Analytical and Monte Carlo approaches for photon and neutron Kerma coefficient determination in gel-like polymer dosimeters

Abstract

Dosimetry in radiation therapy and nuclear applications relies on accurate determination of Kerma coefficients for photons and neutrons. This study investigates photon and neutron Kerma coefficients for 15 gel-like polymer dosimeters using analytical and Monte Carlo methods. Analytical calculations involve 36 photon energies (1 keV–20 MeV) and 39 neutron energies (2.53 × 10⁻⁸ MeV–25 MeV), while Monte Carlo simulations were executed using MCNPX-2.6 code. Results show a good agreement between methods. Photon Kerma coefficients exhibit nuanced energy dependence, with a minimum around 60 keV, followed by sharp increase due to Compton scattering and pairs production processes. Neutron Kerma coefficients display distinct responses across energy regimes, with discrepancies at lower energies attributed to significant Kerma contribution from neutron capture in nitrogen component. Relative concentrations of nitrogen and hydrogen influence tissue equivalence of gel dosimeters, achieving effectiveness for intermediate and fast neutron energies. This research enhances understanding of photon and neutron interactions within gel dosimeters, crucial for precise dosimetry in biological contexts. Future studies could explore additional dosimeter compositions and energy ranges, further advancing knowledge of radiation interactions in gel dosimeters. Overall, these findings contribute to the dosimetry field, particularly in conformal radiotherapy and 3D dose distribution verification.