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A carotid artery duplex scan is a type of vascular ultrasound study done to assess occlusion (blockage) or stenosis (narrowing) of the carotid arteries of the neck and/or the branches of the carotid artery. A carotid artery duplex scan is a noninvasive (the skin is not pierced) procedure.
This type of Doppler examination provides a 2-dimensional (2D) image of the arteries so that the structure of the arteries and location of an occlusion can be determined, as well as the degree of blood flow.
A transducer sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer (like a microphone) is placed on the carotid arteries at certain locations and angles, the ultrasonic sound waves move through the skin and other body tissues to the blood vessels, where the waves echo off of the blood cells.
The transducer picks up the reflected waves and sends them to an amplifier, which makes the ultrasonic sound waves audible. Absence or faintness of these sounds may indicate an obstruction to the blood flow.