Carotid (ka-ROT-id) ultrasound is a painless and harmless test that uses high-frequency sound waves to create pictures of the insides of your carotid arteries.
You have two common carotid arteries, one on each side of your neck. They each divide into internal and external carotid arteries.
The internal carotid arteries supply oxygen-rich blood to your brain. The external carotid arteries supply oxygen-rich blood to your face, scalp, and neck.
Carotid ultrasound shows whether a waxy substance called plaque (plak) has built up in your carotid arteries. The buildup of plaque in the carotid arteries is called carotid artery disease.
Over time, plaque can harden or rupture (break open). Hardened plaque narrows the carotid arteries and reduces the flow of oxygen-rich blood to the brain.
If the plaque ruptures, a blood clot can form on its surface. A clot can mostly or completely block blood flow through a carotid artery, which can cause a stroke.
A piece of plaque or a blood clot also can break away from the wall of the carotid artery. The plaque or clot can travel through the bloodstream and get stuck in one of the brain's smaller arteries. This can block blood flow in the artery and cause a stroke.
A standard carotid ultrasound shows the structure of your carotid arteries. Your carotid ultrasound test might include a Doppler ultrasound. Doppler ultrasound is a special test that shows the movement of blood through your blood vessels.
Your doctor might need results from both types of ultrasound to fully assess whether you have a blood flow problem in your carotid arteries.
A carotid ultrasound shows whether you have plaque buildup in your carotid arteries. Over time, plaque can harden or rupture (break open). This can reduce or block the flow of oxygen-rich blood to your brain and cause a stroke.
Your doctor may recommend a carotid ultrasound if you:
Your doctor also may recommend a carotid ultrasound if he or she thinks you have:
A carotid ultrasound also might be done to see whether carotid artery surgery, also called carotid endarterectomy (END-ar-ter-EK-to-me), has restored normal blood flow through a carotid artery.
If you had a procedure called carotid stenting, your doctor might use carotid ultrasound afterward to check the position of the stent in your carotid artery. (The stent, a small mesh tube, supports the inner artery wall.)
Carotid ultrasound sometimes is used as a preventive screening test in people at increased risk of stroke, such as those who have high blood pressure and diabetes.
Carotid ultrasound is a painless test. Typically, there is little to do in advance of the test. Your doctor will tell you how to prepare for your carotid ultrasound.
Carotid ultrasound usually is done in a doctor's office or hospital. The test is painless and often doesn't take more than 30 minutes.
The ultrasound machine includes a computer, a screen, and a transducer. The transducer is a hand-held device that sends and receives ultrasound waves.
You will lie on your back on an exam table for the test. Your technician or doctor will put gel on your neck where your carotid arteries are located. The gel helps the ultrasound waves reach the arteries.
Your technician or doctor will put the transducer against different spots on your neck and move it back and forth. The transducer gives off ultrasound waves and detects their echoes as they bounce off the artery walls and blood cells. Ultrasound waves can't be heard by the human ear.
The computer uses the echoes to create and record pictures of the insides of the carotid arteries. These pictures usually appear in black and white. The screen displays these live images for your doctor to review.
Your carotid ultrasound test might include a Doppler ultrasound. Doppler ultrasound is a special test that shows the movement of blood through your arteries. Blood flow through the arteries usually appears in color on the ultrasound pictures.
You usually can return to your normal activities as soon as the carotid ultrasound is over. Your doctor will likely be able to tell you the results of the carotid ultrasound when it occurs or soon afterward.
A carotid ultrasound can show whether plaque buildup has narrowed one or both of your carotid arteries. If so, you might be at risk of having a stroke. The risk depends on the extent of the blockage and how much it has reduced blood flow to your brain.
To lower your risk of stroke, your doctor may recommend medical or surgical treatments to reduce or remove plaque from your carotid arteries.
Carotid ultrasound has no risks because the test uses harmless sound waves. They are the same type of sound waves that doctors use to record pictures of fetuses in pregnant women.
The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.
NHLBI-supported research has led to many advances in medical knowledge and care. For example, this research has helped evaluate tests for many diseases and conditions.
The NHLBI continues to support research on various tests, including carotid ultrasound. For example, the NHLBI currently sponsors a study to explore how cost-effective a new ultrasound device is for screening people who are at risk for carotid artery stenosis (narrowing of the carotid arteries).
Much of the NHLBI's research depends on the willingness of volunteers to take part in clinical trials. Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions.
For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.
By taking part in a clinical trial, you may gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.
If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.
If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.
For more information about clinical trials related to carotid ultrasound, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.