MRI-based pre- and postprandial flow in the mesenteric vasculature of patients with suspected chronic mesenteric ischemia.

PURPOSE: The physiological increase of mesenteric blood flow after a meal is impaired in patients with occlusive chronic mesenteric ischemia (CMI). This principle could be used to develop a highly desired diagnostic test assessing the sufficiency of the collateral mesenteric circulation. This study assesses the potential to identify CMI patients using two-dimensional time-resolved phase-contrast magnetic resonance imaging (2D PC-MRI) flow measurements. METHOD: This prospective cohort study included patients with suspected CMI, based on: typical history, imaging, and functional testing. Cardiac gated 2D PC-MRI flow measurements (expressed as ml/min/kg) were performed in mesenteric arteries and veins during inspiration and expiration, after six hours of fasting and 20, 30, and 40 min after a meal challenge with a high caloric drink. RESULTS: Flow measurements were obtained in 19 patients: 8 CMI and 11 non-CMI. CMI patients showed a significantly smaller increase in postprandial blood flow in the superior mesenteric artery (SMA) at 30 and 40 min (30 min CMI 1.27(0.12-2.44) vs. non-CMI 7.82(6.28-10.90); 40 min CMI 0.30(-0.26-3.16) vs. non-CMI 7.94(6.32-10.90)) and a lower total arterial flow at 40 min (CMI 3.21(-0.72-5.05) vs. non-CMI 9.31(5.58-13.83)). Repeated flow measurements showed normalization of impaired postprandial venous flow after mesenteric artery stenting in one patient. CONCLUSIONS: The significantly lower increase in postprandial mesenteric blood flow in CMI patients confirms the promise of mesenteric blood flow measurements, before and 30-40 min after a meal, as a future diagnostic test to identify CMI patients among patients with a high clinical suspicion of CMI and mesenteric artery stenosis.

Cloud-processed 4D CMR flow imaging for pulmonary flow quantification.

OBJECTIVES: In this study, we evaluated a cloud-based platform for cardiac magnetic resonance (CMR) four-dimensional (4D) flow imaging, with fully integrated correction for eddy currents, Maxwell phase effects, and gradient field non-linearity, to quantify forward flow, regurgitation, and peak systolic velocity over the pulmonary artery. METHODS: We prospectively recruited 52 adult patients during one-year period from July 2014. The 4D flow and planar (2D) phase-contrast (PC) were acquired during same scanning session, but 4D flow was scanned after injection of a gadolinium-based contrast agent. Eddy-currents were semi-automatically corrected using the web-based software. Flow over pulmonary valve was measured and the 4D flow values were compared against the 2D PC ones. RESULTS: The mean forward flow was 92 (±30) ml/cycle measured with 4D flow and 86 (±29) ml/cycle measured with 2D PC, with a correlation of 0.82 and a mean difference of -6ml/cycle (-41-29). For the regurgitant fraction the correlation was 0.85 with a mean difference of -0.95% (-17-15). Mean peak systolic velocity measured with 4D flow was 92 (±49) cm/s and 108 (±56) cm/s with 2D PC, having a correlation of 0.93 and a mean difference of 16cm/s (-24-55). CONCLUSION: 4D flow imaging post-processed with an integrated cloud-based application accurately quantifies pulmonary flow. However, it may underestimate the peak systolic velocity.