ABSTRACT
In the early stages of disease, atherosclerosis is characterized by lipid-laden plaque accumulation in the arterial vasculature, whereas in later stages this is often replaced by fibrosis and calcification. Vulnerable plaque has come to be defined as an atherosclerotic plaque prone to disruption and/or thrombosis. The non-invasive and invasive ultrasound imaging modalities that have been used to identify vulnerable plaques include intravascular ultrasound (IVUS), transcutaneous ultrasound to visualize carotid arteries, and contrast echocardiography. Of these, carotid artery ultrasound is well established as a technique to diagnose and monitor early and progressive atherosclerosis. Recently, ultrasound plaque characterization has enabled the identification of lesions more prone to embolization during carotid stenting.1 Although transthoracic echocardiography has been used to visualize large epicardial coronary arteries, visualization of coronary plaque is limited by this technique. Miniaturization of ultrasound transducers and positioning them at the tip of smalldiameter catheters has made IVUS possible. When an IVUS catheter is placed in a coronary artery, an ultrasound beam is directed perpendicular to the course of the vessel and steered either electronically or mechanically throughout its 360° circumference. An image of crosssectional arterial anatomy is obtained,2 and in normal arteries these images
depict a sharp, bright endothelial/lumen border, a clear sonolucent media, and an echo-dense adventitia.3
