Chemical-physical and dosimetric characterization of PVA mixtures for Fricke gel dosimetry.

Fricke gel (FG) dosimeter is a promising technique because it is a 3D dosimeter suitable for relative dose measurements and it is particularly useful for dose verification in complex clinical situation. It consists of a radiation sensitive chemical and a hydrogel matrix that acts as mobility reducing agent. This one could be based on natural polymers ($e.g.$, gelatine or agarose) or synthetic polymers. Among them, Poly(vinyl-alcohol) (PVA) have shown the best results in terms of dosimetric properties. Nevertheless, the molecular weights and the degree of hydrolyzation of PVA influence the sensitivity and diffusion coefficient of FG. The aim of this work is, indeed, the in deep investigation of how the chemical characteristics of PVA influence the hydrogel matrix in terms of both chemical-physical and dosimetric response. In particular different mixtures of PVA at various w/w percentages are fully characterized according to dosimetric and chemical-physical assessment ($e.g.$, viscosity, gel fraction, swelling test, young modulus and compressive strength) and they are compared with the currently used PVA to find the best hydrogel formulation for FG dosimetry applications.