Proton treatment-plan dose verification with a DPM-based Monte Carlo engine
Abstract
IntroductionIndependent proton dose verification requires a calculation pathway that is accurate enough to identify clinically relevant discrepancies while remaining practical to commission and operate. We use a pre-release version of the commercial RadMonteCarlo, a multithreaded CPU-based proton Monte Carlo engine built on a dose planning method (DPM) framework for independent treatment-plan recalculation. In this study, we evaluate the sensitivity of RadMonteCarlo to the conversion of CT Hounsfield units (HU) to relative stopping power (RSP).MethodsRadMonteCarlo was commissioned from integrated depth-dose (IDD) curves, spot profiles, and absolute-output data for a pencil beam scanning proton system. Three HU-to-RSP assignments were evaluated: a density-derived parameterization, a Bethe–Bloch-based calculation, and a Schneider stoichiometric tissue model. Four anonymized clinical plans (prostate, bladder, lung, and brain) were recalculated. RadMonteCarlo dose was compared with the RayStation Monte Carlo dose, using three-dimensional gamma criteria of 3%/3 mm and 2%/ 2 mm. RadMonteCarlo distributions were also compared directly to isolate RSP sensitivity from TPS agreement.ResultsThe commissioned fits achieved a mean R² of 0.9998, and re-simulated R80 values agreed with the measurements within 1 mm (mean difference +0.39 mm). All 12 clinical plan–RSP comparisons met the specified 95% criterion at 3%/3 mm. In direct RSP model comparisons, target mean-dose differences ranged from−1.15% to +1.20%, distal R80 shifts along the beam axes ranged from−0.3 to +1.9 mm, and the 95th-percentile absolute voxelwise dose difference ranged from 1.8% to 4.1%.DiscussionThese controlled comparisons demonstrate that HU-to-RSP selection produces localized, anatomy- and beam-path- dependent changes in the individual cases examined. RadMonteCarlo therefore provides a stable independent recalculation framework in which calibration-driven effects can be identified and interpreted separately from transport or source-model differences.
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BibTeX
@article{mcnamara2026proton,
title = {{Proton treatment-plan dose verification with a DPM-based Monte Carlo engine}},
author = {Aimee L. McNamara and Daniel O’Brien and Alan Nelson},
journal = {Frontiers in Oncology},
year = {2026},
month = nov,
doi = {10.3389/fonc.2026.1963150},
url = {https://www.frontiersin.org/articles/10.3389/fonc.2026.1963150},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Proton treatment-plan dose verification with a DPM-based Monte Carlo engine
AU - Aimee L. McNamara
AU - Daniel O’Brien
AU - Alan Nelson
PY - 2026
DA - 2026/11/06
JO - Frontiers in Oncology
DO - 10.3389/fonc.2026.1963150
UR - https://www.frontiersin.org/articles/10.3389/fonc.2026.1963150
AB - IntroductionIndependent proton dose verification requires a calculation pathway that is accurate enough to identify clinically relevant discrepancies while remaining practical to commission and operate. We use a pre-release version of the commercial RadMonteCarlo, a multithreaded CPU-based proton Monte Carlo engine built on a dose planning method (DPM) framework for independent treatment-plan recalculation. In this study, we evaluate the sensitivity of RadMonteCarlo to the conversion of CT Hounsfield units (HU) to relative stopping power (RSP).MethodsRadMonteCarlo was commissioned from integrated depth-dose (IDD) curves, spot profiles, and absolute-output data for a pencil beam scanning proton system. Three HU-to-RSP assignments were evaluated: a density-derived parameterization, a Bethe–Bloch-based calculation, and a Schneider stoichiometric tissue model. Four anonymized clinical plans (prostate, bladder, lung, and brain) were recalculated. RadMonteCarlo dose was compared with the RayStation Monte Carlo dose, using three-dimensional gamma criteria of 3%/3 mm and 2%/ 2 mm. RadMonteCarlo distributions were also compared directly to isolate RSP sensitivity from TPS agreement.ResultsThe commissioned fits achieved a mean R² of 0.9998, and re-simulated R80 values agreed with the measurements within 1 mm (mean difference +0.39 mm). All 12 clinical plan–RSP comparisons met the specified 95% criterion at 3%/3 mm. In direct RSP model comparisons, target mean-dose differences ranged from−1.15% to +1.20%, distal R80 shifts along the beam axes ranged from−0.3 to +1.9 mm, and the 95th-percentile absolute voxelwise dose difference ranged from 1.8% to 4.1%.DiscussionThese controlled comparisons demonstrate that HU-to-RSP selection produces localized, anatomy- and beam-path- dependent changes in the individual cases examined. RadMonteCarlo therefore provides a stable independent recalculation framework in which calibration-driven effects can be identified and interpreted separately from transport or source-model differences.
SN - 2234-943X
ER -