title: Internal carotid artery stenosis: accuracy of subjective visual impression for evaluation with digital subtraction angiography and contrast-enhanced MR angiography.
abstract: OBJECTIVE
  To prospectively determine, for both digital subtraction angiography (DSA) and contrast material-enhanced magnetic resonance (MR) angiography, the accuracy of subjective visual impression (SVI) in the evaluation of internal carotid artery (ICA) stenosis, with objective caliper measurements serving as the reference standard.
  
  
  METHODS
  Local ethics committee approval and written informed patient consent were obtained. A total of 142 symptomatic patients (41 women, 101 men; mean age, 70 years; age range, 44-89 years) suspected of having ICA stenosis on the basis of Doppler ultrasonographic findings underwent both DSA and contrast-enhanced MR angiography. With each modality, three independent neuroradiologists who were blinded to other test results first visually estimated and subsequently objectively measured stenoses. Diagnostic accuracy and percentage misclassification for correct categorization of 70%-99% stenosis were calculated for SVI, with objective measurements serving as the reference standard. Interobserver variability was determined with kappa statistics.
  
  
  RESULTS
  After exclusion of arteries that were unsuitable for measurement, 180 vessels remained for analysis with DSA and 159 vessels remained for analysis with contrast-enhanced MR angiography. With respect to 70%-99% stenosis, SVI was associated with average misclassification of 8.9% for DSA (8.9%, 7.8%, and 10.0% for readers A, B, and C, respectively) and of 11.7% for contrast-enhanced MR angiography (11.3%, 8.8%, and 15.1% for readers A, B, and C, respectively). Negative predictive values were excellent (92.3%-100%). Interobserver variability was higher for SVI (DSA, kappa = 0.62-0.71; contrast-enhanced MR angiography, kappa = 0.57-0.69) than for objective measurements (DSA, kappa = 0.75-0.80; contrast-enhanced MR angiography, kappa = 0.66-0.72).
  
  
  CONCLUSIONS
  SVI alone is not recommended for evaluation of ICA stenosis with both DSA and contrast-enhanced MR angiography. SVI may be acceptable as an initial screening tool to exclude the presence of 70%-99% stenosis, but caliper measurements are warranted to confirm the presence of such stenosis.
authors.affiliation: University Department of Radiology, Addenbrooke's Hospital, Box 219, Cambridge CB2 2QQ, England.
authors.forename: Jean Marie
authors.initials: JM
authors.lastname: U-King-Im
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Graves
authors.forename: Justin J
authors.initials: JJ
authors.lastname: Cross
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Higgins
authors.forename: Josephine
authors.initials: J
authors.lastname: Wat
authors.forename: Rikin A
authors.initials: RA
authors.lastname: Trivedi
authors.forename: Tjun
authors.initials: T
authors.lastname: Tang
authors.forename: Simon P S
authors.initials: SP
authors.lastname: Howarth
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kirkpatrick
authors.forename: Nagui M
authors.initials: NM
authors.lastname: Antoun
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Gillard
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015901:Angiography, Digital Subtraction / Q000379:methods*; D002343:Carotid Artery, Internal; D016893:Carotid Stenosis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D016009:Chi-Square Distribution; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA