Carotid ultrasonography

Carotid ultrasound is a low-cost, noninvasive, and accurate diagnostic imaging modality used to evaluate diseases of the carotid arteries.[2] It is most often used to diagnose carotid artery stenosis, a form of atherosclerosis, and has the capability to assess plaque morphology and characteristics.[1] Carotid artery stenosis is a major risk factor for stroke, and risk assessment of atherosclerotic carotid plaques is a critical component of stroke prevention. Advances in imaging have allowed for risk stratification including degree of stenosis and how vulnerable the atherosclerotic plaque is to rupture. Other plaque features that contribute to stroke risk and can be evaluated by imaging are: intraplaque hemorrhage, plaque ulceration and neovascularization, fibrous cap thickness, and presence of a lipid-rich necrotic core (LNRC).[1] Carotid ultrasound is the preferred initial diagnostic test to evaluate carotid artery stenosis,[2] and can also be used to monitor response to lipid-lowering therapy.[1]

While ultrasound is able to assess plaque morphology, it is limited in both specificity and sensitivity in assessing lipid-rich necrotic core, plaque hemorrhage, and ulceration when compared to the gold standard.[1] When diagnosing carotid artery stenosis, carotid ultrasound has a lower sensitivity than MRA but is more sensitive than CTA. However, both CTA and MRA have a higher specificity.[2]

A major limitation of carotid ultrasound is a high degree of inter-/intraobserver variability; however, computerized algorithms used for evaluation of the intima-media thickness (IMT), a measure of plaque morphology, have helped minimize the degree of variability.[2] Carotid ultrasound is dependent on operator skill, and other noted areas of limitation are poor insonation angle, poor blood flow, and deep artery location.[2] CEUS is prone to overinterpretation of vessel wall abnormalities, known as pseudoenhancement.[1]

• Medical ultrasonography