Mathematical Modeling of the Response of Polymer Gel Dosimeters to HDR and LDR Brachytherapy Radiation

Abstract

A model is developed to simulate the response of polyacrylamide gel (PAG) dosimeters to single spherical brachytherapy seeds. The model predicts the amount of polymer formed and crosslink density as a function of radial distance and time, using either a HDR Ir192 seed or a LDR I125 seed. Results indicate that PAG dosimeters should provide accurate dosimetry when used for HDR brachytherapy at distances larger than 4 mm from the center of the seed and that PAG dosimeters will give poor results for LDR dosimetry because of the long time available for the monomer and crosslinker to diffuse toward the seed during polymerization.