Polymer gel dosimeters with reduced toxicity and enhanced performance.

摘要

Polymer gel dosimetry is a promising technique used by medical physicists to verify spatial dose distributions delivered by cancer radiotherapy equipment. The polymer gels consist of an acrylic monomer and crosslinker (often acrylamide and N,N'-methylene-bisacrylamide) dissolved in an aqueous gelatin matrix, and copolymerization reactions are induced by the radiation. The amount of polymer produced in different parts of the dosimeter is dependent on the locally absorbed radiation dose. Three-dimensional dose distributions can be determined using Magnetic Resonance Imaging (MRI) and optical techniques.;The severe toxicity of the acrylamide monomer makes current polyacrylamide gel (PAG) dosimeters hazardous and inconvenient to use, and have so far prevented a wide-spread clinical acceptance. In this thesis, promising results were obtained with new polymer gel dosimeter recipes developed using less toxic monomers in place of acrylamide. H-NMR measurements indicated an MRI response of N-isopropylacrylamide gel dosimeters comparable to PAG, while diacetone acrylamide and N-vinylformamide dosimeters had significantly lower dose-sensitivities. The gradual increase in opacity of the gels with dose allowed for analysis by optical techniques as well. In the future, the new gel recipes should be optimized, and spatial resolutions of the dosimeters should be investigated using non-uniform radiation. (Abstract shortened by UMI.).