Factors influencing the thermal stability of HEMA polymer gel dosimeters for clinical radiotherapy

Thermal stability is an essential feature required for practical applicability of gel dosimeters in radiation therapy planning system (TPS). This study pioneers a comprehensive experimental study of various factors that influence thermal stability of Polymer Gel Dosimeters (PGDs) by investigating the impact of gelatin source and its weight fraction (WF), type and WF of antioxidant, presence of maltose as a disaccharide additive, and the storage time post manufacturing, on the thermal properties of 2-hydroxymethyl methacrylate (HEMA) PGD. Results show that in terms of fast gelation and gel strength, gelatin from bovine skin outperforms gelatin from cold water fish, withstanding temperature up to 11 ?C aboves its Tm, and tetrakis(hydroxymethyl)phosphonium chloride (THPC) outperforms ascorbic acid (AscA), and sample with maltose additive outperforms sample without maltose. The melting rate (Rm) increases with the temperature difference above Tm, and storage time post manufacturing, improves the thermal stability. These findings contribute to the identification of the causes of gel instability and propose the possible solutions that could lead to more accurate assessments and maintenance of dose distribution in three-dimension (3D), and to extend the shelf life of PGDs.