title: Carotid stenosis index revisited with direct CT angiography measurement of carotid arteries to quantify carotid stenosis.
abstract: OBJECTIVE
  All carotid stenosis ratio methods are based on the inability of digital subtraction angiography to measure in millimeters. Each method has potential flaws. The Carotid Stenosis Index (CSI) was designed to reduce ambiguities of NASCET and ECST ratios. We test this method's ability to correctly estimate carotid stenosis using direct computed tomography angiography millimeter measures of the carotid arteries.
  
  
  METHODS
  Two neuroradiologists reviewed computed tomography angiographies of 268 carotids with atherosclerotic disease. Millimeter measurements were obtained at the narrowest diameter of the residual stenotic lumen, actual carotid bulb diameter (at level of greatest stenosis), and common carotid artery. Pearson correlation compared the CSI estimate of the carotid bulb to the actual carotid bulb measurement. Ratio calculations of the stenosis were performed using (1) CSI carotid bulb estimate and (2) actual carotid bulb measurement as denominator data. A paired-sample Wilcoxon signed rank test compared the results of these 2 ratio measurements per carotid.
  
  
  RESULTS
  Interobserver variability was good to excellent (0.64 to 0.87). The CSI estimate of the carotid bulb size overestimated the measured carotid bulb by an average of 1.5 mm in a random distribution (correlation=0.39, N=151). Paired-sample Wilcoxon signed rank test demonstrated a significant difference between the 2 sets of ratios (z-value of -9.87, P<0.001).
  
  
  CONCLUSIONS
  Direct measurement of carotid stenosis, vessel wall soft tissues, and computed tomography plaque imaging is now possible with the high-resolution anatomic data present in high-speed computed tomography angiography, alleviating the need for ratios and inaccurate mathematic estimations of carotid anatomy for carotid stenosis quantification.
authors.affiliation: Northwestern University, 676 North St. Clair St, Ste 1400, Chicago, IL 60611, USA. ebartlett5544@rogers.com
authors.forename: Eric S
authors.initials: ES
authors.lastname: Bartlett
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Walters
authors.forename: Sean P
authors.initials: SP
authors.lastname: Symons
authors.forename: Allan J
authors.initials: AJ
authors.lastname: Fox
mesh_terms: D002339:Carotid Arteries / Q000000981:diagnostic imaging*; D016893:Carotid Stenosis / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography / Q000379:methods / Q000592:standards; D006801:Humans; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards