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

OBJECTIVE Dynamic imaging of small intestinal motility is an increasingly common research method to examine bowel physiology in health and disease. However, limited data exists 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 6 healthy volunteers underwent motility imaging with MR enterography using breath-hold protocol. A coronal 2D bFFE sequence was used to acquire dynamic data at high temporal resolution of 10fps. 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 was 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 1fps (median absolute percentage change 1.4% for global and 1.9% for local ROIs). The mean motility index appears to stabilize for scan durations of 15s. or more in breath-hold (median absolute % change 2.8% for global and 1.7% for local ROIs). CONCLUSION A temporal resolution of at least 1 fps and a scan duration of at least 15 seconds 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.