Comparison of intra-arterial digital subtraction angiography, magnetic resonance angiography and duplex ultrasonography for measuring carotid artery stenosis

Background: Duplex ultrasonography and magnetic resonance angiography (MRA) are becoming competitive alternatives to angiography for determining the d egree of internal carotid artery (ICA) stenosis. Varying reports have been published regarding the suitability of each technique for grading ICA disea se. This retrospective study compared the merits of these three modalities for measuring ICA stenosis. Methods: One hundred and eleven patients being considered for carotid endar terectomy underwent intra-arterial digital subtraction angiography (DSA) vi a arch injection. Duplex imaging was performed in all patients and MRA. in 50. The degree of carotid stenosis estimated by the three modalities was co mpared. Results: There was good correlation between subjectively graded MRA and DSA images (r = 0.87, P < 0.001, n = 82 carotids) but poor correlation for obj ective estimates. MRA tended to underestimate the degree of stenosis (bias -4.5 per cent) compared with DSA, but showed good correlation with duplex u ltrasonography estimates r = 0.86, P < 0.001, n = 87 carotids). Both non-in vasive modalities produced high values of sensitivity and specificity in es timating stenoses of greater than 70 per cent. MRA was less sensitive for d istinguishing between severe stenosis and complete occlusion. Conclusion: This study did not resolve the debate regarding the method of c hoice as both MRA and duplex ultrasonography were accurate for imaging caro tid stenoses.