Modelling small block aperture in an in-house developed GPU-accelerated Monte Carlo-based dose engine for pencil beam scanning proton therapy

• Published in: arXiv.org
• Main Authors: Feng, Hongying, Holmes, Jason M, Vora, Sujay A, Stoker, Joshua B, Bues, Martin, Wong, William W, Sio, Terence S, Foote, Robert L, Patel, Samir H, Shen, Jiajian, Liu, Wei
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 04.07.2023
• Subjects: Apertures; Graphics processing units; Mathematical models; Optimization; Pencil beams; Proton beams; Radiation therapy; Robustness

Purpose: To enhance an in-house graphic-processing-unit (GPU) accelerated virtual particle (VP)-based Monte Carlo (MC) proton dose engine (VPMC) to model aperture blocks in both dose calculation and optimization for pencil beam scanning proton therapy (PBSPT)-based stereotactic radiosurgery (SRS). Methods and Materials: A block aperture module was integrated into VPMC. VPMC was validated by an opensource code, MCsquare, in eight water phantom simulations with 3cm thick brass apertures: four were with aperture openings of 1, 2, 3, and 4cm without a range shifter, while the other four were with same aperture opening configurations with a range shifter of 45mm water equivalent thickness. VPMC was benchmarked with MCsquare and RayStation MC for 10 patients with small targets (average volume 8.4 cc). Finally, 3 patients were selected for robust optimization with aperture blocks using VPMC. Results: In the water phantoms, 3D gamma passing rate (2%/2mm/10%) between VPMC and MCsquare were 99.71\(\pm\)0.23%. In the patient geometries, 3D gamma passing rates (3%/2mm/10%) between VPMC/MCsquare and RayStation MC were 97.79\(\pm\)2.21%/97.78\(\pm\)1.97%, respectively. The calculation time was greatly decreased from 112.45\(\pm\)114.08 seconds (MCsquare) to 8.20\(\pm\)6.42 seconds (VPMC), both having statistical uncertainties of about 0.5%. The robustly optimized plans met all the dose-volume-constraints (DVCs) for the targets and OARs per our institutional protocols. The mean calculation time for 13 influence matrices in robust optimization by VPMC was 41.6 seconds. Conclusion: VPMC has been successfully enhanced to model aperture blocks in dose calculation and optimization for the PBSPT-based SRS.