by Dr Pandula Siribaddana

Created on: August 19, 2009   Last Updated: September 17, 2009

Carotid arteries are the main blood supply to the brain and are running on either side of the neck as left and right carotid arteries. In the upper segment of the neck, the carotid artery divides itself into internal and external carotid arteries before entering the skull.

Due to its extreme importance in the proper functioning of the brain, any alteration in the blood flow would result in detectable symptoms that could range from fatal stroke to a mild syncope. In investigating such events, the main focus will be put on the carotid arteries of the neck. The technique used in assessing these arteries is known as 'Carotid Doppler ultrasound'.

The Carotid Doppler Ultrasound makes use of high frequency sound waves in order to detect the abnormalities of the blood vessels. Due to the use of sound waved it shows several advantages over other imaging methods.

1. Less costly

2. No radiation

3. Does not cause claustrophobia as in MRI scans

4. Easy transportation of the equipment

5. Does not require anesthesia

6. Not necessary to inject dye

The physiology behind the Carotid Doppler is twofold,

1. Pulse- echo method - Which refers to the sending of a sound wave and receiving back the same wave. The difference in time of receiving and the angle will demarcate the different layers of the blood vessel.

2. Doppler phenomenon - This technique is used in assessing the velocity of the blood flow and the sound waves that are sent will return after rebounding on the blood with a different frequency. The change in frequency as well as the difference in time will decide the velocity and the direction.

Backed by these physiological principles, the Carotid Doppler is able to assess the following,

1. The wall thickness of the blood vessels

2. Narrowing of the blood vessel lumen

3. Amount of narrowing in the lumen

4. Constituents of any deposits in the blood vessel lumen

5. Direction of the blood flow

6. Velocity of the blood flow

The vessel wall narrowing will be demonstrated by a faster velocity of the blood and calcium deposits will be illustrated as a hyper echogenic pattern.

The Carotid Doppler Ultrasound will be performed by a radiologist, a vascular surgeon or a trained technician. The ultrasound probe will be applied to the neck area which will be usually covered with a thin layer of gel. The procedure will be pain free and non invasive. Depending on the experience of the investigator it will take 10 - 20 minutes for a complete assessment.

Learn more about this author, Dr Pandula Siribaddana.
Click here to send this author comments or questions.