Novel GTA-PVA Fricke gels for three-dimensional dose mapping in radiotherapy

Abstract

One of the most recent and promising developments in radiotherapy dosimetry was the introduction of 3D radiation-sensitive gels. These gels present tissue equivalent composition and density, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some gels are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). These formulations suffer from spontaneous-oxidation and diffusion of ferric ions after irradiation; chelating agents such as xylenol-orange significantly reduces the latter. Other gel types consist of dispersed monomers, and rely on radiation-induced cross-linking; they form stable polymer structures, but they are typically affected by significant toxicity. In a large multicenter study, we developed and investigated new formulations of Fricke-gels based on poly-vinyl alcohol chemically cross-linked with glutaraldehyde. The formulation is safe and easy to manufacture, with a sensitivity of 0.073 Gy-1 and a diffusion coefficient of 0.17 mm2/h, it arguably offers the best all-around performance of current Fricke-infused gels. The main original outcomes of the study are described in this work, while reference is made to separate reports for specific procedures and results.