SU-E-T-530: Comparison of Analytical and Monte Carlo Calculations for Heterogeneity Corrections in LDR Prostate Brachytherapy

Abstract

Purpose: It is well‐known that tissue heterogeneities and calcifications have significant influence on low energy brachytherapy. The aim of this work is to study the application of a simplified analytic algorithm that could be compatible with commercial Treatment Planning System (TPS) based on TG‐43. The algorithm, based on the classic equivalent path length method, has been compared with Monte Carlo (MC) computations using Penelope2009. Methods: The analytical model scales the distance from the seed to the calculation point according to the electronic density of the medium relative to water. Then, the dose is calculated from TG‐43 consensus data (stored on a TPS) by scaling the radial dose function according to the equivalent path length, keeping the anisotropy function unaltered. A voxelized phantom obtained from clinical cases has been used. This benchmark was selected because the patient presented a significant proportion of calcifications inside the prostate. After this, a comparison between MC and the algorithm was performed. Results: The results given by the algorithm show a remarkable agreement with the complete Monte Carlo simulations taking into account the calcifications (real case). Several other realistic geometries and compositions of the calcification have been checked successfully. Conclusion: The presented analytical dose calculation is applicable for any type of heterogeneity. Its high calculation speed makes it feasible for use in clinical real time‐treatment planning and thus for improving treatment quality.