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Pathophysiological topography of acute ischemia by combined diffusion-weighted and perfusion MRI
D G Darby1, P A Barber, R P Gerraty
1Department of Neurology, The Royal Melbourne Hospital, University of Melbourne, Australia.
Background And Purpose:
Combined echoplanar MRI diffusion-weighted imaging (DWI), perfusion imaging (PI), and magnetic resonance angiography (MRA) can be used to visualize acute brain ischemia and predict lesion evolution and functional outcome. The appearance of a larger lesion by PI than by DWI quantitatively defines a mismatch of potential clinical importance. Qualitative lesion variations exist in the topographic concordance of this mismatch. We examined both the topographic heterogeneity and relative frequency of mismatched patterns in acute stroke using these MRI techniques.
Methods:
Acute DWI, PI, and MRA studies of 34 prospectively recruited patients with supratentorial ischemic lesions scanned within 24 hours of stroke onset (range 2.5 to 23.3 hours, 12 patients <6 hours) were analyzed.
Results:
Ischemic lesions were predominantly in the middle cerebral artery (MCA) territory (94%), with DWI lesions most commonly affecting the insular region. Mismatched patterns with PI lesion larger than DWI lesion occurred in 21 patients (62% overall), in all 4 patients imaged within 3 hours, and in 44% of patients imaged after 18 hours. A patient with a large PI but no DWI lesion and severe clinical deficit at 2.5 hours after stroke onset recovered completely. Regional variations in DWI and PI lesion loci were found, inferring site of proximal MCA occlusion, embolic pathogenesis, and regional arterial reperfusion.
Conclusions:
Analysis of the topographic concordance of PI and DWI lesions in acute stroke reveals regional PI lesions without concomitant DWI lesions, which do not necessarily progress to infarction but may suggest stroke pathogenesis and site of current arterial occlusion. Location of DWI lesions may suggest an earlier site of arterial occlusion and regions of maximal perfusion deficit.
Insights
Magnetic resonance imaging (MRI) using diffusion-weighted imaging (DWI) and perfusion imaging (PI) reveals perfusion-DWI mismatch in acute stroke. This mismatch can predict lesion evolution and indicate stroke cause, aiding in treatment decisions.
Area of Science:
- Neuroimaging
- Stroke research
- Medical diagnostics
Background:
- Acute ischemic stroke diagnosis relies on advanced imaging techniques.
- Diffusion-weighted imaging (DWI) and perfusion imaging (PI) are crucial MRI modalities.
- Identifying perfusion-DWI mismatch is key for predicting stroke outcomes.
Purpose of the Study:
- To analyze the topographic heterogeneity and frequency of perfusion-DWI mismatch patterns in acute stroke.
- To investigate the clinical significance of mismatch variations in acute ischemic stroke.
- To correlate MRI findings with stroke pathogenesis and arterial occlusion sites.
Main Methods:
- Prospective analysis of 34 acute supratentorial ischemic stroke patients within 24 hours of onset.
- Utilized combined echoplanar MRI diffusion-weighted imaging (DWI), perfusion imaging (PI), and magnetic resonance angiography (MRA).
- Evaluated topographic concordance and lesion size discrepancies between DWI and PI.
Main Results:
- A perfusion lesion larger than the DWI lesion (mismatch) was observed in 62% of patients.
- Mismatch patterns were more frequent in early imaging (<3 hours) and present in 44% after 18 hours.
- Regional variations in DWI and PI lesions suggested proximal middle cerebral artery (MCA) occlusion and reperfusion.
Conclusions:
- Regional PI lesions without DWI lesions may indicate stroke pathogenesis and current arterial occlusion, not necessarily infarction.
- DWI lesion location can suggest earlier occlusion sites and maximal perfusion deficits.
- Topographic analysis of PI-DWI mismatch provides insights into acute stroke mechanisms and evolution.