Correlation of sequential MR images of microsphere-induced cerebral ischemia with histologic changes in rats.
OBJECTIVE
To determine the time course of changes in MRI findings of multiple cerebral microembolism, the authors induced experimental multiple microinfarctions in rats using microspheres and then examined sequential MRI and histopathologic findings. The authors also evaluated how the amount of injected embolic materials affected the findings.


METHODS
The authors injected 25-microm microspheres (range, 2000-8000 gm) into the unilateral internal carotid arteries of rats. The animals were assessed by MRI and histopathology at 1 day or 8 days after embolization.


RESULTS
One day after embolization, multiple high-intensity areas on T2-weighted images were related to the number of injected microspheres and were associated with regions of cerebral edema on histopathologic specimens. On day 8, the high-intensity areas on T2-weighted images observed on day 1 were markedly diminished in the groups receiving up to 6000 microspheres. In the group injected with 8000 microspheres, however, the high-intensity areas were less diminished, and these areas were significantly larger than in the other groups (P < 0.05).


CONCLUSIONS
The MRI features of cerebral ischemia or infarction induced by microsphere embolism vary depending on the number of injected microspheres. Recovery from acute cerebral embolism has a threshold based on ischemic cell volume.
Fukuchi
K
K
Division of Tracer Kinetics, Biomedical Research Center, Osaka University Medical School, Suita, Japan.
Kusuoka
H
H
Watanabe
Y
Y
Nishimura
T
T
D000704:Analysis of Variance; D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000473:pathology; D002545:Brain Ischemia / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D002244:Carbon; D020766:Intracranial Embolism / Q000175:diagnosis / Q000209:etiology / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D008297:Male; D008863:Microspheres; D015588:Observer Variation; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D002244:Carbon