Characterization of Fricke-gelatin dosimeters for intraoperative Radiation Therapy dosimetry

In this work, the usability of Fricke gels in Intraoperative Radiation Therapy (IORT) dosimetry was investigated. Irradiated gel systems are characterized by means of UV/Vis spectrophotometric analysis in order to define the main dosimetric indexes of interest and to evaluate their post-irradiation stability. A measurement of Output Factors for different field sizes is also attempted to study the application of this system for routine quality control. Ad-hoc manufactured thin-layers of gel are employed to perform acquisitions of planar transverse dose profiles and to quantify the effect of Fe(III) diffusion. The Fricke gel system presents an adequate dosimetric performance, with excellent response linearity up to 30 Gy. Comparison of dosimetric response over a wide range of irradiation dose rates allows to conclude that the gel response is not influenced significantly by this parameter. Transverse dose profiles acquired with thin-layers present an agreement within 3% with reference values, even in very steep dose gradient regions. Finally, computed values for the diffusion coefficient of ferric ions are in good agreement with those reported in literature for dosimetric gels of similar composition. Overall performance of the gel system appears promising for further applications in IORT dosimetry.