 6 cm spread-out Bragg peak (SOBP) was calculated using Ideal TEPC and MC simulation. Results The optimized parameters of MKM were as follow: [α0=0.12 Gy-1], rd=0.39 μm, Rn=3.7 μm. The calculation for the biological effective dose of the carbon ion beam with the energy of 330 MeV/u and 6 cm SOBP showed that the biological effective dose calculated by MKM were in good agreement with that in carbon ion treatment planning system (ciPlan), and that the deviations between them became greater with the increasing of penetration depth. The deviations were 0.3%, 1.7%, 2.7%, 4.9% and 10.3% at plateau region, SOBP front-end, SOBP midpoint, SOBP rear-end and tail region, respectively. Conclusion Ideal TEPC combined with MC simulation, with good portability, can be used to calculate the biological effective dose of therapeutic heavy ions accurately while eliminating the distortion of radiation field caused by TEPC wall, the effect of [δ] electrons produced by structural materials on lineal energy spectrum, and the location errors in the experiments.