In vivo magnetic resonance evaluation of blood oxygen saturation in the superior mesenteric vein as a measure of the degree of acute flow reduction in the superior mesenteric artery: findings in a canine model.

Rationale and Objectives: The authors tested the hypothesis that changes in oxygen saturation (%HbO2) in the superior mesenteric vein (SMV), as measured with in vivo magnetic resonance (MR) oximetry, correlate with the degree of acute superior mesenteric artery (SMA) flow reduction.
Methods: Ten mongrel dogs were studied. A catheter was inserted into the SMV, and a perivascular ultrasonic flow probe and an adjustable mechanical occluder were placed around the SMA. MR oximetry was carried out at the resting state and after the SMA was constricted to predetermined levels (0%-75% of initial flow). In seven dogs, SMV blood samples were obtained immediately before and after each MR measurement; %HbO2 was measured simultaneously by using an oximeter. With linear regression analysis, the SMV %HbO2 measurements obtained at MR imaging were compared with those obtained at oximetry. With a logistic model, MR imaging changes in SMV %HbO2 were compared with the degree of SMA flow reduction.
Results: SMV %HbO2 measurements obtained with MR imaging correlated well with those obtained with oximetry (r = .97). Changes in SMV %HbO2 measured at MR imaging also correlated well with the degree of SMA flow reduction, as determined with a logistic model (P = .01).
Conclusion: Noninvasive in vivo MR measurements of SMV %HbO2 can be used to determine the degree of acute SMA flow reduction with a high degree of accuracy in a canine model.