Comparison of ultrasound and IV-DSA for carotid evaluation

Sixty carotid bifurcations in 34 symptomatic patients were examined prospectively with ultrasound (continuous wave Doppler and high resolution, B-mode imaging) and intravenous digital subtraction angiography (IV-DSA). The overall quality of examination was better with DSA than with ultrasound. Imaging of the external carotid artery was particularly difficult with sonography. For evaluation of the common and internal carotid arteries, eight percent of IV-DSA studies were poor or inadequate as compared with 12% for B-mode imaging. Overall for detection of atherosclerotic plaque, high resolution B-mode sonography was 84% sensitive and DSA 81% sensitive. When only the common and internal carotid arteries were considered, the sensitivity of high resolution sonography improved to 93% and the sensitivity of IV-DSA increased to 86%. Ultrasound (combined high resolution, B-mode sonography and CW Doppler) correctly identified all six internal carotid occlusions in the series. While IV-DSA correctly identified five of the six occlusions, the sensitivity for detection of lesions causing 70% or more stenosis was 95% for both ultrasound and IV-DSA. Sensitivity for 50% or greater obstruction was 79% for ultrasound and 85% for IV-DSA. Ultrasound sensitivity for greater than 50.9% stenoses rose to 87% when only the common and internal carotid were considered while IV-DSA sensitivity remained at 85%. Specificity was good at all levels of obstruction. It may be concluded from this study that the accuracy of ultrasound and IV-DSA are quite similar for evaluation of the carotid bifurcation and that either test is a satisfactory screening method for carotid bifurcation atheromatous disease.