by Diane Ursu

Created on: July 18, 2009

Cardiovascular disease is the hardening and blockage of the arteries. Arterial blockages in the legs can cause numbness and cramping. Blockages in heart can lead to heart attack, resulting in cardiac tissue death. Blockages also occur in the carotid arteries, the arteries on each side of the neck leading to the face and brain.

The common carotid arteries arise from the brachiocephalic artery on the right, and the subclavian artery on the left. Each common carotid artery bifurcates, or branches, into the internal and external carotid arteries near the ear. The internal carotid artery feeds the brain, while the external carotid artery feeds the superficial structures of the face. The carotid bifurcation is called the bulb. This is where plague is most likely to build up, causing stenosis. Ultrasound is used to evaluate carotid stenosis and is done by a sonographer, a person who specializes in obtaining ultrasound images. Ultrasound is non-ionizing radiation, so it is safe when compared with x-ray.

Patient Positioning

The patient lies flat on his or her back for 30 to 60 minutes. For this reason, it is important to make any necessary adjustments, such as placing a pad or pillow under the knees to alleviate back pain. The head must rest on a relatively flat pillow to allow room for the transducer, or camera, to move between the shoulder and ear. The head will be slightly tilted away from the side that will be scanned. The patient must be as still as possible, so there can be no talking, excessive swallowing, or coughing.

Protocol

Sonographers generally use a 7 to 10 MHz transducer for carotid ultrasound. Ultrasound gel is applied to the area to be scanned. The gel allows the ultrasound waves to freely move between the transducer and the neck so an image can be produced.

Both carotid arteries are examined. The common and internal carotid arteries are imaged in three spots - proximal, mid, and distal. One measurement is taken at the bulb and in the external carotid artery. Each segment of artery is evaluated by obtaining a two-dimensional image, a color Doppler image demonstrating direction of blood flow and filling of the artery, and a pulsed Doppler image showing spectra demonstrating the velocity of the blood flow.

The tunica intima, the inner layer of the artery, is measured proximal to the bulb (proximal is closest to the heart) in the two-dimensional image. A two-dimensional image of the bifurcation is acquired for the bulb, although it is not always

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