Automatic commissioning of a GPU-based Monte Carlo radiation dose calculation code for photon radiotherapy

Area of Science:

• Medical Physics
• Computational Dosimetry
• Radiation Oncology

Background:

• Monte Carlo (MC) simulation is the gold standard for accurate radiation dose calculations in clinical practice.
• Accurate commissioning of MC beam models with clinical linear accelerators is essential for reliable dose prediction.
• Existing commissioning methods can be time-consuming and may lack precision.

Purpose of the Study:

• To develop and validate an automated commissioning method for a GPU-based MC dose engine (gDPM) using phase-space-lets (PSLs).
• To improve the accuracy and efficiency of MC beam model commissioning for clinical implementation.
• To assess the performance of the proposed method across various beam energies and treatment plans.

Main Methods:

• A novel beam modeling approach using phase-space-lets (PSLs), where each PSL represents particles with similar spatial and energy characteristics.
• PSLs were generated from a reference phase-space file, each assigned a weighting factor.
• An optimization problem, solved using an augmented Lagrangian method with symmetry and smoothness regularizations, adjusted PSL weights to match measured dose data.

Main Results:

• The automated commissioning method significantly improved the 3D gamma-index test passing rates for a Siemens 6 MV beam, from 70.56% to 99.36% (2%/2 mm) and 32.22% to 89.65% (1%/1 mm).
• For a head-and-neck IMRT plan, gamma-index passing rates improved from 92.73% to 99.70% (2%/2 mm) and 82.16% to 96.73% (1%/1 mm).
• Validation with real clinical data from Varian, Siemens, and Elekta linear accelerators demonstrated a similar high level of accuracy.

Conclusions:

• The proposed automatic commissioning method using PSLs provides a robust and accurate approach for MC beam modeling.
• This method enhances the clinical applicability of GPU-based MC dose engines like gDPM.
• The technique offers a significant improvement in dose calculation accuracy, crucial for precise radiation therapy delivery.