Develop a Novel Non-Coplanar Trajectory Optimization Algorithm for an Efficient 4pi Spot-Scanning Proton Arc (SPArc-4pi) Treatment Delivery
Abstract
Purpose
This study aims to develop the first 4pi dynamic proton arc optimization algorithm which searches for efficient arc trajectories in 4pi space, explores the potential dosimetric improvements in multiple disease sites. Then we demonstrate its feasibility through simulation using a clinical proton therapy system.
Methods
Dynamic Programming, originally from control theory, was translated into this new concept of the 4π SPArc optimization algorithm (SPArc-4pi) for the trajectory search and route decision-making. It breaks down the complicated and high-computational-demand main problem into a series of small sub-problems and searches for delivery-efficient 4pi arc trajectories through an iterative approach. Three different disease sites, e.g., head & neck, partial brain, and clival brain chordoma, were used for testing purposes. Conventional Intensity Modulated Proton Therapy (IMPT) and 2D co-planar arc (SPArc-2d) plans were generated as a benchmark. Treatment delivery efficiency was evaluated through a published and validated dynamic arc system controller. Plan quality was assessed through target coverage and organ at risk (OAR) sparing.
Results
The new SPArc-4pi demonstrated superior dosimetric performance across various evaluation metrics for all three disease sites. The simulation result shows that SPArc-4pi is able to be delivered within a reasonable time of around 5 to 11 mins, which is comparable to the SPArc-2d plans.
Conclusion
The study introduced the first optimization algorithm for SPArc-4pi technique. It not only showed SPArc-4pi ‘s potential to improve the plan quality via a greater degree of freedom compared to the conventional IMPT and state-of-art 2D co-planar SPArc-2d technique but also demonstrated its feasibility for future clinical implementation based on the current proton beam therapy system’s machine characteristics.