S2887
RTT - RTT education, training, and advanced practice
ESTRO 2026
structure comparison and dosimetry metrics, streamlining the pathway for the safe and effective introduction of hippocampus sparing radiotherapy. Material/Methods: Ten patient datasets were anonymised. Guideline based segmentation using Contour+ (MVISION AI Inc.) of left and right hippocampi on 1.25 mm post-contrast axial T1 MRI slices (Siemens Magnetom Sola 1.5T) was carried out. Four CNS radiation oncologists (ROs) reviewed and edited the AI generated hippocampal contours according to RTOG0933. The RO reviewed contours were compared against the MVISON raw AI contours using MVISION Guide & Verify (Surface Dice at 1mm, (sDCE1mm)), (Hausdorff distance, (HD)), and a python script (Average surface distance, (ASD)). The imported segmentations and MRI were then automatically registered to the patients CT dataset in Eclipse v18.1 (Varian Medical Systems, Palo Alto, CA, USA). Dose comparisons were made by overlaying the contours onto a standard HA-WBRT plan prescribed to 30Gy in 10 fractions using VMAT delivery. Results: RO agreement was strong for the AI hippocampal contours with contours measuring > 0.95 sDCE1mm (all but one > 0.99). ASD was < 1mm for all except one case, HD was 0 for all except one case (3 mm). Dosimetric results are summarised in Table 1. There were no or only minor adjustments made in the majority of cases (7/10). However, minor RO edits correlated with substantial dosimetric differences in three cases: Case 1, RO edits to superior left hippocampus added an extra 3.3 Gy to Dmax; Case 9, RO addition of one extra slice added an extra 3.0 Gy and 2.0 Gy to superior left and right hippocampi, respectively; Case 10, two ROs added one extra slice to superior left hippocampus adding 2.2 Gy and 2.4 Gy to Dmax.
Conclusion: The use of the optical viewer during DIBH radiotherapy promotes active and more effective patient participation, improves breath-hold reproducibility, and reduces overall treatment time. These findings support its routine implementation as a practical visual feedback tool to enhance workflow efficiency and patient experience in left-sided breast radiotherapy. Keywords: optical viewer, breath hold, breast cancer RTT led quality improvement project establishing a pathway for automated hippocampal contouring for hippocampal sparing radiotherapy Linda Walshe 1 , David Fitzpatrick 1 , Nazmy ElBeltagi 1 , Oleksandr Boychak 1 , Palak Sharma 1 , Christina Skourou 1 , Claire Fitzpatrick 1 , Sarah McDermott 1 , Gerry Hanna 2 , Ruth Woods 1 , Ciaran Malone 1 1 Radiation Oncology, St Luke's Radiation Oncology Network, Dublin, Ireland. 2 St James's Cancer Institute, Trinity College Dublin, Dublin, Ireland Proffered Paper 4261 Purpose/Objective: The RTOG0933 study showed a reduction in impaired memory and verbal learning demonstrating that hippocampus avoidance whole brain radiotherapy (HA-WBRT) is an alternative option for patients with good performance status (1). However, manual hippocampal contouring can be time consuming and complex, requiring significantly more resources than WBRT. Automated and streamlined pathways are essential to reduce time burden and ensure consistency and accuracy. This study, led by a radiation therapist (RTT) aimed to robustly quality assure AI generated hippocampal contours using both
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