Comparative evaluation of two analytical functions for the microdosimetry of ions from H to U

Parisi, A.*; Furutani, K. M.*; Sato, Tatsuhiko   ; Beltran, C. J.*

The analytical microdosimetric function (AMF) implemented in the Monte Carlo code PHITS is a unique tool that bridges the gap between macro- and microscopic scales of radiation interactions, enabling accurate microdosimetric calculations over macroscopic bodies. This study compares the older and newer AMFs in computing microdosimetric probability distributions, mean values, and the relative biological effectiveness (RBE). The newer AMF was found to offer superior performance, particularly for very heavy ions, producing results that align more closely with published in vitro clonogenic survival experiments. These findings suggest that the updated AMF provides a more reliable tool for microdosimetric calculations and RBE modeling, essential for ion radiation therapy and space radiation protection.