SU-E-T-111: Estimation of Characteristics for Dose Distribution in Polymer Gel by Means of Monte Carlo Simulation

Abstract

Purpose: To estimate the three dimensional dose distributions for proton, proton induced gamma rays and proton induced neutron particles, in case of exposing the proton beam to a polymer gel dosimeter and a water phantom. Methods: The polymer gel dosimeter was compositeness material of gelatin, methacrylic acid, hydroquinone, tetrakis and distilled water. The density of the gel dosimeter was 1.04g/cm3 which density was similar to water. The proton beam energies of 72 and 116 MeV were used in the simulation. Proton beam was directed to the top of a cylindrical phantom which radius was 5 cm and height was 12.2 cm for covering the proton Bragg‐peak (on X‐axis). The proton beam interacted with the nuclei of the phantom and the nuclei in excited states emitted prompt gamma rays and proton induced neutron particles during the process of de‐excitation. The proton particles, gamma prays and induced neutron were detected by the gel dosimeter and water phantom, respectively. The gap of the X‐axis was 2 mm. Results: The Bragg‐peak for proton particles in the gel dosimeter was similar to water phantom. The dose distribution for proton and prompt gamma rays in the gel dosimeter and water phantom was approximately identical in case of 72 and 116 MeV for proton beam. However, in case of proton induced neutron particles for 72 and 116 MeV proton beam, particles were not detected in the gel dosimeter, while the water phantom absorbed neutron. Conclusion: For the evaluation of proton dose distribution, the gel dosimeter was valuable tools for three dimensional measurements. This work indicates the evaluation for dose distribution of proton, induced gamma, and neutron in the gel dosimeter compared with the water phantom. Considering the Result data, the gel dosimeter which was developed in the normoxic state attentively detected the dose distribution for proton beam exposure except neutron particles.