Various methods including MRI plaque imaging have been used to evaluate carotid artery plaques, but ultrasonography, which can be performed readily and non-invasively at the bedside, is excellent for follow-up examination and rapid diagnosis in emergency situations. Conventionally, ultrasound examination of carotid artery plaques has focused on vascular stenosis due to plaques and emphasized quantitative aspects such as the degree of stenosis. Clinically, however, some plaques resist treatment and repeatedly cause ischemic events despite a relatively low degree of stenosis. In such cases, qualitative diagnosis based on the evaluation of plaque vulnerability is important. In addition to the items that have been conventionally evaluated, such as the plaque echogenicity, ulceration, and mobility, evaluation of diverse aspects of plaques has become possible due to the advent of new ultrasound techniques. Plaque neovascularization can be evaluated by contrast-enhanced ultrasound (CEUS), visualization of slow blood flows has become possible without the use of a contrast agent by superb micro-vascular imaging (SMI), and detailed morphology and volume can now be examined using a 3D probe. Moreover, because of the excellent portability of ultrasound devices, the evaluation of plaque properties is occasionally useful for the planning of the therapeutic strategy in the acute phase of cerebral infarction. Thus, ultrasonography can provide a wide range of diagnostic information.
