B-flow imaging for assessment of 70% to 99% internal carotid artery stenosis based on residual lumen diameter.

OBJECTIVE: The purpose of this study was to use B-flow imaging (BFI) to investigate whether the minimal residual lumen diameter (MRLD) measurement can be used in place of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method of measurement. METHODS: One hundred sixty-three consecutive patients with internal carotid artery (ICA) stenosis were examined with BFI and digital subtraction angiography. The diagnostic performances of the NASCET method of measurement with the BFI and MRLD measurements in determining 70% to 99% ICA stenosis were compared by performing receiver operating characteristic curve analysis. RESULTS: There was no difference between the performances of the two methods in estimating 70% to 99% ICA stenosis (area under the receiver operating characteristic curve was 0.979 for the NASCET method and 0.978 for the MRLD measurement; P = .899). In the assessment of ICA stenosis, an MRLD measurement of 1.5 mm was determined as the optimal threshold value. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of this threshold were 93%, 94%, 84%, 97%, and 94%, respectively. CONCLUSIONS: In the BFI examination, when the distal ICA, which is the denominator in the NASCET method of measurement, cannot be measured at all or cannot be measured accurately, an MRLD measurement that is equal to or less than 1.5 mm is the criterion that can be used with confidence in determining 70% to 99% ICA stenosis.