Technical Feasibility of Quantitative Measurement of Various Degrees of Small Bowel Motility Using Cine Magnetic Resonance Imaging

Abstract

Objective: Cine magnetic resonance imaging (MRI) has emerged as a noninvasive method to quantitatively assess bowel motility. However, its accuracy in measuring various degrees of small bowel motility has not been extensively evaluated. We aimed to draw a quantitative small bowel motility score from cine MRI and evaluate its performance in a population with varying degrees of small bowel motility.

Materials and methods: A total of 174 participants (28.5 ± 7.6 years; 135 males) underwent a 22-second-long cine MRI sequence (2-dimensional balanced turbo-field echo; 0.5 seconds per image) approximately 5 minutes after being intravenously administered 10 mg of scopolamine-N-butyl bromide to deliberately create diverse degrees of small bowel motility. In a manually segmented area of the small bowel, motility was automatically quantified using a nonrigid registration and calculated as a quantitative motility score. The mean value (MV) of motility grades visually assessed by two radiologists was used as a reference standard. The quantitative motility score's correlation (Spearman's ρ) with the reference standard and performance (area under the receiver operating characteristics curve [AUROC], sensitivity, and specificity) for diagnosing adynamic small bowel (MV of 1) were evaluated.

Results: For the MV of the quantitative motility scores at grades 1, 1.5, 2, 2.5, and 3, the mean ± standard deviation values were 0.019 ± 0.003, 0.027 ± 0.010, 0.033 ± 0.008, 0.032 ± 0.009, and 0.043 ± 0.013, respectively. There was a significant positive correlation between the quantitative motility score and the MV (ρ = 0.531, P < 0.001). The AUROC value for diagnosing a MV of 1 (i.e., adynamic small bowel) was 0.953 (95% confidence interval, 0.923-0.984). Moreover, the optimal cutoff for the quantitative motility score was 0.024, with a sensitivity of 100% (15/15) and specificity of 89.9% (143/159).

Conclusion: The quantitative motility score calculated from a cine MRI enables diagnosis of an adynamic small bowel, and potentially discerns various degrees of bowel motility.

Keywords: Bowel; Cine imaging; Gastrointestinal motility; Magnetic resonance imaging; Small intestine.

Fig. 1. Overview of the small bowel segmentation and motility score calculation. In a manually segmented area of the small bowel, motility was automatically quantified using a nonrigid registration and calculated as a quantitative motility score. MRI = magnetic resonance imaging, MR = magnetic resonance

Fig. 2. The confusion matrix regarding the qualitative grade of small bowel motility determined by two independent readers. The darkest green cells denote concordant cases between the two readers. Notably, there is no case with two-grade differences between the two readers (denoted lightest green cells). Grade 1, adynamic (non-peristaltic) wave; grade 2, decreased but preserved peristalsis; and grade 3, normal peristalsis.

Fig. 3. Scattered box plot of motility scores according to the mean value of grade (A) and consensus grade (B). Determined based on the qualitative analyses by two readers using the following criteria: grade 1, adynamic (non-peristaltic) wave; grade 2, decreased but preserved peristalsis; and grade 3, normal peristalsis.