title: Influence of 100% and 40% oxygen on penumbral blood flow, oxygen level, and T2*-weighted MRI in a rat stroke model.
abstract: Accurate imaging of the ischemic penumbra is a prerequisite for acute clinical stroke research. T(2)(*) magnetic resonance imaging (MRI) combined with an oxygen challenge (OC) is being developed to detect penumbra based on changes in blood deoxyhemoglobin. However, inducing OC with 100% O(2) induces sinus artefacts on human scans and influences cerebral blood flow (CBF), which can affect T(2)(*) signal. Therefore, we investigated replacing 100% O(2) OC with 40% O(2) OC (5 minutes 40% O(2) versus 100% O(2)) and determined the effects on blood pressure (BP), CBF, tissue pO(2), and T(2)(*) signal change in presumed penumbra in a rat stroke model. Probes implanted into penumbra and contralateral cortex simultaneously recorded pO(2) and CBF during 40% O(2) (n=6) or 100% O(2) (n=8) OC. In a separate MRI study, T(2)(*) signal change to 40% O(2) (n=6) and 100% O(2) (n=5) OC was compared. Oxygen challenge (40% and 100% O(2)) increased BP by 8.2% and 18.1%, penumbra CBF by 5% and 15%, and penumbra pO(2) levels by 80% and 144%, respectively. T(2)(*) signal significantly increased by 4.56% ± 1.61% and 8.65% ± 3.66% in penumbra compared with 2.98% ± 1.56% and 2.79% ± 0.66% in contralateral cortex and 1.09% ± 0.82% and -0.32% ± 0.67% in ischemic core, respectively. For diagnostic imaging, 40% O(2) OC could provide sufficient T(2)(*) signal change to detect penumbra with limited influence in BP and CBF.
authors.affiliation: Glasgow Experimental MRI Centre, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, UK.
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Baskerville
authors.forename: Graeme A
authors.initials: GA
authors.lastname: Deuchar
authors.forename: Christopher
authors.initials: C
authors.lastname: McCabe
authors.forename: Craig A
authors.initials: CA
authors.lastname: Robertson
authors.forename: William M
authors.initials: WM
authors.lastname: Holmes
authors.forename: Celestine
authors.initials: C
authors.lastname: Santosh
authors.forename: I Mhairi
authors.initials: IM
authors.lastname: Macrae
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002560:Cerebrovascular Circulation / Q000502:physiology; D003952:Diagnostic Imaging; D004195:Disease Models, Animal; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D020521:Stroke / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology
chemical_list: D010100:Oxygen