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 chang es in oxygen saturation (%HbO(2)) in the superior mesenteric vein (SMV ), as measured with in vivo magnetic resonance (MR) oximetry, correlat e with the degree of acute superior mesenteric artery (SMA) flow reduc tion. Methods. Ten mongrel dogs were studied. A catheter was inserted into the SMV, and a perivascular ultrasonic flow probe and an adjustab le mechanical occluder were placed around the SMA. MR oximetry was car ried out at the resting state and after the SMA was constricted to pre determined levels (0%-75% of initial flow). In seven dogs, SMV blood s amples were obtained immediately before and after each MR measurement; %HbO, was measured simultaneously by using an oximeter. With linear r egression analysis, the SMV %HbO, measurements obtained at MR imaging were compared with those obtained at oximetry. With a logistic model, MR imaging changes in SMV %HbO, were compared with the degree of SMA f low reduction. Results. SMV %HbO(2) measurements obtained with MR imag ing correlated well with those obtained with oximetry (r = .97). Chang es in SMV %HbO(2) 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 %HbO(2) can be used to determine the degree of acute SMA flow reduction with a high degree of accuracy in a canine model.