Early stroke detection and extent: impact of experience and the role of computed tomography angiography source images

Clin Radiol. 2007 May;62(5):447-52. doi: 10.1016/j.crad.2006.11.019. Epub 2007 Mar 21.


Aim: 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.

Materials and 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.

Conclusion: 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.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Cerebral Angiography / methods*
  • Clinical Competence
  • Early Diagnosis
  • Female
  • Humans
  • Male
  • Middle Aged
  • Observer Variation
  • Prognosis
  • Sensitivity and Specificity
  • Stroke / diagnostic imaging*
  • Tomography, X-Ray Computed / methods*