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Doppler Ultrasound for Detecting DVT

A Doppler ultrasound is often the procedure of choice for detecting deep vein thrombosis (DVT). This test uses reflected sound waves to show doctors how blood is flowing through veins and arteries. It is very effective in detecting clots.

DVT is extremely difficult to detect because its symptoms are similar to those of many other physical conditions. Doppler ultrasounds allow doctors to see how fast blood is flowing in veins and arteries, thus helping them to determine if a patient actually has DVT.

A Doppler ultrasound is very accurate in detecting clots above the knee, which can develop into pulmonary embolisms.

Doppler Ultrasound Procedure

Doppler ultrasounds are usually performed on an outpatient basis, either in a physician's office or a hospital diagnostic facility. The procedure itself takes 30 to 45 minutes for most patients.

Here are the basic steps involved in a Doppler ultrasound:

First, a blood pressure cuff is wrapped around the ankle.
Next, a transducer with gel on it is placed over pulse points on the foot and lower leg. High-frequency sound waves are bounced off the soft tissue. The echoes are converted into images on a monitor.
The doctor looks at the images in order to examine the blood vessels and make a diagnosis.

Types of Doppler Ultrasound

There are several types of Doppler ultrasound, including:

Color Doppler ultrasound uses standard ultrasound methods to produce a picture of a blood vessel. Next, a computer converts the Doppler echoes into colors and overlays them on the image of the blood vessel. This helps show the speed and direction of blood flow through the vessel.
Pulsed Doppler ultrasound allows a doctor to measure the velocity of blood in a sampling volume.
Power Doppler ultrasound shows the amplitude (power) of Doppler signals. This helps doctors detect a larger range of Doppler shifts. The result is better visualization of small vessels.

Other Procedures for Detecting DVT

There are other tests that a doctor can perform to detect DVT, including:

Impedance plethysmography is conducted by placing two sets of electrodes around the patient's calf and an oversized blood pressure cuff around the thigh. The electrodes sense a change in blood volume in the calf veins, which is recorded on a strip chart. This test may detect extensive calf vein thrombosis.
Venography shows the flow of blood. During the test, a doctor injects a special dye that can be seen in X-rays into the veins. An X-ray is then taken to reveal the blood-flow images.

Venography is a very accurate test. However, it is not used often because it can be painful and expensive and exposes the patient to radiation. Venography can also trigger reactions and complications in people who are allergic to the dye that is used during the test.
Venous duplex ultrasound uses high-frequency ultrasound to analyze blood flow inside veins in the arms and legs.

Despite these tests, Doppler ultrasound remains the preferred diagnostic technique for DVT due to its track record of precision and accuracy.

Resources

Answers.com (2007). Deep Vein Thrombosis. Retrieved July 23, 2007, from the Answers.com Web site:
http://www.answers.com/topic/what-is-the-doppler-effect.

De Milto, Lori (1999). Deep vein thrombosis. Retrieved July 23, 2007, from the LookSmart Find Articles Web site:
http://findarticles.com/p/articles/mi_g2601/is_0004/
ai_2601000408.

Flight Health (n.d.) How to Spot Deep Vein Thrombosis (DVT). Retrieved July 23, 2007, from the FlightHealth.org Web site: http://www.flighthealth.org/how-to-spot-dvt.htm.

Hirsch, Jack; Hoak, John. (1996). Management of Deep Vein Thrombosis and Pulmonary Embolism. Retrieved July 23, 2007, from the American Heart Association Web site:
http://circ.ahajournals.org/cgi/content/full/93/12/2212.

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