A First Quantitative Evaluation of Plan Quality Effects From Gantry Rotational Error on Spot-Scanning Arc Therapy (SPArc)

Document Type

Conference Proceeding

Publication Date

10-2024

Publication Title

International Journal of Radiation Oncology, Biology, Physics

Abstract

Purpose/Objective(s): To quantitatively assess the plan quality impact from the random gantry rotational error during the treatment delivery of spot-scanning arc (SPArc) therapy. Materials/Methods: To simulate random gantry rotational error and its associated dosimetric perturbations, the gantry angle of each control point from the nominal SPArc treatment plans was modified using an in-house script. Twelve cases from different disease sites, including brain, lung, liver, and prostate, were selected in this study. The original SPArc plans (SPArcorig) were developed through iterative processes, including control point re-sampling, redistribution of control points & energy layers, energy layer filtration, and re-sampling. Considering unpredictable limitations, rotation errors of 1deg and 2deg were randomly applied to all SPArcorig nominal plans to generate the perturbed dose, simulating the random gantry delivery error during the dynamic treatment. Two kinds of random error were introduced in the gantry error with (SPArcGS) and without Gaussian distribution (SPArcR). The effects on SPArc plans were evaluated using dosimetric parameters and the gamma-index passing ratio (GPR). Results: GPR results are presented in Table 1. For randomized rotational error of 1deg and 2deg, SPArc plans demonstrated GPRs exceeding 96% for both 3%/3mm and 2%/2mm measurement criteria. Remarkably, SPArc plans maintained a GPR of 93.01%§6.12% even under the strictest measurement criteria of 1%/1mm for 1deg error. For rotation errors of 1deg and 2deg with Gaussian distribution, SPArc plans achieved acceptable outcomes, with GPRs of 99.99%§0.02%/99.97%§0.05% and 99.78%§0.33%/ 98.91%§ 0.73% for 1mm/1%, 2mm/2% criteria, respectively. Besides, the dose coverage differences of target between SPArcorig and SPArcGS1mm/2mm are 0.78%§0.83%, 3.2%§1.4%. Conclusion: This is the first quantitative study investigating the robustness of SPArc therapy treatment against gantry rotational error. The data provides a valuable reference for future investigation of quality assurance and measurement in the clinical implementation of SPArc therapy.

Volume

120

Issue

2S

First Page

e158

Comments

ASTRO 2024: 66th Annual Meeting American Society for Radiation Oncology, September 29- October 2, 2024, Washington, DC

DOI

10.1016/j.ijrobp.2024.07.2139

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