Use of salicylic acid derivatives as $Fe^{3+}$ chelating agents in Fricke gel dosimetry.

Fricke gel (FG) dosimeters are based on chemical dosimeters in which radiation induced chemical reactions occur. Despite extensive research over the last three decades, FG dosimeters have yet to achieve widespread clinical acceptance, mainly because of some practical concerns. In particular, the reduction of spatial instability of dosimetric information is a major challenge. In this work, the well-known poly(vinyl-alcohol) (PVA)-based hydrogel was enriched by different salicylic acid derivatives as chelating agents for $Fe^{3+}$. The scope is providing the covalent functionalization of PVA with few steps and with high yield, with the aim to reduce the ions diffusion. Among the chelating agents tested, only 4-aminosalicylic acid (4-ASA) appeared suitable for both dosimetric application and covalent functionalization of the polymeric matrix. The dosimetric characterization was performed by using 4-ASA in solution and linked to the PVA-matrix and irradiating the gel samples with x-rays generated by a LINAC. A successful development of such dosimetric materials would also lead to implementation of their use in a clinical practice.