A set of studies was performed to demonstrate the functionality of the new gPMC code, as well as to comprehensively validate its accuracy. Specifically, total dose, dose of primary protons, secondary protons and other heavier ions, fluence of primary protons and secondary protons, as well as LETd were compared to the results computed by TOPAS (Perl et al 2012 (link)). For dose comparison, pencil beam with zero width was simulated and the result was integrated laterally to obtain the dose distribution of a broad beam with a size of 5×5 cm2. The choice of a pencil beam was because dose and fluence distributions on the central beam axis from this infinitesimal beam are very sensitive to discrepancies in angular deflection and angular distribution of protons. In contrast, the broad beam is more realistic and was hence used to evaluate the accuracy in a more clinically relevant setup. For LETd comparison, 2×2 cm2 broad beams were studied. The phantom we used was a pure water phantom of 10.1×10.1×30 cm3 in dimension with a voxel size of 0.1×0.1×0.1 cm3. 100 MeV and 200 MeV mono-energetic beams normally impinged on the phantom surface.
The second scenario studied was a prostate cancer patient. gPMC v1.0 was reported to have a systematic overestimation in dose at the entrance region and underestimation at the target for prostate cases due to approximations in nuclear interaction models (Giantsoudi et al., 2015 (link)). To demonstrate the improvements made in this new version, a prostate cancer patient with two laterally opposite beams was used. Dose in this patient was computed with gPMC v1.0, gPMC v2.0 and TOPAS.
The efficiency and cross-platform portability of gPMC v2.0 were tested with several different devices including an NVidia GeForce GTX TITAN GPU card, an AMD Radeon R9 290x GPU card, an Intel i7-3770 CPU processor and an Intel Xeon E5-2640 CPU processor. We also conducted tests with different numbers of dose counters to investigate its impact on the memory conflict issue.
The second scenario studied was a prostate cancer patient. gPMC v1.0 was reported to have a systematic overestimation in dose at the entrance region and underestimation at the target for prostate cases due to approximations in nuclear interaction models (Giantsoudi et al., 2015 (link)). To demonstrate the improvements made in this new version, a prostate cancer patient with two laterally opposite beams was used. Dose in this patient was computed with gPMC v1.0, gPMC v2.0 and TOPAS.
The efficiency and cross-platform portability of gPMC v2.0 were tested with several different devices including an NVidia GeForce GTX TITAN GPU card, an AMD Radeon R9 290x GPU card, an Intel i7-3770 CPU processor and an Intel Xeon E5-2640 CPU processor. We also conducted tests with different numbers of dose counters to investigate its impact on the memory conflict issue.
