Doppler Ultrasound

A Doppler ultrasound is a type of ultrasound imaging test that uses sound waves to show how well your blood flows through your blood vessels. It can be used to examine blood flow in many parts of your body, including many of your organs and your neck, arms, and legs. A Doppler ultrasound can examine your arteries (blood vessels that carry oxygen-rich blood from your heart and lungs to your body) and veins (blood vessels that carry blood from your body back to your heart and lungs to get more oxygen).

Doppler ultrasound works by bouncing sound waves off red blood cells flowing through your blood vessels. The ultrasound device measures the echoes that bounce back from the cells. Cells that are moving away from the sound waves make different echoes than cells that are moving closer to the sound waves.

This is called the Doppler effect, named after the scientist who discovered it. Doppler ultrasound can check for blood vessel conditions that affect the amount, speed, and direction of blood flow in different parts of your body. It can help find narrowed arteries, blood clots, and other conditions.

There are different types of Doppler ultrasound tests that can be used to gather different information. They include: Color Doppler. This test uses a computer to change sound wave measurements into different colors.

The colors show the speed and direction of blood flow.; Power Doppler. This is a newer type of color Doppler. It can show much smaller blood vessels and slower blood flow than standard color Doppler.

But it can't show the direction of blood flow.; Spectral Doppler. This test shows blood flow information in a graph. It can show how much of a blood vessel is blocked.

There are two types of spectral Doppler ultrasound: A 'pulsed wave' Doppler can show where blood is flowing at different speeds, but it can't record blood flowing at high speeds.; A 'continuous wave' Doppler can record very fast blood flow, but it can't show the exact location in the blood vessel.; ; Duplex Doppler. This test uses standard ultrasound to take images showing blood flow. Then a computer turns the images into a graph, as in spectral Doppler.;

Why this test is done

You may need a Doppler ultrasound if you have symptoms of abnormal blood flow. Your symptoms will depend on the part of your body that's affected and the cause of abnormal blood flow.

You may also need a Doppler ultrasound if you:

• Have a high risk of having a stroke or have had a stroke or a transient ischemic attack (a stroke that lasts a few minutes). An ultrasound of your brain, called a transcranial Doppler ultrasound, can diagnose the cause of a stroke and/or help estimate your risk for having a stroke in the future.
• Had an injury to your blood vessels.
• Have high blood pressure that could be caused by blocked arteries in your kidneys.
• Are being treated for a condition that affects blood flow. A Doppler ultrasound can show how much the treatment is helping.
• Are pregnant. You may need this test if your unborn baby may be smaller than normal for your stage of pregnancy. You may also need this test if you have certain health problems such as high blood pressure in pregnancy (preeclampsia) or sickle cell disease.

How to prepare

Preparations for a Doppler ultrasound depend on what part of your body is being checked. Your health care provider will tell you if you need to prepare and what to do. You may need to:

• Fast (not eat or drink) for several hours before the test.
• Stop smoking or using products that have nicotine for two hours or more before your test. Nicotine causes blood vessels to narrow, which could change your results.

Sample type

Blood

Other names for this test

Doppler ultrasonography, vascular ultrasound