S2259
Physics - Intra-fraction motion management and real-time adaptive radiotherapy
ESTRO 2026
of about 200 frames each. Deformable image registration was used to quantify the motion of the chest wall, diaphragm, and internal vessels. PCA was applied to extract the principal direction of motion (PC1) and the hysteresis component (PC2). The Jacobian determinant was also analysed to identify patterns of respiratory expansion and contraction across the cohort.
Figure 2: Cumulative VOICE distribution for all fraction Conclusion: Liver MRIgRT achieved efficient gated dose delivery using a small gating envelope. Audit-log-based motion analysis confirmed the CMM system’s capability to dynamically manage target displacement and maintain consistent target coverage under abdominal compression. Keywords: MRIgRT, Intrafraction Motion Management, Liver Respiratory Motion Analysis for the Thoracic Region in the Upright and Supine Postures Chung Tin Lo 1 , Michael Kissick 2 , Niek Schreuder 2 , Tracy Underwood 1,2 , Jamie R McClelland 1 1 UCL Hawkes Institute, UCL, London, United Kingdom. 2 Research Department, Leo Cancer Care Ltd, Crawley, United Kingdom Purpose/Objective: Interest in upright, gantry-less radiotherapy has grown, primarily because it promises cost savings by rotating an upright patient through a fixed treatment beam, which reduces shielding demands and Proffered Paper 3923 mechanical complexity[1]. However, data is currently lacking on anatomical and physiological changes between upright and supine body postures. As thoracic RT treatment depends heavily on motion management and understanding breathing dynamics, we were motivated to study posture-induced differences in respiratory motion, to consider the likely impact of upright positioning on thoracic treatments. Material/Methods: A pipeline was developed to analyse respiratory motion differences in a cohort of healthy volunteers (n=10). Volunteers were imaged using 2D Cine MR on a 0.6T multi-position scanner (FONAR) in both upright and supine postures. Each acquisition spanned approximately 14 breathing cycles, yielding two series
Results: A paired t-test showed that mean diaphragm motion (PC1) amplitudes were statistically smaller upright versus supine (p=0.0083). No statistical significance was observed between upright and supine chest wall motion amplitudes.Internal vessel motion was assessed using PC1 and PC2 of the motion trace, representing primary motion magnitude and hysteresis (nonlinear deviation), respectively. For PC1, both the mean and standard deviation of the internal vessel motion amplitude were lower in the upright position (p=0.01 and p=0.02, respectively). However, PC2 showed no statistically significant difference between upright and supine conditions for either the mean or the standard deviation.Analysis of expansion and contraction patterns from the average Jacobian Determinant revealed considerable inter-individual variability, with no consistent trends across participants.
Made with FlippingBook - Share PDF online