Standardization of gel detectors for measuring medium radiation doses in comparison with traditional reference methods

Different gel dosimetry techniques have been proposed as methods for three dimensional dose distribution measurements. Gel dosimeters were proposed for radiotherapy dosimetry at which the calibration of any dose-measuring technique is the main requirement for its proper practical application. The standardisation of the technique requires the establishment of a method for the calibration of each type of these gel materials. This study aim at determining the chemical yield for the radiochromic ''Ferrous-sulphate and Xelenol-orange Gelatine' (FXG) gel. Using the standard absorbed dose to water protocol, the radiation field is calibrated first; then a standard Fricke dosimeter is calibrated. The obtained chemical yield is G(Fe3+) = 1.63 *10-6 [mol.J-1]. Finally, FXG dosimeter was calibrated against the standard Fricke solution before calculating the system chemical yield and comparing it with Fricke system. The results show that G(FXG) 5832.18 [m2.J-1] = 17*εG(Fricke).Compared with the Fricke system, the FXG dosimeter has much higher sensitivity. In addition, the reproducibility and overall uncertainty in εG was also studied so the estimated uncertainty was founded about 6% ai confidence level 95%. Further efforts, hence, would improve the FXG dosimeter through the establishment of sensitive materials manufacturing procedures, the system calibration mechanisms and radiation effects evaluation. (author)