title: Perfusion computed tomography thresholds defining ischemic penumbra and infarct core: studies in a rat stroke model.
abstract: BACKGROUND
  Perfusion computed tomography is becoming more widely used as a clinical imaging tool to predict potentially salvageable tissue (ischemic penumbra) after ischemic stroke and guide reperfusion therapies.
  
  
  OBJECTIVE
  The study aims to determine whether there are important changes in perfusion computed tomography thresholds defining ischemic penumbra and infarct core over time following stroke.
  
  
  METHODS
  Permanent middle cerebral artery occlusion was performed in adult outbred Wistar rats (n = 6) and serial perfusion computed tomography scans were taken every 30 mins for 2 h. To define infarction thresholds at 1 h and 2 h post-stroke, separate groups of rats underwent 1 h (n = 6) and 2 h (n = 6) of middle cerebral artery occlusion followed by reperfusion. Infarct volumes were defined by histology at 24 h. Co-registration with perfusion computed tomography maps (cerebral blood flow, cerebral blood volume, and mean transit time) permitted pixel-based analysis of thresholds defining infarction, using receiver operating characteristic curves.
  
  
  RESULTS
  Relative cerebral blood flow was the perfusion computed tomography parameter that most accurately predicted penumbra (area under the curve = 0.698) and also infarct core (area under the curve = 0.750). A relative cerebral blood flow threshold of < 75% of mean contralateral cerebral blood flow most accurately predicted penumbral tissue at 0.5 h (area under the curve = 0.660), 1 h (area under the curve = 0.659), 1.5 h (area under the curve = 0.636), and 2 h (area under the curve = 0.664) after stroke onset. A relative cerebral blood flow threshold of < 55% of mean contralateral most accurately predicted infarct core at 1 h (area under the curve = 0.765) and at 2 h (area under the curve = 0.689) after middle cerebral artery occlusion.
  
  
  CONCLUSIONS
  The data provide perfusion computed tomography defined relative cerebral blood flow thresholds for infarct core and ischemic penumbra within the first two hours after experimental stroke in rats. These thresholds were shown to be stable to define the volume of infarct core and penumbra within this time window.
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: D D
authors.initials: DD
authors.lastname: McLeod
authors.affiliation: Department of Neurology, John Hunter Hospital, Hunter Region M.C., New South Wales, Australia.
authors.forename: M W
authors.initials: MW
authors.lastname: Parsons
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Hood
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: B
authors.initials: B
authors.lastname: Hiles
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Allen
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: S K
authors.initials: SK
authors.lastname: McCann
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Murtha
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: M B
authors.initials: MB
authors.lastname: Calford
authors.affiliation: Department of Neurology, John Hunter Hospital, Hunter Region M.C., New South Wales, Australia.
authors.forename: C R
authors.initials: CR
authors.lastname: Levi
authors.affiliation: Discipline of Human Physiology, School of Biomedical Sciences & Pharmacy, Faculty of Health, Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales, Australia.|Department of Neurology, John Hunter Hospital, Hunter Region M.C., New South Wales, Australia.
authors.forename: N J
authors.initials: NJ
authors.lastname: Spratt
mesh_terms: D000818:Animals; D021461:Animals, Outbred Strains; D001921:Brain / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D004195:Disease Models, Animal; D020244:Infarction, Middle Cerebral Artery; D055420:Perfusion Imaging / Q000379:methods*; D012372:ROC Curve; D017208:Rats, Wistar; D020521:Stroke; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: infarct core; ischemic penumbra; perfusion computed tomography