Imaging of high-risk carotid plaques: ultrasound.

Duplex ultrasonography has a well-established role in the assessment of the degree of stenosis caused by carotid atherosclerosis. This assessment is derived from Doppler velocity changes induced by the narrowing lumen of the artery. New research into the mechanisms for plaque rupture and atheroembolic stroke indicates that the degree of narrowing is an imperfect predictor of stroke risk, and that other factors, such as plaque composition and remodeling and biomechanical forces acting on the plaque, can play a role. New advances in ultrasound imaging technology have made it possible to investigate these measures of plaque vulnerability to identify pre-embolic unstable carotid plaques. Efforts have been made to quantify the morphologic appearance of the plaque in B-mode images and to correlate them with histology. Additional research has resulted in the first generation of clinically available 3-dimensional ultrasound transducers that reduce operator-dependence and variability. Finally, ultrasonography provides real-time imaging and physiologic information that can be utilized to measure disruptive forces acting on carotid plaques. We review some of these exciting developments in ultrasonography and discuss how these may impact clinical practice.