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Reversible focal ischemic injury demonstrated by diffusion-weighted magnetic resonance imaging in rats
1Department of Neurology, University of Massachusetts Medical School, Worcester.
Background And Purpose:
Diffusion-weighted magnetic resonance imaging (DWI) can quantitatively display focal brain abnormalities within minutes after the onset of ischemia. We performed the present study to determine the effects of 1 and 2 hours of temporary ischemia on DWI.
Methods:
We examined DWI and T2-weighted magnetic resonance images (T2WI) during and after 1 and 2 hours of temporary middle cerebral artery occlusion in rats (n = 10 for each group). In a subgroup of four animals from each group, we employed perfusion magnetic resonance imaging to monitor cerebral perfusion. Neurological outcome and infarct size after survival for 24 hours were compared between the groups and correlated with DWI and T2WI studies.
Results:
Perfusion studies qualitatively documented hypoperfusion and reperfusion during and after temporary occlusion. Lesion size on DWI during reperfusion was significantly less than that during ischemia for 1 (55% decline, p less than 0.02) but not 2 hours of occlusion. The DWI signal intensity ratio (intensity compared with that in the contralateral homologous area) just before withdrawal of the occluder was significantly less in regions where the hyperintensity disappeared after withdrawal than in regions with persistent hyperintensity (p less than 0.002). The T2WI studies revealed few or no abnormalities, except after 2 hours of occlusion. The neurological outcome was significantly better in the 1-hour than in the 2-hour group (p less than 0.05). Postmortem infarct volume was significantly smaller in the 1-hour group than in the 2-hour group (p less than 0.05). The postwithdrawal DWI accurately predicted infarct size (R = 0.96, p less than 0.0001).
Conclusions:
The present study indicates that DWI can rapidly display not only irreversible but also reversible ischemic brain damage and enhances the importance of DWI as a diagnostic modality for stroke.
Insights
Diffusion-weighted imaging (DWI) detects reversible and irreversible ischemic brain damage quickly. This study shows DWI accurately predicts infarct size, highlighting its diagnostic value for stroke.
Area of Science:
- Neuroimaging
- Cerebrovascular Diseases
- Experimental Neurology
Background:
- Diffusion-weighted imaging (DWI) offers rapid quantitative assessment of focal brain abnormalities post-ischemia.
- Understanding the impact of ischemia duration on DWI findings is crucial for stroke diagnosis.
Purpose of the Study:
- To evaluate the effects of 1-hour and 2-hour temporary ischemia on Diffusion-weighted imaging (DWI) findings.
- To correlate DWI and T2-weighted imaging (T2WI) with neurological outcomes and infarct size.
Main Methods:
- Middle cerebral artery occlusion was induced in rats for 1 or 2 hours.
- Diffusion-weighted imaging (DWI), T2-weighted imaging (T2WI), and perfusion MRI were performed.
- Neurological deficits and infarct volumes were assessed post-survival.
Main Results:
- DWI showed significantly reduced lesion size during reperfusion after 1-hour, but not 2-hour, occlusion.
- T2WI revealed minimal abnormalities except after 2-hour occlusion.
- One-hour occlusion resulted in better neurological outcomes and smaller infarcts compared to 2-hour occlusion.
- Post-occlusion DWI accurately predicted final infarct size (R = 0.96).
Conclusions:
- Diffusion-weighted imaging (DWI) effectively identifies both reversible and irreversible ischemic brain damage.
- DWI's ability to predict infarct size enhances its importance as a diagnostic tool for acute stroke.