Monte Carlo法を用いた体内散乱線の解析 : Scatter-Primary Dose Ratio

抄録

A Monte Carlo computer program has been used to analyze the characteristics of scattered radiation in a phantom irradiated by Cobalt-60 gamma rays. The program simulated an irradiation by 1250 key photons with a zero area field on the center of 30×30×30 cm water phantom, and calculated the ratio of energy imparted in the ring, with depth d and with radius R, by scattered radiation to energy imparted on the beam axis with depth d by primary radiation. Based on this data and scatter-air ratio data by Gupta et al., scatter-primary dose ratios and tissue-primary dose ratios were obtained. These new concepts are applicable for any energy photons, even though in which energy it is difficult to measure air doses, keeping hold the rationality equivalent to scatter-air ratios and tissue-air ratios.