ESTRO 2025 - Abstract Book

S4292

RTT - Service evaluation, quality assurance and risk management

ESTRO 2025

2354

Poster Discussion A service evaluation into camera occlusion using Surface-Guided Radiotherapy (SGRT) for VMAT DIBH breast patients. Roisin C Campbell-O'Donnell 1 , Mike Kirby 2 1 Radiotherapy, The Christie NHS Foundation Trust, Manchester, United Kingdom. 2 School of Health Sciences, University of Liverpool, Liverpool, United Kingdom Purpose/Objective: SGRT is used for the treatment of DIBH breast radiotherapy patients. More advanced radiotherapy techniques, such as VMAT are also now utilised alongside SGRT DIBH to further reduce radiation-induced cardiotoxicity. However, issues can present for continuous surface monitoring of these patients due to camera occlusion by the gantry and imaging equipment during rotational imaging and treatment delivery. This creates uncertainty in monitoring the patient’s surface, particularly in unstable DIBH positions where there is a risk that the patient could move or exhale during camera occlusions. Therefore, the most robust region of interest (ROI) should be determined for this patient cohort. Although ROIs for rotational treatments have been proposed 1-6 there remains a lack of evidence for this specific patient cohort within the literature and SGRT forums. Therefore, the objectives of this project were to determine where camera occlusion and ROI occlusion occur during CBCT/VMAT arcs for DIBH breast patients using a phantom. Material/Methods: An anthropomorphic female phantom was used as per recommendations from AAPM and ESTRO-ACROP guidelines 1,3 and a VMAT DIBH treatment plan produced. Six different ROIs were drawn using the AlignRT software based on current clinical practice and literature suggestions 1-6 and tested for full camera occlusion on an Elekta Linac for the CBCT and VMAT arcs. Surface percentage ROI occlusion was measured using Sketch and Calc software and gantry angles of camera occlusion recorded using postural camera view. Results: No evidence of full camera occlusion was demonstrated using an anthropomorphic phantom. Percentage surface area results showed that the largest ROI occlusion occurred for all ROIs during the CBCT at 60 degrees at the superior lateral aspects of ROIs (Figure 1). ROI_T displayed a low percentage ROI occlusion for the majority of CBCT gantry angles. Additionally, the greatest probability of camera occlusion was between gantry angles of 10-60 degrees for the CBCT due to the imaging equipment and gantry overlap which is not present during the VMAT arc (Figure 2).