DISSOCIATION BETWEEN LACTATE ACCUMULATION AND ACIDOSIS IN MIDDLE CEREBRAL ARTERY-OCCLUDED RATS ASSESSED BY P-31 AND H-1-NMR METABOLIC IMAGES UNDER A 2-T MAGNETIC-FIELD

The relationships among tissue edema, lactate accumulation, and intrac ellular pH in middle cerebral artery (MCA)-occluded rats were investig ated with multiecho H-1 magnetic resonance imaging and spatially resol ved metabolic images constructed by H-1 and P-31 nuclear magnetic reso nance (NMR) chemical shift imaging (CSI), For the effective and sensit ive detection of NMR signals from the brain, outer volume suppression (OVS), reduced k-space sampling and proton irradiation were incorporat ed into the CSI sequences, The consecutive three measurements of calcu lated T-2 image, lactate image, and pH image which were required for 3 .75 h were repeated for four cycles of 1-16 h after MCA occlusion, Tis sue edema and lactate accumulation in the infarcted region were gradua lly and consistently increased during the 15-h observation period, In contrast, severe acidosis was already detected on the first pH image ( 2-4.7 h after MCA occlusion); thereafter, the degree of acidosis becam e milder and showed no further progression. The dissociation between t he time courses of the lactate accumulation and pH decrease was clearl y demonstrated by the NMR metabolic images, Acid-base balance in cereb ral infarction might be affected not only by lactate production but al so by complicated interactions with tissue edema and some other factor s. Copyright (C) 1996 Elsevier Science Inc.