Monte Carlo simulations of CsI(Tl) scintillation crystals for use in a three-dimensional megavoltage CT scanner

Abstract

A Monte Carlo model has been devised for a study of the effects of various scintillation crystal parameters on light irradiance upon a remote lens. The purpose of these simulations is to optimise the design of the scintillation crystal array for our 3-D megavoltage CT scanner. The scanner will be attached to the gantry of a linear accelerator and will be implemented to measure and reduce errors in patient positioning during a course of cancer treatment with radiotherapy. The scintillator studied here is CsI(Tl) irradiated with 6 MV X-rays. The angular distributions of light emerging from crystals coated with specular and lambertian reflectors are compared. The effect of crystal size on the light output of crystals coated with the above reflectors is shown. The relative dependence of light output (to a remote lens) on crystal optical attenuation length and coating reflectivity is demonstrated. Comparison with some experimental data is also included. © 1994.