Retrospective review of patient factors impacting free-breathing respiratory motion magnitude for MR-guided radiotherapy.

Patient factors may influence motion management strategy selection for abdominal stereotactic ablative radiotherapy (SABR). This retrospective evaluation investigated the impact of body mass index (BMI), sex, and cirrhosis in 16 patients imaged with cine-magnetic resonance imaging (MRI) on a 1.5 T magnetic resonance linear accelerator (MR Linac). Male patients, those with cirrhosis, and higher BMI tended to exhibit greater motion magnitude, although this was not statistically significant, suggesting that these patients should be prioritised for motion management strategies. Further investigation in larger cohorts is warranted to confirm these trends and guide personalised motion management in abdominal radiotherapy.