Examination of fundamental characteristics of a polymer gel detector in a proton beam irradiation

This paper was intended as a study of the radiological characteristics of a polymer gel detector in a clinical proton beam irradiation. The depth dose distributions in the detector were examined with regard of dose and dose rate dependences in the response. Our experimental results indicated that the dose response depended considerably on the depth from the incident position, and also the dose rate in the proton irradiation. We estimated the dose response at different depth of the incident proton beam from the depth-R2 relations with various dose, and the spread-out depth dose in a single field irradiation derived from these dose responses obtained the good agreement with a planned dose distribution. In conclusion, our method with MAGAT type polymer gel is effective in a quality assurance of fundamental reproducibility test for three dimensional radiation therapy planning system, such as monitor unit verification and standard isodose verification using a single field proton beam. However the depth dose distribution should be evaluated depending on irradiation dose rate, SOBP width, and maximum energy.