Temperature behavior of radiochromic poly(vinyl-alcohol)-glutaraldehyde Fricke gel dosimeters in practice

The use of synthetic gel matrices prepared with poly(vinyl-alcohol) (PVA) cross-linked by glutaraldehyde (GTA) contributed to enhance the interest toward radiochromic Fricke gel (FG) dosimeters. As it occurs in several chemical dosimeters, the response of PVA-GTA Fricke gels could be affected by temperature. Aim of this work is to study the dependence of the dosimetric properties of PVA-GTA Fricke gel dosimeters both on the irradiation temperature and on temperature changes possibly occurring between the irradiation and readout phases. Such effects were investigated by means of magnetic resonance imaging and optical absorbance measurements. The results did not reveal any significant dependence of the sensitivity of the dosimeters on the irradiation temperature in the investigated interval 20-35 C. By contrast, auto-oxidation phenomena confirmed to be a critical aspect for FG dosimeters, also in case of use of PVA matrix. The extent such phenomena, that might impair the accuracy of dose estimations, proved to critically depend on the temperature at which FG dosimeters are subjected before and after irradiation, as well as on the duration of possible thermal-stress.