title: Identification of penumbra and infarct in acute ischemic stroke using computed tomography perfusion-derived blood flow and blood volume measurements.
abstract: OBJECTIVE
  We investigated whether computed tomography (CT) perfusion-derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients.
  
  
  METHODS
  Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (n=16) and those without (n=9). Penumbra was operationally defined as tissue with an admission CBF <25 mL x 100 g(-1) x min(-1) that was not infarcted on the 5- to 7-day NCCT. Logistic regression was applied to differentiate between infarct and penumbra data points.
  
  
  RESULTS
  For recanalized patients, CBF was significantly lower (P<0.05) for infarct (13.3+/-3.75 mL x 100 g(-1) x min(-1)) than penumbra (25.0+/-3.82 mL x 100 g(-1) x min(-1)). CBV in the penumbra (2.15+/-0.43 mL x 100 g(-1)) was significantly higher than contralateral (1.78+/-0.30 mL x 100 g(-1)) and infarcted tissue (1.12+/-0.37 mL x 100 g(-1)). Logistic regression using an interaction term (CBFxCBV) resulted in sensitivity, specificity, and accuracy of 97.0%, 97.2%, and 97.1%, respectively. The interaction term resulted in a significantly better (P<0.05) fit than CBF or CBV alone, suggesting that the CBV threshold for infarction varies with CBF. For patients without recanalization, CBF and CBV for infarcted regions were 15.1+/-5.67 mL x 100 g(-1) x min(-1) and 1.17+/-0.41 mL x 100 g(-1), respectively.
  
  
  CONCLUSIONS
  We have shown in a limited sample of patients that CBF and CBV obtained from CTP can be sensitive and specific for infarction and should be investigated further in a prospective trial to assess their utility for differentiating between infarct and penumbra.
authors.affiliation: University of Western Ontario, London, ON, Canada.
authors.forename: B D
authors.initials: BD
authors.lastname: Murphy
authors.forename: A J
authors.initials: AJ
authors.lastname: Fox
authors.forename: D H
authors.initials: DH
authors.lastname: Lee
authors.forename: D J
authors.initials: DJ
authors.lastname: Sahlas
authors.forename: S E
authors.initials: SE
authors.lastname: Black
authors.forename: M J
authors.initials: MJ
authors.lastname: Hogan
authors.forename: S B
authors.initials: SB
authors.lastname: Coutts
authors.forename: A M
authors.initials: AM
authors.lastname: Demchuk
authors.forename: M
authors.initials: M
authors.lastname: Goyal
authors.forename: R I
authors.initials: RI
authors.lastname: Aviv
authors.forename: S
authors.initials: S
authors.lastname: Symons
authors.forename: I B
authors.initials: IB
authors.lastname: Gulka
authors.forename: V
authors.initials: V
authors.lastname: Beletsky
authors.forename: D
authors.initials: D
authors.lastname: Pelz
authors.forename: V
authors.initials: V
authors.lastname: Hachinski
authors.forename: R
authors.initials: R
authors.lastname: Chan
authors.forename: T-Y
authors.initials: TY
authors.lastname: Lee
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D001810:Blood Volume; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002470:Cell Survival; D002533:Cerebral Angiography / Q000379:methods*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D020244:Infarction, Middle Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010477:Perfusion; D015424:Reperfusion; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*