Develop the First Dynamic Non-Coplanar Trajectory Optimization Algorithm for an Efficient 4Π Spot-Scanning Proton ARC (SPARC-4Π) Treatment

Document Type

Conference Proceeding

Publication Date

9-2026

Publication Title

International Journal of Particle Therapy

Abstract

Background and Aims: The degree of freedom has been recognized as a key factor in particle beam therapy, such as improving the dose conformity and linear energy transfer distributions. Therefore, proton arc therapy has drawn significant interest in the Society of Radiation Oncology as a potentially efficient and optimal treatment option for cancer patients. However, state-of-the-art spot-scanning proton arc therapy (SPArc) still relies on single or dual- co-planar arc trajectories, which limits its capacity to advance the treatment outcome further. This study aims to develop the first 4π arc optimization algorithm that searches for efficient arc trajectories in 4π space, explores the potential dosimetric improvements, and demonstrates its feasibility through simulation. Methods: Dynamic Programming, originally from control theory, was translated into this new concept of the 4π SPArc optimization algorithm (SPArc-4π) 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 4π 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 using target coverage and organ-at-risk (OAR) sparing. Results: The new SPArc-4πdemonstrated superior dosimetric performance across various evaluation metrics for all three disease sites (Table 1). Figure 1 illustrates the 4π trajectory search and resampling of the control point for dynamic treatment delivery with couch and gantry rotation. The simulation results show that SPArc-4π can be delivered within a reasonable time of approximately 5 to 11 min, comparable to the SPArc-2d plans. Conclusions: The study introduced the first optimization algorithm for SPArc-4π technique. It not only showed SPArc-4π ‘s potential to improve the plan quality via a greater degree of freedom compared to the conventional IMPT and state-of-the-art 2D coplanar SPArc-2d technique but also demonstrated its feasibility for future clinical implementation given the current proton beam therapy system’s machine characteristics.

Volume

21

Issue

Suppl

First Page

101796

Last Page

101796

Comments

PTCOG 64 Particle Therapy Co-Operative Group 64th Annual Conference, June 8-13, 2026, Deauville, France

DOI

10.1016/j.ijpt.2026.101796

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