Duplex ultrasound, MR angiography and Conventional angiography in Carotid artery disease: interpretation of separate test results and their combinations.
Purpose: To compare duplex ultrasound (DUS) and MR angiography (MRA) with conventional intra-arterial digital subtraction angiography (DSA) in patients with carotid artery disease. Methods: Between 1996 and 2000 375 consecutive patients with symptomatic carotid artery stenosis undergoing evaluation prior to endarterectomy were included. All patients with a peak systolic velocity (PSV) > 150 cm/sec measured on DUS subsequently underwent DSA and MRA. In the last phase of our study a subgroup of 40 patients additionally underwent contrast-enhanced MRA (CE-MRA). Standardized cutoff criterions based on PSV s were used to asses the degree of stenosis with DUS. The degree of stenosis on MRA was analyzed by means of the criteria used in the North American Endarterectomy Trial (NASCET). DSA served as the standard of reference. Results: DUS analyzed with standardized PSV criterions resulted in a sensitivity of 90% and a specificity of 83% in identifying severe ICA stenosis (70–99%). Stenosis measurements (NASCET) carried out on 3D-TOF MR angiograms yielded a sensitivity of 90% and a specificity of 84%. MRA had a tendency to overestimate the degree of stenosis compared with DSA. Combining MRA and DUS results, agreement between these two modalities (80% of carotids) gave a sensitivity of 98% and a specificity of 90%. In case of disagreement these numbers strongly decreased precluding meaningful diagnosis, MRA however performed slightly better than DUS did. Preliminary results of CE-MRA indicated good visibility, decrease of artifacts and accurate diagnostic performance. Conclusions: Both DUS and MRA seem accurate diagnostic tests to detect carotid artery stenosis using DSA as the standard of reference. MRA has the tendency to overestimate stenosis. Combining test results gives additional value in diagnostic outcome. Agreement between DUS and MRA results in higher sensitivity and specificity then disagreement between these modalities does. In case of disagreement MRA performs better then DUS, but DSA still seems recommendable. CE-MRA shows promising preliminary results.