IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
MOLECULAR STRUCTURE EFFECTS ON THE POST IRRADIATION DIFFUSION IN POLYMER GEL DOSIMETERS
Autor/es:
MATTEA F; ROMERO M; VEDELAGO J; QUIROGA A; VALENTE M; STRUMIA M
Lugar:
Cusco
Reunión:
Simposio; XIV INTERNATIONAL SYMPOSIUM ON SOLID STATE DOSIMETRY; 2014
Resumen:
Polymer gel dosimeters have specific advantages for recording 3D radiation dose distribution representing a key factor for most of the therapeutic and diagnostic radiation techniques. Radiation-induced polymerization and crosslinking reactions that take place in the dosimeter have been studied for different monomers like acrylamide and N,N?-methylene-bisacrylamide (BIS) and most recently for less toxic monomers like N-isopropylacrylamide and BIS. In this work a novel system based on itaconic acid and BIS is proposed, the radical polymerization or gel formation of these monomers has been already studied for the formation of an hydrogel for non dosimetric applications and their reactivity are comparable with the already mentioned systems. Although the 3D structure is maintained after the dosimeter has been irradiated, it is not possible to eliminate the diffusion of the reacted and monomer species in regions of dose gradients within the gel after irradiation. As a consequence the dose information of the dosimeters 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 is studied. One of the acrylic acid groups of the itaconic acid molecule is modified to obtain molecules with similar reactivity but different molecular sizes in the final form presented in Figure 1. Fig. 1.- Modified itaconic acid. Examples of R are ethyl, propyl and terbutyl groups. Dosimetric systems with these modified species, BIS, an antioxidant to avoid oxygen polymerization inhibition, water and gelatin are irradiated in an x-rays tomograph at different doses, and the resulting dosimeters are characterized by Raman spectroscopy and optical absorbance to study their feasibility and capabilities as dosimetric systems, and by optical-CT to analyze the diffusion degree after being irradiated.