Fast Positron Distribution Scoring with Mcsquare for PET-Based Proton Range Verification
Abstract
Purpose
Proton range uncertainty limits the precision of proton therapy. While PET-based verification is promising,current modeling methods are computationally inefficiency. This study presents a fast, accurate approach for simultaneous simulation of proton dose and positron emitter distributions by integrating a a proton-induced positron emitter production model into the MCsquare Monte Carlo framework.
Methods
Building upon the MCsquare software, an open-source Monte Carlo simulation platform, this work implements a dedicated positron scoring module within the simulation framework. Activation cross-sections for predominant human tissue elements were curated, focusing on six key reaction channels involving ¹²C, ¹⁴N, and ¹⁶O. Nuclear reaction cross-section tables were established and implemented in the simulation to enable isotope-specific yield calculations. A calculation framework was developed to compute positron production rates from various reaction channels, enabling voxel-wise prediction of positron emission (PE) distributions. The proposed module, termed MC2-PE, was validated against GATE Monte Carlo simulations and experimental PET data acquired from homogeneous phantom irradiations. Quantitative metrics were used to evaluate agreement in dose and positron activity distributions, as well as to compare computational performance between platforms.
Results
The MC2-PE module reproduced dose distributions consistent with those generated by GATE and RayStation, demonstrating high consistency in R80 range. Simulated ¹¹C activity distributions demonstrated strong agreement with in-beam PET measurements, particularly in the distal fall-off region, achieving an average ΔR50 of less than 2 mm. Notably, MC2-PE achieved a 30- to 70-fold reduction in runtime compared to GATE using mathematical phantoms, and even greater acceleration is expected when applied to voxel-based phantoms.
Conclusion
The MC2-PE framework offers a rapid and accurate solution for PET-based range verification. By enabling concurrent dose and isotope calculation with high efficiency, it holds significant potential to enhance treatment precision in clinical workflows. Future work will extend validation to heterogeneous phantoms and patient data.