ESTRO 2024 - Abstract Book

S4858

Physics - Quality assurance and auditing

ESTRO 2024

1 William Beaumont University Hospital, Corewell Health, Department of Radiation Oncology, Royal Oak, USA. 2 Union Hospital, Department of Radiation Oncology, Wuhan, China. 3 Stanford University, Department of Radiation Oncology, Stanford, USA

Purpose/Objective:

Proton beam therapy is sensitive to the gantry angle error as it results in the proton range uncertainties from trajectories deviated from the nominal gantry angles.[1] As spot-scanning proton arc therapy (SPArc) enables dynamic rotational gantry while irradiating the proton spot continuously [2], gantry angle error might happens during the treatment delivery, resulting in unnecessary dosimetric perturbations. In this study, we aim to quantitatively investigate such impact from gantry rotation perturbation in the SPArc therapy.

Material/Methods:

To investigate the dosimetric impact, a series of random gantry rotational errors are introduced in the nominal SPArc plans (SPArc -nominal ). More specifically, random errors of 1degree and 2degree rotation perturbation with and without Gaussian distribution were applied in the original SPArc -nominal , or called perturbed SPArc plan (SPArc -Gaussian perturbed and SPArc -non-Gaussian perturbed ). Four disease sites, including brain, lung, liver and prostate cancer, were selected to evaluate the dosimetric impacts quantitatively. The original SPArc -nominal plans were generated with SPArc algorithm published in 2016 with a 2.5-degree sampling frequency. Dosimetric metrics e.g., DVH and gamma passing ratio (GPR) are used to evaluate dosimetric impact between the nominal and perturbed plans.