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Hypertension & Stroke


Carotid artery doppler ultrasound


This test uses a technique called Doppler ultrasound to measure blood flow through the carotid arteries inside the neck, which supply blood to the brain. A device called a transducer is passed lightly over the neck, directing high-frequency sound waves (ultrasound) into the carotid arteries. The sound waves are reflected back at frequencies that correspond to the velocity of blood flow, and are converted into audible sounds and graphic recordings.

Duplex scanning combines Doppler ultrasound with real-time ultrasound imaging of the carotid arteries, allowing calculation of the percent of narrowing in the vessels. Images are displayed on a viewing monitor and may also be recorded on film or video for later examination.

Purpose of the Test

To assess blood flow in the carotid arteries and detect any blockages, such as blood clots or atherosclerosis (narrowing due to the buildup of plaques).

Who Performs It

A doctor or a technician who is trained in ultrasound.

Special Concerns


Before the Test

No special preparation is necessary.

What You Experience

You will lie on your back on an examination table, and your head will be supported to inhibit movement.

A water-soluble gel is applied to the skin on your neck to enhance sound wave transmission.

The examiner then moves the transducer back and forth over one side of your neck to obtain different views of the carotid artery. The other side of your neck is then checked in the same way.

Once clear images of the carotid artery are obtained, they are recorded on film or video for later analysis.

The test takes about 15 to 30 minutes.

Risks and Complications

Ultrasound is painless, noninvasive, and involves no exposure to radiation. There are no associated risks.

After the Test

The examiner removes the conductive gel from your skin.

You may resume your normal activities.


A physician reviews the recorded images and other test data for evidence of abnormalities. High blood flow velocity indicates narrowing of the carotid arteries.

If the carotid arteries are blocked, appropriate therapy will be initiated to reduce your risk of stroke.

In some cases—especially if surgery to remove carotid blockages is contemplated—additional diagnostic tests, such as arteriography, may be ordered to determine the exact location and extent of the occlusive plaques.


From The Johns Hopkins Consumer Guide to Medical Tests. You can order this book now on our secure server



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