Author: Laura Bennett, Wesley S. Culberson, Albert Du, Kevin J. Erhart, Ryan T. Flynn, Ryan Gardner, Alonso N. Gutierrez, Patrick M Hill, Daniel E. Hyer, Eric Jensen, Kaustubh A. Patwardhan, Blake R. Smith, Nhan Vu, Karsten K. Wake 👨🔬
Affiliation: University of Wisconsin, Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin - Madison, Miami Cancer Institute, Baptist Health South Florida, Department of Human Oncology, University of Wisconsin School of Medicine and Public Health, Ion Beam Applications (IBA), University of Iowa, Iowa Health Care, .decimal 🌍
Purpose: To develop and experimentally validate a novel Monte Carlo (MC) framework designed to enable calculation-based quality assurance (QA) for collimated intensity modulated proton therapy treatment plans in an automated fashion. This framework automates the conversion between the pencil beam scanning layer delivery (PLD) file for an IBA proton therapy system to Geant4 input, allowing for accurate and efficient MC simulations of clinical treatment deliveries.
Methods: A total of six patient treatment fields were optimized for both uncollimated and energy-specific collimation with the dynamic collimation system (DCS) using the Astroid treatment planning system (TPS). Patient-specific treatment verification was performed by delivering each field with a pre-clinical prototype DCS and beam controller that was integrated with the IBA delivery system at the Miami Cancer Institute. Dose distributions were measured using a high-resolution measurement technique with the IBA MatriXX detector. For each treatment, the composite delivery was simulated in Geant4 from the PLD files that were exported from the TPS and executed on the clinical delivery system. The number of histories varied between 3x107 to 7x107, resulting in <0.1% uncertainty in voxels with over 1% max dose. Simulations were parallelized across twenty-three 2.40 GHz Intel processors.
Results: Total simulation times ranged from one to three hours with an execution rate of 6.5x103 (+/- 78) histories per second. Excellent clinical agreement was observed for both collimated and uncollimated treatment deliveries. The average gamma pass rate (2%, 3 mm, 10% low-dose threshold) was 99.33% (+/- 0.37%) and 97.91% (+/- 1.14%) for uncollimated treatments and DCS-collimated treatments, respectively.
Conclusion: An MC framework was validated for the simulation of energy-specific collimated proton treatment plans that are deliverable from a DCS, enabling MC dose calculations as part of the QA process.