Development of a Monte Carlo dosimetry system for retrospective study of heavay-ion therapy

Furuta, Takuya   ; Koba, Yusuke*; Chang, W.*; Hashimoto, Shintaro  ; Yonai, Shunsuke*; Matsumoto, Shinnosuke*; Sato, Tatsuhiko   

Heavy-ion (carbon-ion) therapy has advantages over conventional radiotherapy such as superior dose concentration and better relative biological effectiveness while the secondary particles produced by nuclear reactions between incident carbon ions and matters induce complexity for risk assessment of secondary cancer. For this assessment, precise transport calculation of secondary particles are required so the Monte Carlo transport calculation is desired. We therefore construct a dosimetry system including PHITS as the engine. In this system, the PHITS input is automatically created from the DICOM data sets recorded in the treatment planning. The transport calculation is simulated by PHITS and dose distribution around the tumor but also out-of-filed is computed. This system will be used as retrospective study in National Institute of Radiological Sciences.