An Assessment of Monte Carlo Calculations to Determine Gamma Ray Dose from Internal Emitters

Abstract

A Monte Carlo model of [gamma]-ray diffusion is presented with a discussion of its application to dosimetry problems. Two methods of using photon history data to calculate [gamma]-ray dose are reviewed summing the energy losses from individual events, and calculating the energy fluence. Approximations in the [gamma]-ray history simulation model are analyzed and the relative importance of the various assumptions established. Studies of the spectra of scattered radiation show that results are not affected by use of a finite energy cut-off to terminate histores. The Klein-Nishina free electron approximation as a model for [gamma]-ray scattering is an adequate approximation for the purposes of [gamma]-ray dosimetry.