Ponente
Descripción
Radiochromic films (RCFs) have been widely used for dosimetry in photon, electron, and proton radiation therapy due to their tissue-equivalent response and high spatial resolution. However, when used with proton beams, especially at energies below 20 MeV, RCFs exhibit dose underestimation, a phenomenon known as LET quenching. This underestimation necessitates the application of a Relative Efficiency (RE) correction factor, which accounts for the reduced dose response of the film as the Linear Energy Transfer (LET) increases.
In this study, we propose an optimized model for correcting the RE of EBT3 radiochromic films irradiated with low-energy protons. Previous models, such as the Sánchez-Parcerisa 2021 model, have attempted to describe RE as a linear function of LET, with limited success in high-LET regions. To address this, we conducted a series of irradiations at the Centro de Microanálisis de Materiales (CMAM) using proton beams with an energy of 10 MeV and measured dose distributions in stacks of unlaminated EBT3 films. Additionally, materials such as PDMS, Flexdym™, and glass were placed in the beam path to evaluate the effects on the dose and LET distributions. The experimental dose values were compared to Monte Carlo simulations conducted using the TOPAS toolkit, where scoring for dose and LET in the active layer of the films was performed.
Our results demonstrate a significant discrepancy between the measured and simulated doses in regions with high LET. The current Sánchez-Parcerisa model was unable to fully account for this loss in RE, particularly for LET values above 20 KeV/um. Through the application of a bootstrapping technique, we developed a new model to fit experimental data to an improved RE(LET) function. This model, validated through uncertainty analysis, shows a substantial improvement in predicting dose in high-LET regions compared to the previous model.
Preliminary findings suggest that the optimized model provides more accurate dose predictions for proton energies below 10 MeV, reducing the uncertainties observed in the experimental data. This correction will enable a more precise dose estimation in proton therapy, especially in applications where low-energy protons are used, improving treatment outcomes.
