Implementation of simplified stochastic microdosimetric kinetic models into PHITS for application to radiation treatment planning. (3rd October 2021)

• Record Type: Journal Article
• Authors: Sato, Tatsuhiko; Hashimoto, Shintaro; Inaniwa, Taku; Takada, Kenta; Kumada, Hiroaki
• Is Part Of: International journal of radiation biology. Volume 97:Number 10(2021)
• Page Start: 1450
• Page End: 1460
• Publication Date: 2021-10-03
• Subjects: Microdosimetry -- treatment planning -- Monte Carlo -- RBE -- PHITS; Radiation -- Physiological effect -- Periodicals; Radiobiology -- Periodicals; 571.45
• DOI: 10.1080/09553002.2021.1956003
• Languages: English
• ISSNs: 0955-3002

Abstract

Abstract: Purpose: The stochastic microdosimetric kinetic (SMK) model is one of the most sophisticated and precise models used in the estimation of the relative biological effectiveness of carbon-ion radiotherapy (CRT) and boron neutron capture therapy (BNCT). However, because of its complicated and time-consuming calculation procedures, it is nearly impractical to directly incorporate this model into a radiation treatment-planning system. Materials and methods: Through the introduction of Taylor expansion (TE) or fast Fourier transform (FFT), we developed two simplified SMK models and implemented them into the Particle and Heavy Ion Transport code System (PHITS). To verify the implementation, we calculated the photon isoeffective doses in a cylindrical phantom placed in the radiation fields of passive CRT and accelerator-based BNCT. Results and discussion: Our calculation suggested that both TE-based and FFT-based SMK models can reproduce the data obtained from the original SMK model very well for absorbed doses approximately below 5 Gy, whereas the TE-based SMK model overestimates the original data at higher doses. In terms of computational efficiency, the TE-based SMK model is much faster than the FFT-based SMK model. Conclusion: This study enables the instantaneous calculation of the photo isoeffective dose for CRT and BNCT, considering their cellular-scale dose heterogeneities. Treatment-planning systems that use the improved PHITS as a dose-calculation engine are under development.