ESTRO 2025 - Abstract Book

S4077

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

Fig. 2. Correlation between the time (min) of the first and second cone beam CT and the length of the vectorial displacement (cm). The blue dots correspond to each faction.

Conclusion: During oART of prostate cancer, the time elapsed between the two daily CBCT scans had not significantly affected patients' position. The small average displacement during this period can be attributed to proper patient preparation, and comfortable patient positioning. The intra-adaptation time did not change significantly in the examined patients.

Keywords: oart, prostate

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Proffered Paper Enhancing liver SABR: superior CBCT quality and IGRT accuracy with mechanically-assisted breath-holds Julien Pierrard 1,2 , Christel Abdel Massih 2 , Maria Alvear Garcia 2 , Enrique Alvarez Moreno 2 , Andrea Colot 2 , Romain Mony 2 , Ana Francisca Nevez Marues 2 , Thaïs Tison 2 , Valentin Van den Bossche 2 , Aniko Wale Etume 2 , Lamyae Zouheir 2 , Geneviève Van Ooteghem 1,2 1 MIRO, UCLouvain, Brussels, Belgium. 2 Department of radiotherapy, Cliniques Universitaires Saint-Luc, Brussels, Belgium Purpose/Objective: SABR is an effective alternative treatment for liver tumour when surgery is contraindicated [1]. Breathing not only challenges liver SABR due to inherent tumor motion; it also compromises the IGRT images quality, thereby threatening treatment accuracy. Breath-holds were proposed to overcome the respiratory motion [2]. To allow long treatment sessions requested by SABR, we performed breath-holds induced by mechanically-assisted non-invasive ventilation (MANIV-BH). It helps patients to hold their breath for 30 sec repeatedly. Consequently, MANIV-BH may impact CBCT image quality, IGRT and treatment accuracy.

This analysis aimed to compare the image quality of CBCTs acquired using free-breathing (FB) and MANIV-BH for liver SABR. We also evaluated the inter-operator IGRT variability between these FB and MANIV-BH.