Doppler Neurosonology Laboratory: A Patient Guide
What is a carotid ultrasound?
A carotid ultrasound is a test that uses ultrasound waves to examine the arteries in the neck. These arteries are called carotid arteries and they are the major arteries that carry blood to the brain. Carotid ultrasound is a non-invasive, safe and painless procedure that helps doctors to detect hardening of the carotid arteries (atherosclerosis) or any blockage in the arteries.
How does carotid ultrasound work?
The principles of ultrasound: The probe (transducer) sends ultrasound waves and receives the reflected ultrasound waves from the arteries. A computer uses the information coming from the probe to construct ultrasound images of the neck arteries and compute blood flow velocities. The images are displayed on an ultrasound machine screen, printed on paper and videotaped. The principles of measuring blood flow velocities within arteries: To measure and calculate the velocities of the circulating blood within arteries of the neck an ultrasound machine uses the "doppler principle" or "doppler effect", named after christian doppler (1803-1853), the austrian physicist who developed the famous principle. The doppler principle is based on the fact that sound waves from a moving source are compressed or expanded, or that the frequency changes depending on whether the source is mowing towards (compressed) or away (expanded) from the observer. The doppler effect was used to confirm that the universe is expanding.
In 1842, doppler made an equation about the frequency and relative movement of sound source and observer. Doppler conducted a unique experiment to prove his theory. For two days, doppler had a train pull repeatedly at different speeds a freight car with trumpeters playing on top of it. He then had a musician capable of determining the differences in sounds record the height of the notes played as the train moved closer (higher notes were recorded) or further away (lower notes were recorded). This effect proved doppler's theory superbly.
What does carotid ultrasound show?
A carotid ultrasound test shows the walls of the carotid arteries and measures the blood flow velocities within arteries.
There are various abnormalities that can be detected by carotid ultrasound. These abnormalities can be mild, such as hardening or thickening of the wall of the carotid arteries, to severe such as large plaques (large clot in the arteries) that obstruct the blood flow.
When the blood flow is severely obstructed by plaque in the carotid arteries (arrow), a stroke can occur. This process is similar to the build up of plaque in the arteries to the heart that causes heart attacks. Since strokes occur in the brain, many doctors today refer to strokes as "brain attacks".
Stroke is the 3rd leading cause of death in the us today. Even stroke survivors are frequently left with permanent physical and mental disabilities. More than $70 billion are spent each year in this country to care for stroke and stroke survivors. The only way to save these lives, save the function of these limbs, and save the billions of dollars spent is to prevent stroke! Strokes due to carotid artery disease may be prevented. Severe carotid artery disease can be easily detected with this simple ultrasound examination that takes less than 30 minutes! You could nap right through this test and it might save your life!
A simple ultrasound scan can quickly and easily tell if you have severe carotid disease. If you have a little bit of plaque the goal is to prevent it from becoming worse! When plaques grow to the point where they cause a 60-70% blockage or more, or if they cause symptoms of stroke you may need treatment. This is where medical treatments and your own personal efforts can have a tremendous effect. Regular exercise, diet and various medications may prevent stroke. People with severe blockages in their carotid arteries should be considered for surgical treatment - called carotid endarterectomy. This procedure removes the plaque from inside the artery wall and restores the artery to normal. Recently, doctors specializing in the treatment of vascular problems started the use of balloon angioplasty and stent placement in the carotid arteries.
How is carotid ultrasound examination perfomed?
You will be asked to lie on your back. An ultrasound transmission non-staining gel and a probe will be placed on your neck.
How long does carotid ultrasound take?
The entire test lasts from 20 to 40 minutes, depending on the number of views, images and doppler velocity measurements.
Is special preparation for carotid ultrasound necessary?
No special preparation is necessary for this test.
Is it safe?
Carotid ultrasound is very safe. There are no risks from the ultrasound waves. Carotid ultrasound can be repeated many times without risks, complications or side effects related to the ultrasound imaging.
What are the benefits?
A major benefit of the carotid ultrasound is that it provides information about the carotid arteries and blood flow to the brain without entering the body. The information gained from the carotid ultrasound helps your doctor to make an accurate diagnosis and plan effective treatment that is best for you.
The results of the test will be reviewed and analyzed by a doctor after the test is performed. For the written results you may have to wait several days.