Thus, when the NASCET was designed, the measurement of percentage ICA stenosis was standardized angiographically by comparing the width of the residual lumen at its narrowest point with the diameter of the lumen of the distal normal ICA (beyond any post-stenotic dilation Fig. Hence, this method has significant interobserver and intraobserver variability as well as poor reproducibility. However, because the outer wall of the ICA can be seen on an angiogram only if it is calcified, angiographic measurements of ICA diameter are only estimates in many cases. 3 Before the NASCET, the percentage stenosis of the ICA was typically calculated by comparing the width of the residual lumen with the estimated diameter (outer wall to outer wall) of the ICA at the site of the stenosis ( Fig.
#Carotid doppler trial
The precise method of grading stenoses of the ICA changed with the publication of the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Numerous studies have shown that when it is performed appropriately, ultrasound examination of the carotid arteries is highly accurate for detection of surgical lesions (i.e., ICA stenoses ≥70%), 7 – 10 and additional confirmatory studies such as CT angiography, magnetic resonance angiography, and conventional angiography are usually unnecessary except in complex cases with discordant findings or poor visualization. Of these potential screening modalities, carotid ultrasound examination is the most readily available, least invasive, and least expensive.
Patients with risk factors for carotid plaque, carotid bruits, and symptoms of stroke or transient ischemic attacks are typically referred for evaluation of the carotid arteries, which can be performed with ultrasonography, computed tomographic angiography, magnetic resonance angiography, or conventional angiography. Risk factors for disease at the carotid bifurcation include atherosclerosis, hypertension, diabetes mellitus, hyperlipidemia, hypercholesterolemia, obesity, and smoking. Thus, the identification of patients with ICA stenoses of 60% to 70% is clearly important for patient management, allowing appropriate referral for carotid endarterectomy. 3 – 6 However, at the time these trials were published in the 1990s, statin therapy was not a part of the standard medical regimen, and double-blind trials comparing carotid endarterectomy with medical management including statin therapy are currently ongoing. 2 Carotid endarterectomy has been convincingly shown in several prospective multicentered, randomized, double-blind trials to significantly reduce the risk of stroke and death in patients with stenoses of the internal carotid artery (ICA) of more than 60% to 70% compared with optimized medical therapy. Whereas the heart is the number one source, 20% to 30% of strokes are believed to be secondary to embolus from plaque or thrombus at the carotid bifurcation. 1 Most strokes are due to thromboembolic events rather than to ischemia or reduced perfusion. Stroke remains the third leading cause of death and is a major cause of morbidity in the United States. Using the Doppler effect-the change in the frequency of sound or light waves as they bounce off a moving object-this kind of ultrasound produces an image of blood in motion.Leslie M. A computer transforms these echoes into an image that is displayed on a monitor.ĭoppler ultrasound is a variation of this technique that not only shows internal structures but also examines the flow of blood through blood vessels. The transducer sends sound waves into your body and picks up the echoes of the sound waves as they bounce off internal organs and tissue.
#Carotid doppler skin
After coating a small area of your skin with a lubricant to reduce friction, a radiologist or ultrasound technician places an ultrasound transducer, which looks like a microphone, on your skin and may rub it back and forth to get the right view. This imaging technique works in a manner similar to radar and sonar, developed in World War II to detect airplanes, missiles, and submarines that were otherwise invisible. Ultrasound uses sound waves instead of radiation to generate snapshots or moving pictures of structures inside the body.
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