The challenge of segmental small bowel motility quantitation using MR enterography

Objective: Analysis of cine MRI using segmental regions of interest (ROIs) has become increasingly popular for investigating bowel motility; however, variation in motility in healthy subjects both within and between scans remains poorly described. Methods: 20 healthy individuals (mean age, 28 years; 14, males) underwent MR enterography to acquire dynamic motility scans in both breath hold (BH) and free breathing (FB) on 2 occasions. Motility data were quantitatively assessed by placing four ROIs per subject in different small bowel segments and applying two measures: (1) contractions per minute (CPM) and (2) Jacobian standard deviation (SD) motility score. Within-scan (between segment) variation was assessed using intraclass correlation (ICC), and repeatability was assessed using Bland-Altman limits of agreement (BA LoA). Results: Within-scan segmental variation: BH CPM and Jacobian SD metrics between the four segments demonstrated ICC R = 0.06, p = 0.100 and R = 0.20, p = 0.027 and in FB, the CPM and Jacobian SD metrics demonstrated ICC R = 20.26, p = 0.050 and R = 0.19, p = 0.030. Repeatability: BH CPM for matched segments ranged between 0 and 14 contractions with BA LoA of 68.36 and Jacobian SD ranged between 0.09 and 0.51 with LoA of 60.33. In FB data, CPM ranged between 0 and 10 contractions with BA LoA of 67.25 and Jacobian SD ranged between 0.16 and 0.63 with LoA = +/- 0.28. Conclusion: The MRI-quantified small bowel motility in normal subjects demonstrates wide intersegmental variation and relatively poor repeatability over time. Advances in knowledge: This article presents baseline values for healthy individuals of within-and between-scan motility that are essential for understanding how this process changes in disease.