TRICKS AND TIPS IN DUPLEX ULTRASOUND OF CAROTID ARTERIES
Antignani P. L.
Director Vascular Centre, Nuova Villa Claudia, Rome, Italy
President of the International Union of Angiology
Following cardiac disease and cancer, stroke continues to be the third leading cause of death and disability due to chronic disease in the developed world. Appropriate screening tools are integral to early detection and prevention of major cardiovascular events. In a carotid artery, the presence of increased intima‐media thickness, plaque, or stenosis is associated with increased risk of a transient ischaemic attack or a stroke.
Carotid artery ultrasound remains a long‐standing and reliable tool in the current armamentarium of diagnostic modalities used to assess vascular morbidity at an early stage. The procedure has, over the last two decades, undergone considerable upgrades in technology, approach, and utility. One of the main indications for a carotid ultrasound scan is the assessment of cerebrovascular risk. The presence of atherosclerotic plaques clearly points to an increased risk (not only for stroke, but also for coronary artery disease and peripheral vascular disease).
Ultrasound is the primary diagnostic tool to screen for carotid artery disease. It is simple, inexpensive and widely available. Especially the area of the bifurcation, where the wide majority of stenotic lesions are located, can easily be assessed with ultrasound. Compared to other imaging modalities such as CT-angiography, digital subtraction angiography and magnetic resonance angiography, carotid ultrasound also allows haemodynamic assessment of stenosis. In the majority of situations, ultrasound can be used as the sole method for the assessment and follow up of carotid artery stenosis.
A carotid colour flow duplex scanning allows to define the intima-media thickness (IMT), to quantify the stenosis, and to assess its morphological characteristics. The carotid colour flow duplex is the best method for screening and for the definition of lesions. Imaging methods have the potential to be used as a screening tool for the presence of atherosclerosis and the degree of stenosis. Imaging also helps to distinguish stable from vulnerable plaques, and ultimately to distinguish patients with low versus those with high risk of cardiovascular complications. Good expertise of the operator and the high-quality apparatus are essential for reliable outcome. The enhancement of images (gray scale, 3D, CEUS, TDI, AWM) provides useful information but it is difficult to use in daily practice.
Additional imaging modalities are indicated if the image quality is poor, and one is not certain if a stenosis is present or not. For preoperative/interventional planning in the symptomatic carotid artery disease, if the ultrasound does not allow a reliable quantification of the degree of stenosis (especially in severely calcified lesions), an intracranial stenosis/occlusion is suspected, and collaterals should be assessed.
Additional CT angiography in combination with intracranial CT is indicated to correlate intracranial vascular disease with the findings of CT angiography/ultrasound, and to correlate these findings with symptoms, and in acute stroke.