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Doppler Ultrasound
About this test
A Doppler
ultrasound test uses reflected sound waves to see how
blood flows through a blood vessel. It helps doctors evaluate blood flow
through major arteries and veins, such as those of the arms, legs, and neck. It can show
blocked or reduced blood flow through narrowing in the major arteries of the
neck that could cause a
stroke. It also can reveal blood clots in leg veins
(deep vein thrombosis, or DVT) that could break loose
and block blood flow to the lungs (pulmonary embolism). See pictures of a
stroke 
and an
embolus . During pregnancy, Doppler ultrasound may be
used to look at blood flow in an unborn baby (fetus) to check
the health of the fetus.
During Doppler ultrasound, a handheld
instrument (transducer) is passed lightly over the skin above a blood vessel.
The transducer sends and receives sound waves that are amplified through a
microphone. The sound waves bounce off solid objects, including blood cells.
The movement of blood cells causes a change in pitch of the reflected sound
waves (called the Doppler effect). If there is no blood flow, the pitch does
not change. Information from the reflected sound waves can be processed by a
computer to provide graphs or pictures that represent the flow of blood through
the blood vessels. These graphs or pictures can be saved for future review or
evaluation. See a picture of a
Doppler ultrasound .
The four basic types of Doppler ultrasound are:
- "Bedside" or continuous wave Doppler. This type uses the change in pitch of the sound waves to provide information about blood flow through a blood vessel. The 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 be done at the bedside in the hospital with a portable machine to provide a fast estimate of the extent of blood vessel damage or disease.
- Duplex Doppler. Duplex Doppler ultrasound uses standard ultrasound methods to produce a picture of a blood vessel and the surrounding organs. Also, a computer converts the Doppler sounds into a graph that gives information about the speed and direction of blood flow through the blood vessel being evaluated.
- Color Doppler. Color Doppler uses standard ultrasound methods to produce a picture of a blood vessel. Also, 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 is a special type of color Doppler. Power Doppler can get some images that are hard or impossible to get using standard color Doppler. Power Doppler is most commonly used to evaluate blood flow through vessels within solid organs.
| By: | Healthwise Staff | Last Revised: December 4, 2010 |
| Medical Review: | Kathleen Romito, MD - Family Medicine Howard Schaff, MD - Diagnostic Radiology | |
© 1995-2011 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.
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