The role of Monte Carlo simulation of electron transport in radiation dosimetry

Abstract

A brief overview is given of the role in radiation dosimetry of electron transport simulations using the Monte Carlo technique. Two areas are discussed in some detail. The first is the calculation of stopping-power ratios for use in ion chamber dosimetry. The uncertainty in stopping-power ratios is discussed with attention being drawn to the fact that the relative uncertainty in restricted collision stopping powers is greater than that in unrestricted stopping powers if the major source of uncertainty is the density effect correction. Using ICRU Report 37 stopping powers and electron spectra calculated in a small cylinder of graphite, the value of the Spencer—Attix graphite to air stopping-power ratio in a 60Co beam is found to be 1.0021 for an assumed graphite density of 1.70 g/cm 3 and 0.23% less for an assumed density of 2.26 g/cm 3. The second area discussed is the feasibility of using Monte Carlo techniques to calculate dose patterns in a patient undergoing electron beam radiotherapy.