Dynamic MRI for bowel motility imaging–how fast and how long?

Catharina S de Jonge,Stuart A Taylor,David Atkinson,Jaap Stoker,Ruaridh M Gollifer,Alex Menys,Aart J Nederveen

doi:10.1259/bjr.20170845

Catharina S de Jonge, Stuart A Taylor + Show 5 more

Open Access

https://doi.org/10.1259/bjr.20170845

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Abstract

Objective:Dynamic imaging of small intestinal motility is an increasingly common research method to examine bowel physiology in health and disease. However, limited data exist to guide imaging protocols with respect to quantitative analysis. The purpose of this study is to define the required temporal resolution and scan duration in dynamic MRI for small bowel motility assessment.Methods:Six healthy volunteers underwent motility imaging with MR enterography using breath-hold protocol. A coronal two-dimensional balanced fast field echo sequence was used to acquire dynamic data at a high temporal resolution of 10 frames per second (fps). Motility was quantified by generating a registration-derived motility index for local and global regions of bowel. To evaluate temporal resolution and scan duration, the data were undersampled and the scan length was varied to determine the impact on motility index.Results:The mean motility index stabilizes at a temporal resolution of 1 fps (median absolute percentage change 1.4% for global and 1.9% for local regions of interest). The mean motility index appears to stabilize for scan durations of 15 s or more in breath-hold (median absolute % change 2.8% for global and 1.7% for local regions of interest).Conclusion:A temporal resolution of at least 1 fps and a scan duration of at least 15 s is necessary in breath-hold scans for consistent motility observations. The majority of small bowel motility studies to date are in line with these requirements.Advances in knowledge:This study suggests the minimum temporal resolution and scan duration required in breath-hold scans to obtain robust measurements of small bowel motility from MRI.

Highlights

Intestinal motility is an essential physiological process that moves food through the gut
No adverse effects were observed in the six healthy volunteers [3 females, median age 22] The acquisition resulted in breath-holds ranging from 15 to 21 s depending on the subjects ability to hold their breath, see the supplementary video 1 for a resulting breath-hold dynamic MRI
(1) By triplicating the breath-hold data set and registering and recalculating the global regions of interest (ROIs), we evaluated the registration algorithm as a potential source of the rising mean motility index

Summary

Introduction

Intestinal motility is an essential physiological process that moves food through the gut. Most of the research into bowel motility quantification using MRI has made assumptions regarding acquisition protocols. These assumptions concern (1) temporal resolution of image capture and (2) duration of acquisition, neither of which has been rigorously tested. Many researchers acquire motion capture sequences at 1 image s-1, typically over a breath-hold of ± 20 s, yet the rationale for this has not been firmly established. With respect to temporal resolution, the literature suggests that the small bowel undergoes between 9 and 12 contractions per minute, and this so called slow wave activity is described to be continuous and regular in the fasted state.[18] Menys et al[12] using 20 s breath-hold dynamic MRI data showed regions of bowel that were almost static even in healthy subjects. It is assumed that acquiring images at 1 image s-1 is sufficient to resolve small bowel contractions, the implications of inadvertently undersampling contractions are significant, and again this assumption has yet to be formally established

Methods

Results

Conclusion