RapidBrachyMCTPS 3.0: recent updates and validation of RapidBrachyMCTPS, a Monte Carlo-based brachytherapy treatment...

Objective.RapidBrachyMCTPS is a Monte Carlo (MC)-based treatment planning system for advanced brachytherapy dosimetry applications. In this work, we present the latest updates in RapidBrachyMCTPS v3.0 and benchmark its dose calculations against published guidelines.Approach.RapidBrachyMCTPS v3.0 introduces a major redevelopment of RapidBrachyMC, its underlying MC dose calculation engine. Simulation times were reduced, greater user control over simulation geometry was enabled, and material definitions were greatly simplified and standardized. Test cases developed by the working group on model-based dose calculation algorithms in brachytherapy (WGDCAB) were used to benchmark dose calculation accuracy and quantify improvements in simulation efficiency relative to v2.0.Main results.For four water phantom-based WGDCAB test cases, mean and root-mean-square dose differences between reference data and RapidBrachyMCTPS v3.0-calculated dose distributions were within the estimated total uncertainty budget of 0.4%. Target structure dose-volume histogram metrics for site-specific WGDCAB test cases, one for gynecological tandem and ring brachytherapy and the other for interstitial breast brachytherapy, showed generally good agreement, within 0.01 Gy or 0.10 percentage points, with the same metrics calculated from reference dose distributions. Observed simulation run times for test cases were on average between1.63±0.02and1.66±0.03times faster than v2.0 without an applicator model and between1.45±0.01and1.91±0.02times faster with an applicator model, depending on the applicator modeling scheme used.Significance.RapidBrachyMCTPS v3.0 was well-validated to deliver fast, accurate MC dose calculations alongside robust treatment planning capabilities. It remains freely available to the research community.