title: Stroke penumbra defined by an MRI-based oxygen challenge technique: 2. Validation based on the consequences of reperfusion.
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.
authors.affiliation: Glasgow Experimental MRI Centre, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK. c.robertson.1@research.gla.ac.uk
authors.forename: Craig A
authors.initials: CA
authors.lastname: Robertson
authors.forename: Christopher
authors.initials: C
authors.lastname: McCabe
authors.forename: Lindsay
authors.initials: L
authors.lastname: Gallagher
authors.forename: Maria del Rosario
authors.initials: Mdel R
authors.lastname: Lopez-Gonzalez
authors.forename: William M
authors.initials: WM
authors.lastname: Holmes
authors.forename: Barrie
authors.initials: B
authors.lastname: Condon
authors.forename: Keith W
authors.initials: KW
authors.lastname: Muir
authors.forename: Celestine
authors.initials: C
authors.lastname: Santosh
authors.forename: I Mhairi
authors.initials: IM
authors.lastname: Macrae
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D002546:Ischemic Attack, Transient / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D020521:Stroke / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology
chemical_list: D010100:Oxygen