Plaque characterization by B-mode scan.

High-resolution ultrasound technology provides anatomic information on the nature of the vessel wall. As such, it is a complementary modality to both frequency analysis, which provides flow data, and angiography, which describes vessel lumen. At present, the technology is most effectively applied to superficial vessels such as the carotid, common femoral, and popliteal arteries. Measurement can be compromised by heavy vessel calcification, and the technique is most useful in mild to moderate disease. Prospective blinded trials have shown that HRUS can be used to determine lumen diameter and per cent stenosis, although its accuracy is improved by adding frequency analysis. The technique is most useful for interrogating the atherosclerotic plaque itself; as such, it appears superior to angiographic techniques. Several investigators have documented the ability of HRUS to characterize plaque and particularly to identify intraplaque hemorrhage and ulceration. Criteria for diagnosis remain difficult to standardize and, for the moment, must be developed for each center involved in these studies. The future of HRUS appears to lie in development of more detailed analyses of plaque morphology and the study of atherosclerotic disease in large populations over time.