Diffusion- and T2-weighted MR Imagings of Cerebral Infarction in Rabbit: Time Course of Imaging Findings and Histologic Correlation

ABSTRACT

PURPOSE: To correlate the serial findings obtained by diffusion- and T2-weighted imaging with histologicfind-ings obtained from 30 minutes to 31 days after the development of cerebral infarction in rabbits. MATERIALS AND METHODS: Nineteen male New Zealand white rabbits were subjected to intracerebral embolic infarction.Diffusion- and T2-weighted imagings were performed at 30 min, 2, 4 and 6 hours, and 1, 3, 5, 7, 11, 21 and 31days. Apparent diffusion coefficient (ADC) ratios and T2 signal intensity ratios of infarcted and normal brainwere calculated. Microphotographic or electron microscopic (EM) examinations were performed during hyperacute,acute and chronic infarctions. RESULTS: During hyperacute infarction, diffusion-weighted images showed highsignal intensity in the infarcted area, and ADC ratios ranged from 0.81 to 0.56. High signal intensity ondiffusion-weighted images continued until day 3, decreasing thereafter. The ADC ratio increased continuouslyafter day 1. High signal intensity on T2-weighted images was noted from 6 hours and continued until day 7,decreasing thereafter. Microphotographic findings at 6 hours were normal, but EM examination revealed cellularswelling with intact basement membrane, suggesting cytotoxic edema. During acute infarction, abnormal dilatationof the perineural space, cell destruction, and loosening of the neuropil matrix were revealed bymicrophotography. During chronic infarction, microphotographic and EM findings revealed liquefaction necrosis. CONCLUSION: These data indicate that in cases of hyperacute infarction, diffusion-weighted images reflectcy-totoxic edema more accurately than do T2-weighted images. A gradually increasing ADC ratio during the course ofinfarction may be associated with vasogenic edema and cell lysis.