ESTRO 2025 - Abstract Book

S4317

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

Conclusion: AIseg offered substantial and significant improvements in RT-led contouring efficiency and staff time savings for all patient groups apart from the breast cohort. Greatest time saving was seen for cohorts with the largest numbers of OARs. While RTs saved time, enabling them to focus on other responsibilities, the timeline for this workflow component from task availability to completion, or from planning-CT to treatment commencement, was not reduced. Continued collaboration and re-evaluation of clinical processes are needed alongside AIseg adoption to ensure innovations lead to measurable improvements in efficiency and reduced patient waiting times.

Keywords: AI segmentation, workflow impact, MDT evaluation

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Mini-Oral A fast, RTT-led workflow for long-scheme treatments on the MR-Linac: Adapt-to-shape Lite Roel Bouwmans, Maartje M.C. Schoenmakers, Koen M. Kuijer, Matteo Maspero, Gert J. Meijer, Martijn P.W. Intven, Stella Mook Radiotherapy, UMC Utrecht, Utrecht, Netherlands Purpose/Objective: Online adaptive MRI-guided radiotherapy (MRgRT) is commonly used in hypo-fractionated treatments. Its application in long-scheme treatments (>15 fractions) is limited due to prolonged fraction durations, making daily online adaptive treatment less feasible. To overcome this problem a simplified workflow, called Adapt-to-Shape-Lite (ATS-Lite), was designed for long-scheme MRgRT. This abstract describes the first experience with this new MRgRT workflow for rectal and esophageal cancer patients. Material/Methods: The ATS-Lite workflow, conducted on a 1.5-T MR-Linac (Unity, Elekta AB, Sweden), is an online adaptive process led by radiation therapists (RTTs), utilizing deformable propagated delineations from the treatment planning system (Monaco 6.2.1, Elekta AB, Sweden). Patients treated with a long-scheme radiotherapy were eligible for ATS-Lite if the clinical target volume (CTV) did not exceed 18 cm and they met MRI safety criteria. The workflow consisted of four steps (Figure 1): 1. Imaging : Online MRI is acquired 2. Match, deform contours and check: The MRI is matched to the pre-treatment MRI using a clipbox. Deformed contours are propagated on the new MRI and assessed for clinical usability by RTTs. Contours are no longer fully adjusted manually, but only adapted in case target coverage is compromised. 3. Plan Calculation: IMRT treatment plan is optimized based on new contours 4. Irradiation: Thanks to the faster workflow, treatment begins without further position verification. At the end of the dose delivery, a post-MRI is acquired simultaneously with irradiation to assess intrafraction motion. RTTs recorded the total treatment time and time per step. The time between steps was classified as miscellaneous.