Automated quantification of mesenteric hyperaemia in Crohn's disease using time-of-flight magnetic resonance...

Mesenteric hypervascularity ("comb sign") reflects active inflammation in Crohn's disease (CD) but is judged qualitatively on cross-sectional imaging. Despite its clinical relevance, no objective, quantitative MRI-based measures exist to assess this feature. This study aims to develop and evaluate an automated, contrast-free time-of-flight MR angiography (ToF-MRA) method for quantifying mesenteric vascularity in CD by comparing these measurements with healthy controls and assess the method's repeatability and susceptibility to confounding by adiposity or prior bowel resection surgery.

Twenty-three patients with active CD and seventeen healthy controls underwent abdominal ToF-MRA scans. A fully automated pipeline was developed to segment mesenteric vessels on 18 rotating maximum-intensity projections, skeletonised vessels, and count branching points to compute an Arborisation Index. Secondary analyses included a BMI-matched sub-cohort, a prior-resection comparison, and associations with BMI and visceral adipose tissue from Dixon MRI scans. Repeatability was assessed using repeated scans acquired during the same visit.

The Arborisation Index was higher in CD patients than in healthy controls (122.7 ± 37.1 vs. 98.4 ± 24.6; p = 0.02; d = 0.7) and this difference persisted in 10 BMI-matched pairs (145 ± 36 vs. 103 ± 24; p = 0.008; d = 1.4). Prior bowel resection (n = 11) did not influence the measure (p = 0.42). Short-term repeatability was good, with coefficients of variation of 8.9 ± 6% in CD and 8.5 ± 5% in controls. The Arborisation Index showed no significant correlation with BMI or visceral adipose volume.

The Arborisation Index demonstrated significant group-level differences between CD patients and healthy controls, showed good short-term repeatability, and appears technically robust to adiposity and surgical history. Larger longitudinal studies are required to establish its biological meaning, clinical relevance, and responsiveness to inflammatory activity.