An ultrasound of the body’s two carotid arteries, which are located on each side of the neck and carry blood from the heart to the brain, provides detailed pictures of these blood vessels and information about the blood flowing through them.
A Doppler ultrasound study will be a part of a carotid ultrasound examination.
Doppler ultrasound is a special ultrasound technique that evaluates blood velocity as it flows through a blood vessel, including the body's major arteries and veins in the abdomen, arms, legs and neck.
Doppler ultrasound, a special application of ultrasound, measures the direction and speed of blood cells as they move through vessels. The movement of blood cells causes a change in pitch of the reflected sound waves (called the Doppler effect).
For most ultrasound exams, the patient is positioned lying face-up on an examination table that can be tilted or moved.
A clear water-based gel is applied to the area of the body being studied to help the transducer make secure contact with the body and eliminate air pockets between the transducer and the skin. The sonographer or radiologist then presses the transducer firmly against the skin and sweeps it over the area of interest.
Doppler sonography is performed using the same transducer.
This ultrasound examination is usually completed within 15 minutes.
The carotid ultrasound is most frequently performed to detect narrowing, or stenosis, of the carotid artery, a condition that substantially increases the risk of stroke.
The major goal of carotid ultrasound is to screen patients for blockage or narrowing of their carotid arteries, which if present may increase their risk of having a stroke. Once the diagnosis is made a comprehensive treatment may be initiated.
It may also be performed if a patient has high blood pressure or a carotid bruit (pronounced brU-E)—an abnormal sound in the neck that is heard with the stethoscope.
Other risk factors calling for a carotid ultrasound are:
- advanced age
- elevated blood cholesterol
- a family history of stroke or heart disease
A carotid ultrasound is also performed to:
- locate a hematoma, a collection of clotted blood that may slow and eventually stop blood flow.
- detect dissection of the carotid artery, a split between layers of the artery wall that may lead to obstruction of blood flow or a weakening of the wall of the artery.
- check the state of the carotid artery after surgery to restore normal blood flow.
- verify the position of a metal stent placed to maintain carotid blood flow.
Doppler ultrasound images can help the physician to see and evaluate:
- blockages to blood flow (such as clots).
- narrowing of vessels (which may be caused by plaque).
- tumors and congenital malformation.
What are the limitations of Carotid Ultrasound Imaging?
- Carotid ultrasound may be difficult or impossible if a patient has a dressing covering a wound or surgical scar in the neck.
- An occasional patient is difficult to examine because of the size or contour of the neck.
- Calcium deposits in the wall of the carotid artery may make it difficult to evaluate the vessel.
- A small amount of soft plaque that produces low-level echoes may go undetected.
- Ultrasound cannot visualize the entire length of the vessel because the last portion of the carotid artery travels though the bone at the base of the skull. For a complete assessment, patients may need to undergo a CT or MRI of the carotid.