CTA quantification of internal carotid artery stenosis: application of luminal area vs. luminal diameter measurements and assessment of inter-observer variability.

Background And Purpose: In contrast to digital subtraction angiography (DSAdia), computed tomography angiography (CTA) provides exact delineation of the perfused lumen in the axial plane, thus allowing luminal (CTAdia) as well as cross-sectional area (CTAarea) internal carotid artery stenosis (ICAS) assessment. The purposes of the present study were to correlate CTAdia and CTAarea with DSAdia and to assess the inter-observer variabilities of both CTA techniques.

Methods: In a retrospective analysis, CTA images were reviewed by two observers and ICAS was assessed according to North American Symptomatic Carotid Endarterectomy Trial applying CTAdia and CTAarea. DSAdia was assessed by a third observer.

Results: Based on 54 consecutive patients (40 males [74.1%] and 14 females [25.9%]; median age 73.3 years), ICAS percentages of CTAdia and CTAarea revealed significant correlations with DSAdia (r= 0.79-0.87, all P<.001) with median differences in the range of +8% to -6%. Inter-observer agreement was moderate for CTAdia (kappa= 0.60) and excellent for CTAarea (kappa= 0.86). Sensitivity of CTAarea for the detection of ICAS >70% was 100% for both observers, corresponding results for CTAdia were 97.1% and 71.4%, respectively, using DSAdia as the gold standard.

Conclusion: CTAarea assessment of ICAS correlates well with the results of DSAdia and provides an excellent sensitivity for the detection of ICAS >70% with superior inter-observer agreement compared to CTAdia.