title: Early stroke detection and extent: impact of experience and the role of computed tomography angiography source images.
abstract: OBJECTIVE
  To test the performance of computed tomography angiography "source images" (CTA-SI) versus unenhanced CT (NCCT) for stroke detection and extent using the Alberta Stroke Programme Early CT Score (ASPECTS), and examine the effect of experience and clinical history.
  
  
  METHODS
  Studies of 23 consecutive patients presenting within 4.5h were analysed by three reviewers of varying experience. Each reviewer, blinded to clinical information reviewed a random order of NCCT and CTA-SI and documented side of infarct and the ASPECTS. The readings were repeated for CTA-SI with and without clinical information. Performance measures and observer agreement were calculated. Applying an ASPECTS threshold of<or=7, the number of patients misclassified was determined.
  
  
  RESULTS
  CTA-SI improved trainee accuracy by 9%, but had little impact on more experienced readers. The accuracy and sensitivity of stroke extent assessment was increased for all readers, but was greatest for the trainee (17% and 12%, respectively). Clinical history contributed little to CTA-SI accuracy. Observer agreement was higher for CTA-SI. NCCT could have resulted in the misclassification of more patients than CTA-SI.
  
  
  CONCLUSIONS
  CTA-SI are an important adjunct in acute stroke assessment, improving stroke extent determination for all readers irrespective of level of experience. In addition less experienced readers may benefit from CTA-SI for detection of presence of strokes. CTA-SI performance appears independent of clinical history. CTA-SI resulted in fewer misclassified patients if an ASPECTS threshold of <or=7 is considered.
authors.affiliation: Department of Neuroradiology, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Canada. richardaviv@lineone.net <richardaviv@lineone.net>
authors.forename: R I
authors.initials: RI
authors.lastname: Aviv
authors.forename: I
authors.initials: I
authors.lastname: Shelef
authors.forename: S
authors.initials: S
authors.lastname: Malam
authors.forename: S
authors.initials: S
authors.lastname: Chakraborty
authors.forename: D J
authors.initials: DJ
authors.lastname: Sahlas
authors.forename: G
authors.initials: G
authors.lastname: Tomlinson
authors.forename: S
authors.initials: S
authors.lastname: Symons
authors.forename: A J
authors.initials: AJ
authors.lastname: Fox
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002533:Cerebral Angiography / Q000379:methods*; D002983:Clinical Competence; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011379:Prognosis; D012680:Sensitivity and Specificity; D020521:Stroke / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*