DIFFUSION NUCLEAR-MAGNETIC-RESONANCE IMAGING IN EXPERIMENTAL STROKE -CORRELATION WITH CEREBRAL METABOLITES

Background and Purpose Diffusion-weighted nuclear magnetic resonance i maging has been shown to detect early ischemia-related alterations in experimental stroke. This raises the question of whether the observed increase in signal intensity is correlated with changes in cerebral me tabolism. After middle cerebral artery occlusion, nuclear magnetic res onance diffusion images were recorded and compared with the regional c oncentration of cerebral metabolites and with histology of identical p lanes. Methods Seven anesthetized Fischer rats were subjected to perma nent occlusion of the middle cerebral artery. T-1, T-2, and diffusion images (b factors ranging from 0 to 1500 s/mm(2)) were measured in thr ee to five planes after 7 hours. Thereafter, brains were frozen in sit u for histology and quantitative bioluminescence imaging of ATP, gluco se, lactate, and for fluorescence imaging of tissue pH. Results Seven hours after middle cerebral artery occlusion, the apparent diffusion c oefficient was reduced from 615+/-97x10(-6).mm(2).s(-1) (contralateral brain) to 359+/-42x 10(-6).mm(2).s(-1) (ischemic brain; mean+/-SD, P< .01). A precise topical coincidence was demonstrated between changes i n nuclear magnetic resonance diffusion images, pattern of histological damage, ATP-depleted areas, and local tissue acidosis, the lesion are a amounting to between 24.1% and 27.6% of the hemisphere at the level of the caudate-putamen. The area of elevated brain lactate clearly exc eeded the acidic core of the infarct and included the slightly alkalin e border zone. Conclusions The data demonstrate that after 7-hour midd le cerebral artery occlusion, the reduction of the apparent diffusion coefficient in nuclear magnetic resonance diffusion images reflects pr ecisely the region of histological injury, breakdown of energy metabol ism, and tissue acidosis.