A systematic characterization of plastic scintillation dosimeters response in magnetic fields: II. Monte Carlo simulations.

Abstract

Purpose.This study aims to investigate and validate the response of plastic scintillation dosimeters (PSDs) in the presence of magnetic fields using Monte Carlo simulations, focusing on the accuracy of electron fluence, dose calculations, and the optical processes of scintillation and Cherenkov radiation.Methods.Monte Carlo simulations, using EGSnrc and TOPAS, of the PSD response under magnetic fields were performed. First, electron fluence simulations were conducted with three different physics listsg4em-penelope,g4em-standard_opt3andg4em-standard_opt4, with the goal of benchmarking their performance in magnetic fields. Secondly, a Fano test for dose calculations was performed using only theg4em-penelopephysics list. Thirdly, the Cherenkov process under magnetic fields was validated against theoretical predictions. Finally, a PSD probe was modeled and simulated, with results compared against measurements.Results.Theg4em-penelopephysics list demonstrated a most balanced performance, showing the closest agreement with EGSnrc simulations and lower variability in magnetic fields thang4em-standard_opt4. Fano test results showed an accuracy of at least 0.36% for dose calculations. Simulations of Cherenkov radiation in ideal conditions were in agreement with theoretical predictions at both 0 T and 1.5 T. Monte Carlo simulations successfully reproduced experimental trends for Cherenkov radiation under magnetic fields. However, discrepancies were found, with deviations of up to 7.7% when electrons were deflected towards the tip and up to 21.0% in the opposite direction, likely due to modeling limitations. A key result is that Monte Carlo simulations of the scintillation process in magnetic fields failed to reproduce experimental observations. While experimental results showed a significant effect of magnetic fields on scintillation yield, the simulations did not reflect this behavior.Conclusion.This study establishes that TOPAS, specifically using theg4em-penelopephysics list, is a reliable tool for simulating dose, electron fluence, and Cherenkov radiation in the presence of magnetic fields. However, significant discrepancies were observed in the scintillation processes, where Monte Carlo simulations failed to reproduce the effect of magnetic fields seen in experimental measurements. These findings point out the need for further refinement of simulation models, particularly in accurately representing scintillation under magnetic fields.