Efficacy of MR angiography in the detection and characterization of occlusive disease in the vertebrobasilar system

Purpose: The purpose of this work was to determine the efficacy of MR angio graphy (MRA) in the detection and characterization of occlusive disease in the vertebrobasilar system. Method: We retrospectively reviewed the posterior circulation registry of o ur institution to select 42 consecutive patients with posterior circulation ischemic symptoms who underwent both MRA and angiography. The extracranial vertebral arteries (ECVAs) were examined by two-dimensional time-of-flight MRA above the C6 level, and the intracranial vertebral arteries (ICVAs) an d basilar arteries (BAs) were examined by three-dimensional time-of-flight MRA. Sixty-two ECVAs, 63 ICVAs, and 39 BAs were examined by the readers. Results: Occlusive disease was seen on angiography in 22 of the 42 patients . The sensitivity and specificity values for detection of lesions in 12 ECV A, 19 ICVA, and 12 BA abnormalities were as follows: ECVA, 92 and 96% for R eader A and 100 and 90% for Reader B: ICVA, 84 and 93% for Reader A and 74 and 82% for Reader B; and BA, 100 and 88% for Reader A and 100 and 78% for Reader B, For ICVA, the sensitivity of MRA was less than that of angiograph y because of lesions missed by the readers at the junctional area of the ex tra- and intracranial MRA. MRA accurately characterized 9 of the 12 (75%) E CVA, 10 of the 19 (43%) ICVA, and 11 of the 12. (92%) BA lesions. Conclusion: MRA is an effective method for detection of occlusive lesions i n the ECVAs and BAs. Clinically important lesions can be missed by MRA in t he ICVA. MRA is more accurate in characterization of occlusive lesions in B As than in ECVAs or ICVAs.