A service evaluation into the sensitivity of 6 different ROIs used for VMAT breast radiotherapy with SGRT

Campbell-O'Donnell, Roisin and Kirby, Mike ORCID: 0000-0001-9765-5641 (2025) A service evaluation into the sensitivity of 6 different ROIs used for VMAT breast radiotherapy with SGRT [Poster]

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Introduction SGRT is increasingly utilised to facilitate DIBH breast radiotherapy alongside VMAT to further reduce cardiotoxicity. However, SGRT systems such as AlignRT utilise a 3-camera set-up which is intercepted by the gantry and imaging equipment causing interruptions in accurate surface monitoring. This is of particular importance in unstable DIBH treatment positions, where the patient could breathe away during camera occlusions resulting in inaccurate imaging and/or treatment delivery. Ensuring a robust region of interest (ROI) during camera occlusion is imperative for accurate treatment. Although ROIs have been suggested(1-7) there remains a lack of consensus and evidence in the literature to the most appropriate ROI in rotational imaging/treatments. Therefore, this project aimed to examine the sensitivity of ROIs to camera occlusion during CBCT/VMAT arcs. Method As per recommendations from ESTRO-ACROP and AAPM an anthropomorphic female phantom was used(1,3) with a mock left-breast VMAT DIBH plan. Six different ROIs were used with AlignRT based on current clinical practice and literature suggestions. Sensitivity tests were conducted by moving the treatment bed in each translational direction (VERT, LONG, LAT) until the system displayed ‘poor correspondence’. This was conducted at both 0 and 50 degrees for both the CBCT (kV equipment extended) and VMAT arc (kV equipment retracted). Results It is interpreted that larger couch movement before occlusion corresponds with a less sensitive and more robust ROI. ROIs were more sensitive at CBCT 50 in vertical and lateral directions compared to ARC0 due to lateral camera occlusion. In the vertical and lateral directions, larger ROIs were less sensitive and more robust such as ROI_WBHC (whole breast half-contralateral), ROI_WBFC (whole breast full-contralateral) and ROI_WBT (whole breast with tail). ROI_T (inverted-T shape) and ROI_CROSS (X-shape) were more sensitive to couch movements in all directions for arcs/gantry angles. All ROIs were less sensitive to couch movements in the longitudinal direction due to continual monitoring by the central camera. Conclusion Lateral camera occlusion can result in greater sensitivity of ROIs, as demonstrated by comparing results from CBCT50 to ARC0. Therefore, an ROI should be selected that is less sensitive and more robust during camera occlusions. Larger ROIs tended to be less sensitive to camera occlusion in multiple directions compared to the smallest, ROI_T. Overall, this demonstrates that sensitivity should be considered when selecting an ROI to ensure greater tracking during rotational imaging and treatment and that a larger ROI may be more appropriate. References 1. Al‐Hallaq HA, Cerviño L, Gutierrez AN, Havnen‐Smith A, Higgins SA, Kügele M, et al. AAPM task group report 302: Surface‐guided radiotherapy. Med. Phys. 2022;49(4):e82-e112. 2. Bellala R, Kuppusamy A, Bellala V, Tyagi T, Manoharan S, Gangarapu G, et al. Review of clinical applications and challenges with surface-guided radiation therapy. J. Cancer Res. Ther. 2023;19(5):1160-9. 3. Freislederer P, Batista V, Öllers M, Buschmann M, Steiner E, Kügele M, et al. ESTRO-ACROP guideline on surface guided radiation therapy. Radiat. Oncol. 2022;173:188-96. 4. Huijskens S, Granton P, Fremeijer K, van Wanrooij C, Offereins-van Harten K, Schouwenaars-van den Beemd S, et al. Clinical practicality and patient performance for surface-guided automated VMAT gating for DIBH breast cancer radiotherapy. Radiat. Oncol. 2024;195:110229. 5. Li G, Lu W, O'Grady K, Yan I, Yorke E, Arriba LIC, et al. A uniform and versatile surface‐guided radiotherapy procedure and workflow for high‐quality breast deep‐inspiration breath‐hold treatment in a multi‐center institution. J. Appl. Clin. Med. Phys. 2022;23(3):e13511. 6. Sauer TO, Ott OJ, Lahmer G, Fietkau R, Bert C. Region of interest optimization for surface guided radiation therapy of breast cancer. J. Appl. Clin. Med. Phys. 2021;22(10):152-60. 7. VisionRT. MyVisionRT Portal [Internet] 2024 [cited 2024 Oct 27] Available from: https://portal.myvisionrt.com/

Item Type:	Poster
Divisions:	Faculty of Health & Life Sciences Faculty of Health & Life Sciences > Inst. Population Health
Depositing User:	Symplectic Admin
Date Deposited:	17 Mar 2025 16:31
Last Modified:	17 Mar 2025 16:31
DOI:	10.13140/RG.2.2.13297.80484
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3190851
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