Combined linear array high- and convex array low-frequency duplex ultrasonography with or without examination of the ophthalmic artery in the differential diagnosis of occlusion from severe stenosis of internal carotid artery.

PURPOSE

To assess the benefits of using a low-frequency convex probe and detecting ophthalmic artery blood flow for the differential diagnosis of occlusion from severe stenosis of the internal carotid artery (ICA).

METHODS

A total of 103 patients were enrolled and had three sequential examinations by an experienced sonographer. First, the proximal ICA was examined with a 5.0-7.5-MHz linear probe. Second, the distal ICA was examined with a 3.5-5.0-MHz convex probe. Third, the ophthalmic artery (OA) was examined with a 5.0-7.5-MHz linear probe. Three parallel sets of diagnoses were made based on results from (1) high-frequency ultrasonography; (2) combined use of high- and low-frequency ultrasonography; and (3) combined use of high- and low-frequency ultrasonography along with OAs examination findings. Efficiencies of the three diagnoses were compared by receiver operating characteristic curves with digital subtraction angiography as the gold standard.

RESULTS

The second diagnostic approach yielded the highest sensitivity (96.6%) and specificity (94.5%). OA blood flow was reversed in most, but not all, cases of ICA occlusion (27/29). Areas under the receiver operating characteristic curves of the three diagnoses were significantly different (p < 0.05).

CONCLUSIONS

The diagnostic performance of combined high- and low-frequency ultrasonography is greater than that of high-frequency ultrasonography alone. Although OA examination does not increase the diagnostic performance, it provides helpful data for the assessment of hemodynamics and collateral circulation.