Feasibility of small bowel flow rate measurement with MRI

OBJECTIVE: To evaluate whether it is feasible to measure the segmental flux of small bowel content using MR phase-contrast (PC) pulse sequences. MATERIALS AND METHODS: Using a phantom the accuracy of flux measurements was validated. Afterwards, 10 volunteers were included in a prospective clinical trial. To provide standardized small bowel distension, all volunteers ingested four equal portions of 400 mL of water doped with 5 mL gadoterate and 5.8 g Metamucil mite. The MR protocol covering the sagittal cross-sections of the small bowel included several two-dimensional (2D) PC sequences with a velocity encoding of 7 cm/second at a temporal resolution of 0.55 second. As proof of concept time-dependent flux was measured after intravenous (i.v.) administration of a spasmolytic agent in one volunteer. RESULTS: Phantom measurements resulted in an excellent correlation between pump and PC measured flow rates (R = 0.999). Time-resolved small bowel flux was successfully measured in distended small bowel loops of all volunteers. A mean flow rate of 0.188 mL/second (standard deviation +/- 0.144 mL/second) was documented. The flux plots presented a sinus wave-like shape with regular aboral and oral flow. A spasmolytic effect both on flux and motility could be shown with residual flux despite complete arrest of small bowel motility. CONCLUSION: PC MRI allows time-resolved in vivo measurement of small bowel flux in single well-distended bowel loops filled with gadolinium-doped aqueous solution.