Determination of WER and WET equivalence estimators for proton beams in the therapeutic energy range using MCNP6.1 and TOPAS codes

Abstract

To use the dosimetric advantages that proton therapy provides, the exact knowledge of the range and its associated parameters of the beam is essential. Since the human body is composed of several tissues whose composition and density differ from water it is important to relate the range in water to the range in those tissues. Those range associated parameters are the Water Equivalent Ratio (WER) and Water Equivalent Thickness (WET). This work presents the Range, WER and WET values obtained from the simulations using the Monte Carlo codes MCNP6.1 and TOPAS for several tissue-equivalent materials, which are materials that reproduce the radiation behavior of the human tissues in a phantom. Simulations have been done in the therapeutic proton energy range from 70 to 225 MeV. Therefore, the main objective of this work is to provide and contribute to the improvement of dose calculation in proton therapy, more specifically in the calculation of WER and WET in tissue equivalent medium. The results showed good agreement between codes, presenting only small differences less than 1.9% in the cortical bone, but they did not affect the dose calculation in the therapeutic range used in this study.