Fricke gel dosimeters with low-diffusion and high-sensitivity based on a chemically cross-linked PVA matrix

Current radiotherapy techniques implement treatment plans based on volumetric distributions of dose with complex shapes and sharp gradients. To verify the agreement between these treatment plans and the dose that is actually delivered, a dosimetric system that is truly three dimensional, sensitive to radiation in each point and tissue equivalent is required. For this purpose, we developed a radio-chromic gel based on polyvinyl alcohol (PVA), that is chemically cross-linked with glutaraldehyde (GTA) and offers high sensitivity and stability, i.e., low diffusion, of the signal. This gel is transparent and therefore it can be read out with optical techniques. The dosimetric characteristics of the PVA-GTA gel were compared to gelatine and to literature data for so called PVA hydrogels and cryogels. The dose response of the PVA-GTA dosimeter is found to be linear between 0 and 30 Gy and its sensitivity higher than any previously reported value for PVA-based gel dosimeters. The diffusion coefficient of the PVA-GTA gel is lower than the diffusion coefficient of gel with matrixes made by natural polymers.