title: Reliability of visual assessment of non-contrast CT, CT angiography source images and CT perfusion in patients with suspected ischemic stroke.
abstract: OBJECTIVE
  Good reliability of methods to assess the extent of ischemia in acute stroke is important for implementation in clinical practice, especially between observers with varying experience. Our aim was to determine inter- and intra-observer reliability of the 1/3 middle cerebral artery (MCA) rule and the Alberta Stroke Program Early CT Score (ASPECTS) for different CT modalities in patients suspected of acute ischemic stroke.
  
  
  METHODS
  We prospectively included 105 patients with acute neurological deficit due to suspected acute ischemic stroke within 9 hours after symptom onset. All patients underwent non-contrast CT, CT perfusion and CT angiography on admission. All images were evaluated twice for presence of ischemia, ischemia with >1/3 MCA involvement, and ASPECTS. Four observers evaluated twenty scans twice for intra-observer agreement. We used kappa statistics and intraclass correlation coefficient to calculate agreement.
  
  
  RESULTS
  Inter-observer agreement for the 1/3 MCA rule and ASPECTS was fair to good for non-contrast CT, poor to good for CT angiography source images, but excellent for all CT perfusion maps (cerebral blood volume, mean transit time, and predicted penumbra and infarct maps). Intra-observer agreement for the 1/3 MCA rule and ASPECTS was poor to good for non-contrast CT, fair to moderate for CT angiography source images, and good to excellent for all CT perfusion maps.
  
  
  CONCLUSIONS
  Between observers with a different level of experience, agreement on the radiological diagnosis of cerebral ischemia is much better for CT perfusion than for non-contrast CT and CT angiography source images, and therefore CT perfusion is a very reliable addition to standard stroke imaging.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Tom
authors.initials: T
authors.lastname: van Seeters
authors.forename: Geert Jan
authors.initials: GJ
authors.lastname: Biessels
authors.forename: Joris M
authors.initials: JM
authors.lastname: Niesten
authors.forename: Irene C
authors.initials: IC
authors.lastname: van der Schaaf
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Dankbaar
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Horsch
authors.forename: Willem P T M
authors.initials: WP
authors.lastname: Mali
authors.forename: L Jaap
authors.initials: LJ
authors.lastname: Kappelle
authors.forename: Yolanda
authors.initials: Y
authors.lastname: van der Graaf
authors.forename: Birgitta K
authors.initials: BK
authors.lastname: Velthuis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging*; D002545:Brain Ischemia / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D020521:Stroke / Q000000981:diagnostic imaging*