S2807
RTT - RTT contouring, target definition, and treatment planning
ESTRO 2026
Conclusion: Using different ROI definitions, high variation was observed with low CA for CTV\GTV. This demonstrates the importance of individualised ROI prioritisation to ensure accurate delineation of soft tissue target volumes. References: (1) Brock, K. K., Mutic, S., McNutt, T. R., Li, H., & Kessler, M. L. (2017). Use of image registration and fusion algorithms and techniques in radiotherapy: Report of the AAPM Radiation Therapy Committee Task Group No. 132. Medical physics, 44(7), e43-e76. Keywords: MRI, image registration, rectal cancer Cutting the cake: Optimising arc and collimator design in comprehensive nodal 5Fx VMAT breast radiotherapy Laura Baker Radiation Oncology Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, Australia Purpose/Objective: As breast radiotherapy (RT) moves toward ultra- hypofractionation, adapting standard techniques is essential. Volumetric Modulated Arc Therapy (VMAT) for comprehensive nodal involvement raises concerns about low-dose exposure to organs at risk (OARs). Our department reevaluated large-arc VMAT approaches Digital Poster 5224 to align with international data1, focusing on minimising exit doses to the heart, contralateral breast, and lungs. This study assesses the impact of shorter arc trajectories combined with collimator angle optimisation on OAR sparing.
Results: 10 patients(M-6;F-4)(70 registrations). CCA scoring for CTV\GTV for all registrations is shown in figure 1. Higher variation in CA was shown for GTV. TM data is reported for registrations in table 1, and shows large variation in ROI especially superior/inferior direction.
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