Application of Polymer Gel dosimetry in Dose Verification of IMRT

Dosimetry is an integral part of radiotherapy and dose verification is one of the important stages in modern radiotherapy. Nowadays gel dosimeters are the only dosimeters that can record dose distribution in three dimensions only with a single measurement. The purpose of this study was to evaluate the capability of polymer gel dosimetry in dose verification of compensator-based IMRT. A cerrobend slab with 4 cm thickness was manufactured and percentage depth dose curves for 18 MV photon beam and 10×10 cm2 field size were obtained by ionization chamber and polymer gel dosimeter. Then, an anthropomorphic pelvic phantom with gel inserts was constructed and irradiated with compensator-based IMRT technique. A comparison of the result of dose measurements with ion chamber and gel dosimeter showed that in spite of changing mean beam quality, compensators have no effect on response of gel dosimeter. Besides, according to distance to agreement (DTA) analysis there was good agreement between calculated and gel measured dose distributions. The methodology presented in this work proved the feasibility of polymer gel dosimeter as an ideal tool for pretreatment IMRT QA and also the constructed phantom can be used efficiently in other radiotherapy techniques. Future works will be focused on the development of lung equivalent polymer gel dosimeter.