OXYGENATION IN THE RABBIT MYOCARDIUM - ASSESSMENT WITH SUSCEPTIBILITY-DEPENDENT MR-IMAGING

PURPOSE: To determine the feasibility of using hemoglobin (Kb) desatur ation as an indicator of myocardial oxygenation. MATERIALS AND METHODS : High resolution gradient-echo nuclear magnetic resonance (MR) images of isolated, blood-perfused rabbit hearts were obtained at various bl ood oxygenation levels. The hearts were perfused at 37 degrees C with a Langendorff apparatus modified for nuclear MR imaging. The perfusate contained bovine red blood cells in a cardioplegic solution that elim inated motion artifacts and minimized arteriovenous oxygenation differ ences. Hb saturation was varied (7%-100%) randomly. Perfusion pressure was continuously monitored, and blood samples were obtained. RESULTS: There was a substantial correlation between image signal intensity in the myocardium and Hb saturation in the blood, believed to be due to susceptibility effects of the paramagnetic species deoxyhemoglobin. CO NCLUSION: Direct and noninvasive determination of regional Kb saturati on with susceptibility-dependent MR imaging may provide information re garding regional myocardial O-2 content.