ESTRO 2025 - Abstract Book

S3209

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

Results: Differences of up to 5 Gy were observed for the airway D0.1 cm³, with an average difference of 0.5 ± 1.2 Gy. Notably, 28% of patients experienced differences exceeding 2 Gy in airway PRV D0.1 cm³, while 17% saw differences of over 3 Gy, with an average difference of 0.95 ± 1.7 Gy. An average dose change of 2 Gy per mm of airway motion was found. The largest dose discrepancies occurred in cases where tumours were located inferior to the 1st order bronchi (see Figure 2), especially where breathing motion was greater than 6 mm. This approach revealed that five of the eighteen patients' treatment plans exceeded a DVC limit, necessitating further clinical evaluation and potential replanning.

Conclusion: The study highlights the importance of accounting for airway movement in central and ultra-central lung SABR, as a 5mm airway PRV may not be suitable in all cases, particularly where breathing motion is large and for tumour locations inferior to the central airways. Given that five patients' plans exceeded DVC limits when airway motion was considered, incorporating an internal risk volume concept for the airway could improve normal tissue dose estimates and patient safety in lung SABR treatment planning.

Keywords: Ultra-central Lung, SABR, Airways

References: [1] Karin Lindberg et al. “The HILUS-trial—A prospective Nordic multicenter phase 2 study of ultracentral lung tumors treated with stereotactic body radiotherapy”. In: Journal of Thoracic Oncology 16.7 (2021), pp. 1200–1210.

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Mini-Oral ECG-gated cardiac CT based patient- and segment-specific cardiac motion estimation for stereotactic arrhythmia radioablation in the RAVENTA framework Jingyang Xie 1 , Alicia S. Bicu 2,3 , Melanie Grehn 4 , Mustafa Kuru 5 , Adrian Zaman 6 , Xinyu Lu 1 , Christian Janorschke 1 , Jens Fleckenstein 2,3 , Marcus Both 7 , Stephan Hohmann 8,9 , Egor Borzov 10,4 , Roland R. Tilz 11,12 , Dirk Rades 13 , Frank A. Giordano 2,3 , Daniel Buergy 2,3 , Boris Rudic 14,15 , David Duncker 8 , Roland Merten 16 , Tomer Charas 10 , Mahmoud Suleiman 17 , Evgeny Lian 6 , Achim Schweikard 1 , Oliver Blanck 4 , Judit Boda-Heggemann 2,3 , Lena Kaestner 2,3