EARLY MR DETECTION OF EXPERIMENTALLY-INDUCED CEREBRAL-ISCHEMIA USING MAGNETIC-SUSCEPTIBILITY CONTRAST AGENTS - COMPARISON BETWEEN GADOPENTETATE DIMEGLUMINE AND IRON-OXIDE PARTICLES

PURPOSE: To evaluate early patterns of MR changes in a rat model of ce rebral ischemia using the first pass of two magnetic susceptibility co ntrast agents. METHODS: One hour after endovascular middle cerebral ar tery occlusion, all animals were examined in an experimental MR unit. After bolus application of gadopentetate dimeglumine and, 10 minutes l ater, of iron oxide particles, the MR changes of the first pass of the se contrast agents were followed using a T2-weighted fast low-angle s hot sequence. Time-densitiy curves of both contrast agents were analyz ed and compared. RESULTS: After bolus injection of either (paramagneti c) gadopentetate dimeglumine or superparamagnetic particles, nonischem ic brain parenchyma decreased markedly in signal, whereas the ischemic brain area remained relatively hyperintense (and thus became clearly delineated). Only after application of gadopentetate dimeglumine did a mild reduction in signal occur in the ischemic hemisphere, although t he main artery was occluded. An explanation for this phenomenon might be residual capillary perfusion (plasma flow), which is detectable onl y when the smaller (paramagnetic) contrast molecules are being used. C ONCLUSIONS: Cerebral perfusion deficits can be detected 1 hour after v ascular occlusion with T2-weighted fast low-angle shot sequences and bolus injection of paramagnetic or superparamagnetic MR contrast agent s. Gadopentetate dimeglumine may be used as a marker of microcirculato ry plasma flow.