Stroke penumbra defined by an MRI-based oxygen challenge technique : 2. Validation based on the consequences of reperfusion

Robertson, Craig A and McCabe, Christopher and Gallagher, Lindsay and Lopez-Gonzalez, Maria del Rosario and Holmes, William M and Condon, Barrie and Muir, Keith W and Santosh, Celestine and Macrae, I Mhairi (2011) Stroke penumbra defined by an MRI-based oxygen challenge technique : 2. Validation based on the consequences of reperfusion. Journal of Cerebral Blood Flow and Metabolism, 31 (8). pp. 1788-1798. ISSN 0271-678X

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Abstract

Magnetic resonance imaging (MRI) with oxygen challenge (T(2)(*) OC) uses oxygen as a metabolic biotracer to define penumbral tissue based on CMRO(2) and oxygen extraction fraction. Penumbra displays a greater T(2)(*) signal change during OC than surrounding tissue. Since timely restoration of cerebral blood flow (CBF) should salvage penumbra, T(2)(*) OC was tested by examining the consequences of reperfusion on T(2)(*) OC-defined penumbra. Transient ischemia (109 ± 20 minutes) was induced in male Sprague-Dawley rats (n=8). Penumbra was identified on T(2)(*)-weighted MRI during OC. Ischemia and ischemic injury were identified on CBF and apparent diffusion coefficient maps, respectively. Reperfusion was induced and scans repeated. T(2) for final infarct and T(2)(*) OC were run on day 7. T(2)(*) signal increase to OC was 3.4% in contralateral cortex and caudate nucleus and was unaffected by reperfusion. In OC-defined penumbra, T(2)(*) signal increased by 8.4% ± 4.1% during ischemia and returned to 3.25% ± 0.8% following reperfusion. Ischemic core T(2)(*) signal increase was 0.39% ± 0.47% during ischemia and 0.84% ± 1.8% on reperfusion. Penumbral CBF increased from 41.94 ± 13 to 116.5 ± 25 mL per 100 g per minute on reperfusion. On day 7, OC-defined penumbra gave a normal OC response and was located outside the infarct. T(2)(*) OC-defined penumbra recovered when CBF was restored, providing further validation of the utility of T(2)(*) OC for acute stroke management.

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