Carotid Ultrasound is a diagnostic procedure that uses high-frequency sound waves to generate images of the neck's internal carotid artery. It is used to measure the plaque build-up in your carotid arteries. Carotid arteries supply blood to your brain. Plaque build-up can reduce the blood flow and sometimes completely block the artery causing stroke. Candidates for carotid artery ultrasound are those who are at high risk for, or beginning to display the symptoms of, carotid artery disease. Candidates include those who have recently had a stroke or carotid artery surgery; have an abnormal sound in, or damage to the walls of, a carotid artery; or are suspected of having blood clots in a carotid artery. High-risk candidates for carotid artery disease include those who have been diagnosed with diabetes or high cholesterol, or have a family history of heart disease.