Effect of inorganic salts and matrix crosslinking on the dose response of polymer gel dosimeters based on acrylamide

Abstract

The use of additives in polymer gel dosimeters to enhance their sensitivity or to improve their performance is of great importance for their application in radiomedicine. Inorganic salts have been used as additives with this purpose; however, their presence in the dosimeters induce severe modifications in their mechanical properties and consequently in their capabilities to maintain a stable dose distribution with time. Most studies in this area conclude in the need to use chemical modifications of the species responsible for the mechanical properties of the dosimeters, which in most cases is a gelatin matrix. In this study, a covalent crosslinking of the gelatin matrix of PAGAT dosimeters doped with different inorganic salts, namely MgCl2, CaCl2 and MnCl2 has been carried out. The mechanical properties, X-ray sensitivity and dose distribution stability in these materials were compared to those of PAGAT. The results indicated a compromise between the crosslinking of the gelatin structure and the sensitivity of the dosimetric material. Therefore, the proper selection of the degree of crosslinking and the inorganic salt concentration must be considered. An enhanced dosimeter was obtained by adding MgCl2 with a 1M concentration and by crosslinking the gelatin matrix with glutaraldehyde at a 0.08%w/v concentration. This material presented a 75% enhanced sensitivity relative to PAGAT and similar temporal stability and spatial stability in 2D dose distributions.