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.