Biological dose estimation for charged-particle therapy using an improved PHITS code coupled with a microdosimetric kinetic model

Sato, Tatsuhiko   ; Kase, Yuki*; Watanabe, Ritsuko; Niita, Koji*; Sihver, L.*

A new method for estimating biological dose from charged-particle therapy was established, using the improved PHITS coupled with a microdosimetric kinetic model. In the method, the biological dose can be determined by multiplying the physical dose by the RBE for a surviving fraction of tumor cells, which is estimated from the saturation-corrected dose-mean lineal energy y* calculated by the improved PHITS. The accuracy of the biological dose estimated by this method was reliably verified by comparing the calculated physical doses and RBE values with the corresponding experimental data obtained by irradiating a slab phantom with the spread-out Bragg peak beams as well as several types of mono-energetic HZE particles. The simulation technique established in this study will help to optimize the treatment planning of charged-particle therapy for maximizing the therapeutic effect on tumor while minimizing unintended harmful effects on surrounding normal tissues.