ESTRO 2026 without replanning. RTT re - optimisation preserved PTV coverage in 9/10 patients; one case required reduced PTV coverage and would need full replanning to restore coverage. Sigmoid position was qualitatively checked but not dosimetrically quantified due to limited CBCT field of view. AI auto - contours required manual RTT edits in all cases. Plan complexity analysis indicated all sCT plans were deliverable without additional PSQA. Ninety - one CBCTs were analysed for potential PoD adoption. Retrospective application of the PoD workflow would have allowed PoD selection in 50/91 fractions (55%), reducing the need for replanning or additional imaging and shortening patient time in department. Conclusion: An RTT - led sCT and AI - supported PoD workflow on non - adaptive linacs is feasible, deliverable, and dosimetrically valuable. By leveraging existing equipment with modern AI tools and empowering RTTs to lead adaptive decision-making, this PoD approach delivers high-value care in resource-limited settings. Prospective validation and integration into
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RTT- RTT operational practice and workflow innovations
al. Accuracy of MRI-CT registration in brain stereotactic radiotherapy: Impact of MRI acquisition setup and registration method. Z Med Phys. 2022;32(4):477-487. doi:10.1016/j.zemedi.2022.04.004 Keywords: Gamma Knife, Radiotherapy, Positioning Digital Poster 4228 Empowering RTTs: A lean synthetic CT-based plan- of-the-day feasibility study for prostate radiotherapy patients with bladder filling challenges Caitriona Kelly 1 , Claire Fitzpatrick 1 , Aodh MacGairbhith 1 , Sinead Brennan 1,2 , Elizabeth Forde 2,3 , Ciaran Malone 1,4 1 Radiation Oncology, St. Luke’s Radiation Oncology Network, Dublin, Ireland. 2 Trinity College Dublin, St James' cancer Institute, Dublin, Ireland. 3 Applied Radiation Therapy Trinity, Discipline of Radiation Therapy, Dublin, Ireland. 4 Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands Purpose/Objective: Bladder filling variability in prostate radiotherapy risks exceeding OAR doses, repeated imaging, increased patient distress and prolonged visits. This study evaluates the feasibility and dosimetric impact of a vendor-neutral, RTT-led, plan-of-the-day (PoD) workflow using both CBCT - derived synthetic CTs (sCT) and AI - assisted contouring on non - adaptive Varian linacs, aiming to create a lean protocol that enables RTTs to manage anatomical variation consistently. Material/Methods: A retrospective review included 10 prostate cancer patients treated to 60 Gy in 20 fractions who had persistent low bladder volumes (bladder < planned for ≥ 3 fractions). Daily CBCTs prompting intervention using the bladder analysis task were converted to sCTs. MVision Contour+ auto - contoured OARs, these were reviewed and edited by RTTs. Rigid registration was used to map PTVs to the sCT. The clinical plan was recalculated in Eclipse v18 and evaluated against CHiPP trial bladder dose - volume constraints (DVCs). If bladder DVCs were exceeded, RTTs re - optimised the plan on the sCT to generate a PoD option. PoD bladder volumes were compared with subsequent fraction CBCTs to assess (1) PoD adoption potential and (2) achievable bladder dose reduction. Results: All on - treatment bladders modelled on sCT exceeded CHiPP bladder constraints; every patient required a PoD to ensure bladder constraints were achieved
clinical pathways are warranted. Keywords: Lean, PoD, adaptive
Digital Poster 4259
Session time saving with optical viewer use in deep inspiration breath hold radiotherapy for left-sided breast cancer Francesca Cucciarelli 1 , Elena Galofaro 1 , Michela Medici 1 , Sara Zitti 1 , Vittoria Emanuela Morabito 2 , Marco Valenti 2 1 Department of Internal Medicine, Radiotherapy Unit, Azienda Ospedaliero-Universitaria delle Marche, Ancona, Italy. 2 Department of Radiological Sciences,
Medical Physics Unit, Azienda Ospedaliero- Universitaria delle Marche, Ancona, Italy
Purpose/Objective: The aim of this study was to evaluate the impact of an optical viewer system in patients undergoing Deep Inspiration Breath Hold (DIBH) radiotherapy for left-
sided breast cancer. Material/Methods:
Forty patients(pts) with left-sided breast cancer underwent whole-breast irradiation in DIBH using a Varian TrueBeam linear accelerator. Planning CT scans were acquired in DIBH, and respiratory motion was monitored in real time through the Real-Time Positioning Management (RPM) Gating System (Varian). Twenty patients (Group 1) were treated before the introduction of the optical viewer guided by
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