CONICET | Buscador de Institutos y Recursos Humanos

Dosimetric protocols are based on determinations of absorbed dose in reference conditions defining specific measurement depth (zmax) in a homogeneous water phantom. Quality assurance should be performed in water-equivalent media, i.e. materials presenting the same absorption and scattering properties as water for the involved radiation. However, practical clinical situations involve inhomogeneities within the phantom or directly due to the employed dosimeter itself, thus requiring suitable conversions to link the readout with in-water absorbed dose, as required by protocols. This process incorporates intrinsic uncertainties in the corresponding calibration factors. Therefore, dosimetry systems directly based on in-water measurements are the only reliable option to overcome these drawbacks. Gel dosimeters (Fricke and polymers) appear as the most suitable option to design dosimeters capable of performing direct measurements of absorbed dose in aqueous media acting as sensitive material in the detection system. Although water-equivalence for some gel dosimeters at radiotherapy energy ranges was already investigated, there is a lack of studies reporting physical and radiological properties of different gel dosimeter types at low energies for radiology imaging. This study reports on theory and Monte Carlo approach aimed at characterizing physical and radiological parameters affecting water-equivalence properties of gel dosimeters at low (130 keV) energies typical for imaging radiology. Moreover, theoretical predictions for different gel dosimeter formulations (Fricke, PAGAT, NIPAM, and ITABIS) were successfully benchmarked by direct experimental measurements of radiological properties performed by the high resolution micro-Computed Tomography facility at the X-ray imaging line at LIIFAMIRX, confirming overall water-equivalence for all gel dosimeters presenting variations with respect to water in the low energy radiology range less than 3% in average.