Fast Pencil Beam Dose Calculation for Proton Therapy Using a Double-Gaussian Beam Model

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Computational Physics

Background:

• Scanned proton pencil beams (PBs) offer conformal dose distributions but are sensitive to motion and anatomical changes.
• Real-time dose calculation is crucial for online dose monitoring in proton therapy.
• Previous work established a GPU-based PB algorithm for online dose calculation.

Purpose of the Study:

• To extend the GPU-based PB algorithm with a double-Gaussian model for improved low-dose halo representation.
• To evaluate the computational cost and accuracy of the extended algorithm for proton therapy.

Main Methods:

• Implemented a double-Gaussian beam model within an existing GPU-accelerated PB algorithm.
• Utilized two parameterizations for the halo dose: literature-based secondary particle distribution and Monte Carlo simulation fitting.
• Assessed the impact on calculation time for treatment plans and energy layers.

Main Results:

• The extended algorithm accurately accounts for the low-dose halo without significant computational overhead.
• Calculation time increased by no more than 16% for investigated plans and ~25% for the most time-consuming energy layers.
• Parameterization choice had minimal impact on calculation time, suggesting broad applicability.

Conclusions:

• The developed GPU-based PB algorithm with a double-Gaussian model is the first of its kind for proton therapy.
• The algorithm enables accurate real-time dose calculation, crucial for online monitoring and adaptive radiotherapy.
• The implementation is adaptable for commercial treatment planning systems, promising improved clinical accuracy.