Molecular structure effects on the post irradiation diffusion in polymer gel dosimeters

Abstract

Polymer gel dosimeters have specific advantages for recording 3D radiation dose distribution in diagnostic and therapeutic medical applications. A novel system based on itaconic acid and N,N?-methylene-bisacrylamide (BIS) is hereby proposed. The radical polymerization and gel formation of these monomers have been previously studied in the synthesis of a hydrogel for non dosimetric applications. Although the 3D structure of irradiated polymeric dosimeters is usually maintained for long periods of time, it is not possible to eliminate the diffusion of the different species in the regions of dose gradients within the gel. As a consequence the dose information loose quality over time. The mobility within the gelatin structure of the already mentioned species is related to their chemical structure, and nature. In this work the effect of changes in the chemical structure of the monomers over the dosimetric sensitivity and over the post-irradiation diffusion of species was studied. One of the acrylic acid groups of the itaconic acid molecule was modified to obtain molecules with similar reactivity but different molecular sizes. Dosimetric systems with these modified species were irradiated in an x-ray tomograph at different doses up to 173 Gy, and the results were characterized by Raman spectroscopy and optical absorbance in order to study their feasibility and capabilities as dosimetric systems, and by optical-CT to analyze the post irradiation diffusion.