Work

Develop the First Dynamic Non-coplanar Trajectory Optimization Algorithm for an Efficient 4π Spot-scanning Proton Arc (sparc-4π) Treatment Delivery

Year: 2026

Type: article

Abstract: Background and Aims: FLASH radiation therapy, which generates FLASH effect through ultra-high-dose-rate (UHDR) radiation, has demonstrated promising performance in lowering the risk on healthy organs of patients while fulfilling treatment goals.However, the achievement of proton FLASH effect is affected by a wide variety of factors, including patient-specific range modulators (PSRMs) in the practical setup, and the scanning path within a specific field.This research work is aimed at designing a new one-step dose-conformal treatment planning algorithm to jointly optimize spot weights, PSRM shapes, and scanning path, so as to achieve better proton FLASH effect coverage and achievement in treatment. Methods:The proposed algorithm employs a two-level optimization structure, and separates the overall problem into an inner problem and an outer problem.In the inner problem, the algorithm fixes the scanning path and alternately optimizes between spots weights and PSRM shapes utilizing the alternating direction method of multipliers (ADMM).In the outer problem, the algorithm fixes spot weights and PSRM shapes, and optimize the scanning path using a custom genetic optimization algorithm.The inner and outer problem optimization processes are alternately performed to ensure convergence.Results: Experimental results indicate that the proposed algorithm consistently outperforms the baseline Joint Range-Modulator and Spot Optimization (JSRO) approach, which optimizes only spot weights and PSRM shapes, with particularly pronounced gains observed in lung cases.In the first lung case, dose-rate coverage increases from 38.05% to 70.09%, while FLASH effect coverage improves from 28.54% to 47.05%.In the second lung case, dose-rate coverage increases from 49.38% to 64.43%, while FLASH effect coverage improves from 36.34% to 45.49%.Beyond coverage improvements, the proposed method also reduces the maximum target dose and yields a higher conformity index (CI), demonstrating enhanced dose conformity and overall plan quality.Conclusions: This research work proposes a new one-step doseconformal treatment planning algorithm that optimizes spot weights, PSRM shapes, and scanning path simultaneously, and achieves better proton FLASH effect achievement compared to baseline counterparts.

Source: International Journal of Particle Therapy

DOI: 10.1016/j.ijpt.2026.101796