S2754
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
applying the same rules, to verify the observed shifts in clinical setting. Results: Lateral shifts of the spine-isocentres relative to the matched skull-isocentre exceeded the clinically allowed 3mm threshold in all six patients (mean±SD, 4±3 mm; in combination with maximal 1° yaw). Sufficient target coverage was achieved with D98 CTV >97.4%. No under- or overdosage was observed in the junction areas (HI planned vs. recalculated 1.1±0.3 vs. 1.1±0.5 Gy). For the 19 clinical fractions evaluated, in seven fractions the lateral shift was >3mm, and in that case, repositioning took 2-5 minutes. Conclusion: IMPT junctions for CSI can be robust for lateral shifts up to 7mm and rotations up to 1°. Allowing restricted individual isocentre positioning showed adequate dose within the entire CTV, without having to reposition the patient. In this way, patient alignment can be more accurate, efficient and patient-friendly.
Integrating telemedicine tools into prostate radiotherapy is both feasible and beneficial for improving preparation quality and patient experience. The adoption of a digital system for managing and monitoring daily preparations represents a promising step toward optimizing the radiotherapy workflow. Keywords: Bladder/rectal preparation, telemedicine, prostate
Digital Poster Highlight 4626
Feasibility of individual isocentre positioning in robustly optimized IMPT of the cranio-spinal axis Sabine Visser, Tirza Faassen-van Loenen, Carol McKenna, Hiske L. van der Weide, Liset L. van den Berg, John H. Maduro, Johannes A. Langendijk, Stefan Both, Charlotte Brouwer, Arnout van der Borden Radiotherapy, UMCG, Groningen, Netherlands Purpose/Objective: Plans with multiple isocentres making use of the maximal field size are necessary in cranial-spinal irradiation (CSI). In our proton clinic, after patient alignment with surface guidance we perform couch shifts based on position verification (PV) of the first isocentre (skull) and then manual reposition the patient for other isocentres (spine) to meet the set-up tolerances (3mm), based on orthogonal kV imaging. In this work, we evaluate whether our CSI IMPT plans allow for couch shifts based on PV for each isocentre individually, aiming for a more efficient process by reducing the need for manual repositioning. Material/Methods: For six CSI patients (2-3 isocentres, junction lengths 3- 6 cm), who underwent a verification CT during treatment (due to positioning problems and weight changes), PV per isocentre was simulated retrospectively and IMPT plans were recalculated. Treatment plans were made with posterior (spine-CTV) and posterior-oblique fields (skull-CTV) [Figure 1], and robustly optimized with 3mm setup and 3% range uncertainty to the OTV, consisting of an additional 3mm margin to the spine-CTV. During PV (planning CT- verification CT), the following rules were applied based on initial testing and beam arrangement considerations: superior-inferior and anterior- posterior shifts were determined by the skull- isocentre, lateral shifts were allowed per isocentre, pitch was allowed for the skull-isocentre and yaw was allowed for the spine-isocentres (both up to ±1°). In the recalculations, CTV coverage (D98) and dose homegeneity (HI[D2-D98]) in the junction areas were evaluated. For 19 fractions of five CSI patients, we repeated PV of the first image of the caudal isocentre (orthogonal kV) after the skull-isocentre was verified,
Keywords: CSA, IMPT, position verification
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Radiographer-Led Development of Immobilisation and Workflow for MR-Guided Stellate Ganglion Radiotherapy Alexander J Goodman 1 , Roxanne Clelland 1 , Emmie Rukoni 1 , Nash Mahleki 1 , Ben George 1 , Ami Sabharwal 1,2
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