What Is Doppler Ultrasound?
Doppler ultrasound is a special form of ultrasound commonly used to evaluate blood flow. It can be displayed in variable formats: an audible sound, a spectrum of colors within blood vessels, or a graph showing changes in velocity.
There are several types of Doppler ultrasound in use:
Continuous Wave Doppler Ultrasound
This type of Doppler ultrasound uses the change in pitch of the sound waves to provide information about blood flow through a blood vessel.
Your doctor listens to the sounds produced by the transducer to evaluate the blood flow through an area that may be blocked or narrowed. This type of ultrasound can provide a rapid estimate of the extent of blood vessel damage or disease.
Duplex Doppler Ultrasound
Duplex Doppler ultrasound uses standard ultrasound methods to produce a picture of a blood vessel and surrounding organs.
In addition, a computer converts the Doppler sounds into a graph that provides information about the speed and direction of blood flow through the blood vessel being evaluated. With this type of Doppler ultrasound, it is possible to see the structures inside the body (2D) and evaluate blood flow (continuous wave) within those structures at the same time.
To do this, the ultrasound machine uses the 2 methods of ultrasound simultaneously. Blood flow in individual blood vessels is most commonly evaluated by duplex Doppler ultrasound.
Color Doppler Ultrasound Color Doppler ultrasound uses standard ultrasound methods to produce a picture of a blood vessel (2D). In addition, a computer converts the Doppler sounds into colors that are overlaid on the image of the blood vessel and that represent the speed and direction of blood flow through the vessel.
Power Doppler Ultrasound
Power Doppler ultrasound is a new ultrasound technique that is up to 5 times more sensitive than color Doppler ultrasound.
Power Doppler ultrasound can also obtain some images that are difficult or impossible to obtain using standard color Doppler ultrasound. However, power Doppler ultrasound is used most commonly to evaluate blood flow through vessels within organs, such as the liver or kidneys.
Why Should I Have a Doppler Ultrasound Exam?
A Doppler ultrasound exam, often called a scan, gives your doctor a great deal of information about your blood vessels and about the way blood is passing through them. Doppler ultrasound is particularly well suited to evaluating problems within your veins and arteries. Because we have blood vessels throughout our bodies, Doppler ultrasound may be used almost anywhere. Some of the most common sites where Doppler ultrasound is used are in the neck, heart, abdomen, and legs. In your neck, Doppler ultrasound is used to look at carotid arteries. These vessels supply large amounts of blood to your brain and may become blocked. Blockage can lead to stroke. In your heart, Doppler ultrasound can tell your doctor about the flow of blood and whether it is directed correctly. In your abdomen or stomach, Doppler ultrasound can be used to help evaluate blood flow to the liver and many other organs in your abdomen. Doppler ultrasound also is used to evaluate blood flow in your legs and may be helpful in identifying blockages in your arteries and clots in your veins.
What Can I Expect During the Exam?
The images made by the returning echoes are displayed on a monitor, which look likes a small television screen. In addition, returning sound waves that have been reflected by moving blood can be heard by means of speakers in the instrument.
The sounds may be similar to the sound of wind blowing through the trees. The room is usually darkened during the examination to make it easier for the sonographer or doctor to see the images on the monitor.
How Long Will the Exam Take?
The average Doppler ultrasound exam takes 30 to 60 minutes. The length of the exam depends on numerous factors including the portion of your body to be examined and the complexity of the anatomy.
With arteriosclerosis, or hardening of the arteries, the vessels may be very difficult to evaluate and may require more scanning time.
Who Will Perform the Exam?
A Doppler ultrasound examination may be performed by a doctor, or by a vascular technologist or sonographer – individuals specially trained to perform ultrasound exams. A doctor will interpret the examination results.
Will I Need More Than One Exam?
In many cases, follow-up exams are necessary to evaluate the progress of your condition or your response to therapy. Excerpt from the Medical Ultrasound Fact Sheet from the American Institute of Ultrasound in Medicine (AIUM)