Campbell-O'Donnell, Roisin, Kirby, Mike 
ORCID: 0000-0001-9765-5641 and Holt, Dan
(2025)
A service evaluation into camera occlusion using Surface Guided Radiotherapy (SGRT) for VMAT DIBH breast patients.
[Poster]
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Description
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 proposed1,2,3,4,5,6,7 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 both camera occlusion and ROI occlusion occur during CBCT/VMAT arcs for DIBH breast patients using a phantom. Method An anthropomorphic female phantom was used as per recommendations from AAPM and ESTRO-ACROP guidelines1,3 and a VMAT DIBH treatment plan produced. Six different ROIs were drawn using the AlignRT software based on current clinical practice and literature suggestions and tested for full camera occlusion on an Elekta Linac for the CBCT and VMAT arcs. Percentage of surface 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 kV panel and gantry overlap which is not present with the VMAT arc (Figure 2). Conclusion Results demonstrated that ROI occlusion can occur when lateral cameras are blocked particularly between 10-60 degrees for the CBCT arc. The greatest percentage of ROI occlusion at 60 degrees occurred at the superior lateral aspects of the ROIs. Therefore, ensuring adequate inferior and lateral coverage may create a robust ‘monitoring’ ROI and in clinical practice may involve merging aspects of both ROI_T and ROI_WBFC. Further research is required with patient data to establish clinical workflows.
| Item Type: | Poster |
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| Divisions: | Faculty of Health & Life Sciences Faculty of Health & Life Sciences > Inst. Population Health |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 26 Sep 2025 08:21 |
| Last Modified: | 26 Sep 2025 08:21 |
| DOI: | 10.13140/RG.2.2.26287.65442 |
| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3194602 |
| Disclaimer: | The University of Liverpool is not responsible for content contained on other websites from links within repository metadata. Please contact us if you notice anything that appears incorrect or inappropriate. |
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