Validation of the TOPAS Monte Carlo toolkit for LDR brachytherapy simulations. (March 2023) - Poher, Audran
Abstract: Purpose: This work has the purpose of validating the Monte Carlo toolkit TOol for PArticle Simulation (TOPAS) for low-dose-rate (LDR) brachytherapy uses. Methods and Materials: Simulations of 12 LDR sources and 2 COMS eye plaques (10 mm and 20 mm in diameter) and comparisons with published reference data from the Carleton Laboratory for Radiotherapy Physics (CLRP), the TG-43 consensus data and the TG-129 consensus data were performed. Sources from the IROC Houston Source Registry were modeled. The OncoSeed 6711 and the SelectSeed 130.002 were also modeled for historical reasons. For each source, the dose rate constant, the radial dose function and the anisotropy functions at 0.5, 1 and 5 cm were extracted. For the eye plaques (loaded with 125 I sources), dose distribution maps, dose profiles along the central axis and transverse axis were calculated. Results: Dose rate constants for 11 of the 12 sources are within 4% of the consensus data and within 2% of the CLRP data. The radial dose functions and anisotropy functions are mostly within 2% of the CLRP data. In average, 92% of all voxels are within 1% of the CLRP data for the eye plaques dose distributions. The dose profiles are within 0.5% (central axis) and 1% (transverse axis) of the reference data. Conclusion: The TOPAS MC toolkit was validated for LDR brachytherapy applications. Single-seed and multi-seed results agree with the published reference data. TOPAS has several benefits such as a simplified approach to MC simulations and an accessible brachytherapy package including comprehensive learning resources. Highlights: TOPAS is user-friendly by using parameter files which do not require advanced coding knowledge. TOPAS is now a state-of-the-art Monte Carlo simulation toolkit for LDR brachytherapy. This work provides TOPAS users with a pre-made LDR brachytherapy geometries package. TOPAS provides a tutorial to help users create brachytherapy Monte Carlo simulations.