DOP13 The Arborisation index: An MRI-based measure of mesenteric hyperaemia in Crohn’s Disease

Abstract

Abstract Background Robust and sensitive therapeutic targets are key in effective management of Inflammatory Bowel Disease1. Mesenteric hyperaemia is a recognized sign of active disease and in cross-sectional image is described as the comb sign. Although it is subjectively described, no automated quantitative MRI-based measures have been developed. We aim to develop an automated methodology using contrast-less time of flight (TOF) Magnetic resonance angiography (MRA). Methods A MATLAB algorithm was developed to track the vessels on a 3D maximum intensity projection of a TOF MRA data set and calculate an arborization Index which is the number of branching points in the intrabdominal vessels (figure 1). 2D TOF scans were acquired in the transverse plane between the top of the hip joint and L4 vertebra using a 3T Ingenia Wide bore scanner (Philips, The Netherlands). The primary outcome was a comparison of the arborization index between Crohn’s disease (CD) and healthy volunteers (HV) groups. A planned sub-analysis was undertaken across CD and HV matched for BMI to investigate the effect of visceral fat on the arborization index. Repeated measures were undertaken to evaluate the variability of the quantification method. No contrast agents were used for the TOF MRA scans. Biological variations within each group and test-retest repeatability were assessed using the coefficient of variation (CV). Statistical analysis with unpaired, two-tailed t-tests were conducted and differences were considered significant when the p-value ≤0.05. All absolute values are presented as mean ±standard deviation (SD). Results In this prospective pilot study, 7 CD patients (C-Reactive Protein=5.2±6.1 mg/L, Faecal Calprotectin 611±981μg/g, BMI=23±3 kg/m2) and 15 HVs (BMI=29±7 kg/m2) were recruited. Patients showed a significantly higher arborization index when compared to HVs (mean arborization in HV=94±21 and CD=139±26; p-value=0.002). The difference in arborization index persisted in a sub-analysis of 7 HVs (BMI=24±2 kg/m2) and 7 CD patients (mean arborization in matched HVs=101±22 vs mean index in CD=139±26; p=0.01) (Figure 2). The CV was 23% for HVs and 18% for CD indicating biological variation. Test-retest variability calculated from multiple TOF scans of the same subjects gave a mean CV of 6±5% for both groups combined. Conclusion Our preliminary data suggest that the arborization index may be a useful measure of hypervascularity and hence intestinal inflammation in Inflammatory Bowel Disease. Further validation to standard disease activity measures is needed across larger cohorts to better investigate the utility of this potential biomarker as a non-invasive measure of disease activity and its reversibility to IBD therapies. Reference 1.Turner,D.,et al.Gastro.2021;160(5):1570–1583.