MAGNETIC-RESONANCE-IMAGING OF REGIONAL CEREBRAL BLOOD OXYGENATION CHANGES UNDER ACETAZOLAMIDE IN CAROTID OCCLUSIVE DISEASE

Background Gradient-echo magnetic resonance imaging can demonstrate ch anges in cerebral blood oxygenation with high spatiotemporal resolutio n. We have previously shown that this technique allows monitoring of a utoregulatory responses under vasodilatory stress in the healthy human brain. Here the approach has been extended to assess impairment of th e autoregulatory reserve capacity in patients with carotid occlusive d isease. Summary of Report We studied four patients with unilateral occ lusion of the internal carotid artery on a 2.0-T clinical high-field m agnetic resonance system. Oxygenation-sensitive imaging was based on l ong-echo-time, gradient-echo sequences (repetition time, 62.5 millisec onds; echo time, 30 milliseconds) with low flip angles (10 degrees) to emphasize changes in blood oxygenation rather than flow velocity. Dyn amic recording monitored signal intensities before and after injecting 1 g of acetazolamide. In sections covering the hand area of the prima ry sensorimotor cortex, acetazolamide-induced magnetic resonance signa l increases were attenuated in the vascular territories of occluded ar teries. Lateralization of responses in the left and right hemispheric parts of the section corresponded to decreased hemodynamic reserve cap acity as measured globally by transcranial Doppler ultrasonography. Co nclusions The present findings indicate that magnetic resonance imagin g can demonstrate exhaustion of the autoregulatory reserve capacity wh en monitoring cerebral blood oxygenation changes during vasodilatory s tress. We suggest that this method can help to evaluate regional cereb ral hemodynamics in patients with carotid occlusive disease.