Modeling of Free‐radical Crosslinking Copolymerization of Acrylamide and N,N′‐Methylenebis(acrylamide) for Radiation Dosimetry

Abstract

AbstractOver the past decade there has been much interest in the development of three‐dimensional gel dosimeters to aid in the determination of the distribution and magnitude of absorbed dose in clinical radiation therapy. A widely used dosimeter for verification of spatial dose distribution is the polyacrylamide system, sometimes termed polyacrylamide gel (PAG). In this paper, we develop a model to describe the kinetic mechanisms in this gel dosimeter, based on the radiation‐induced copolymerization of acrylamide and bisacrylamide monomers in water and gelatin. Using the proposed model, the conversion of both monomers and total vinyl groups, the concentrations of pendant double bonds (PDB), cyclized groups and crosslinks along the polymer chains as well as temperature changes were simulated. The model predictions and experimental findings in PAG dosimeters agree for a variety of recipes and spatially uniform radiation conditions. Further experiments are required to obtain accurate kinetic parameter estimates and to verify model predictions.Comparison between the temperatures changes predicted by the model (dotted lines) and experimental data (solid lines) for PAGs irradiated to different doses.imageComparison between the temperatures changes predicted by the model (dotted lines) and experimental data (solid lines) for PAGs irradiated to different doses.