Magnetic resonance imaging of regional cerebral blood oxygenation changes under acetazolamide in carotid occlusive disease.
BACKGROUND
Gradient-echo magnetic resonance imaging can demonstrate changes in cerebral blood oxygenation with high spatiotemporal resolution. We have previously shown that this technique allows monitoring of autoregulatory responses under vasodilatory stress in the healthy human brain. Here the approach has been extended to assess impairment of the autoregulatory reserve capacity in patients with carotid occlusive disease.


METHODS
We studied four patients with unilateral occlusion of the internal carotid artery on a 2.0-T clinical high-field magnetic resonance system. Oxygenation-sensitive imaging was based on long-echo-time, gradient-echo sequences (repetition time, 62.5 milliseconds; echo time, 30 milliseconds) with low flip angles (10 degrees) to emphasize changes in blood oxygenation rather than flow velocity. Dynamic recording monitored signal intensities before and after injecting 1 g of acetazolamide. In sections covering the hand area of the primary sensorimotor cortex, acetazolamide-induced magnetic resonance signal increases were attenuated in the vascular territories of occluded arteries. Lateralization of responses in the left and right hemispheric parts of the section corresponded to decreased hemodynamic reserve capacity as measured globally by transcranial Doppler ultrasonography.


CONCLUSIONS
The present findings indicate that magnetic resonance imaging can demonstrate exhaustion of the autoregulatory reserve capacity when monitoring cerebral blood oxygenation changes during vasodilatory stress. We suggest that this method can help to evaluate regional cerebral hemodynamics in patients with carotid occlusive disease.
Biomedizinische NMR Forschungs GmbH, Heinrich-Heine-Universität, Düsseldorf, Germany.
A
A
Kleinschmidt
H
H
Steinmetz
M
M
Sitzer
K D
KD
Merboldt
J
J
Frahm
D000086:Acetazolamide / Q000494:pharmacology; D000328:Adult; D000368:Aged; D016893:Carotid Stenosis / Q000473:pathology*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D006706:Homeostasis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D013312:Stress, Physiological / Q000503:physiopathology; D017585:Ultrasonography, Doppler, Transcranial; D014664:Vasodilation / Q000187:drug effects; D014666:Vasomotor System / Q000187:drug effects
D000086:Acetazolamide