title: CT Perfusion in Acute Stroke Predicts Final Infarct Volume- Inter-observer Study.
abstract: BACKGROUND
  Computed tomography perfusion (CTP) is increasingly being used in the setting of acute ischemic stroke (AIS). The aim of the current study was to compare the prognostic utility of, and inter-observer variation between, baseline appearances on non-contrast CT (using Alberta Stroke Program Early CT score(ASPECTS)) and on CTP for predicting final infarct volume. We also assessed impact of training on interpretation of these images.
  
  
  METHODS
  Retrospectively, plain head computed tomography (CT) and CTP images at presentation and CT or diffusion imaging on follow up of patients with AIS were analyzed. The lesion volume on different CTP parameters was then correlated with the final infarct volume. This analysis was done by a Neuroradiologist, a stroke Neurologist and a medical student. Kappa statistics and Intra-class correlation coefficients were used for agreement between readers. Pearson correlation coefficients were used.
  
  
  RESULTS
  Thirty eight patients with AIS met all inclusion criteria. There was very good agreement among all readers for the CTP parameters. There was only fair agreement for ASPECT score. Correlation coefficient (r-square) between CTP parameters and final infarct volume showed that cerebral blood volume was the best parameter to predict the final infarct volume followed by cerebral blood flow and time to peak. The best reader to predict the final infarct volume on the initial CT perfusion study was the neuroradiologist followed by medical student and stroke neurologist.
  
  
  CONCLUSIONS
  Cerebral blood volume defect correlated the best with the final infarct volume. There was a very good inter-observer agreement for all the CTP maps in predicting the final infarct volume despite the wide variation in the experience of the readers.
authors.affiliation: 1Department of Diagnostic Imaging,Dalhousie University.
authors.forename: Jai Jai Shiva
authors.initials: JJ
authors.lastname: Shankar
authors.affiliation: 4University of Aberdeen,Aberdeen,Scotland.
authors.forename: Gavin
authors.initials: G
authors.lastname: Langlands
authors.affiliation: 3Research Methods Unit,Capital District Health Authority,Halifax.
authors.forename: Steve
authors.initials: S
authors.lastname: Doucette
authors.affiliation: 2Division of Neuroradiology,Department of Medicine,Dalhousie University.
authors.forename: Stephen
authors.initials: S
authors.lastname: Phillips
mesh_terms: D000368:Aged; D020520:Brain Infarction / Q000000981:diagnostic imaging; D002545:Brain Ischemia / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000592:standards*; D011379:Prognosis; D020521:Stroke / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000592:standards*
keywords: Acute Ischemic Stroke; CT perfusion; Cerebral Blood Volume; Neurology- Adult; Neurology- Clinical; Neuroradiology; Neuroradiology stroke; stroke imaging