A carotid ultrasound is a test that provides images of the carotid arteries in the neck, telling us how much blood flows through them and how fast it travels. Ultrasound waves are used to make an image of the arteries that can be used to detect abnormalities and blockages that may lead to stroke. Physicians often request carotid ultrasound for patients who have had a stroke or who might be at high risk for a stroke. This test is not necessary if a CT angiogram has been performed unless there is a question that requires a second mode of evaluation.

A transcranial Doppler (or TCD) test also uses ultrasound, but it focuses on the evaluation of flow in the major arteries inside the skull.

How a carotid ultrasound or TCD works

The patient lies down on the exam table as the physician (or technician) places a clear water-based gel on both sides of the neck where the carotid arteries are located. The gel acts as a lubricant that allows the transducer (a device that both puts out and detects ultrasound signals) to slide around easily on the patient’s skin. In the case of a TCD, the gel may be placed on the temples, on eyelids, under the jaw and at the base of the neck.

Images of the artery will be shown on a video screen when the transducer is placed on the skin. The physician or technologist performing the scan may occasionally reposition the transducer in order to view these arteries from many different angles.

The procedure is completely noninvasive with no risks of pain or radiation. A carotid ultrasound usually takes between 15 and 30 minutes (or up to an hour along with a TCD), and results are generally available immediately.