Characterization of an enhanced formulation N-(3-methoxypropyl) acrylamide polymer gel dosimeter by the addition of an organic sensitizer for clinical practice

Abstract

Polymer gel dosimeters are being developed and improved to perform measurements of radiation dose distributions in 3-dimensions (3-D) for the purpose of patient specific quality assurance for cancer patients and the configuration of treatment planning systems. The effect of organic glucose sensitizer (GL) material on N-(3-methoxypropyl) acrylamide polymer gel dosimeter (NMPAGAT) was presented in this study and evaluated after irradiation using nuclear magnetic resonance (NMR) read-out technique in terms of spin–spin relaxation rate (R2) of hydrogen protons within the water molecule. The improved tissue equivalent polymers of GL-NMPAGAT were irradiated using a medical linear accelerator with photon beams with doses up to 20 Gy, energies range 6–15 MV, dose rates range 50–500 cGy/min, and irradiation temperatures range 15–25 °C. The R2 dose sensitivity of GL-NMPAGT polymer with a concentration of 25 % wt GL was improved significantly and found to be two times higher than the same gel without GL in the linear dose response of 0.07–8 Gy. The 0.07 Gy represents the minimum detectable dose in the improved dosimeters. The dosimeter was found stable within a period of up to two weeks after irradiation, which is significant. No significant dose rate, energy dependence, and irradiation temperature for the dosimeter was observed over the range studied. There is decrease in R2 values with increasing scanning temperature. The gel is water equivalent and has theoretical energy-independent response from 0.1 to 20 MeV with density of 1.023 ± 0.003 g/cm3 and Zeff of 7.53. The results of the improved dosimeter in this study (i.e., 100 %, 0.32 s−1 Gy−1, and 8 Gy linearity) are toward the upper limit compared to other polymer gel dosimeters even with sensitizer additives.