![]() The change in frequency is related to the velocity of the moving red blood cells and can be measured to determine the velocity of the blood flow. When used to evaluate blood flow, sound waves increase in frequency when they echo from red blood cells moving toward the transducer and decrease in frequency when they move away from the transducer. For example, the pitch of a siren changes as an police car moves toward, past, and then away from the listener. The Doppler effect is a physics principle that states that relative to an observer, the frequency of any sound or light wave will vary as the source of the wave approaches or moves away. Images are produced by a computer using the frequency shift caused by the Doppler effect. Ultrasound waves used for medical imaging are usually in the range of 2 to 10 megahertz (MHz). A transducer is a hand-held device that converts electrical signals into ultrasound waves, directs the high-frequency sound waves to the artery or vein being tested, and then converts the returning ultrasound waves back into electrical signals. Descriptionĭoppler ultrasound testing is performed using an ultrasound scanner with Doppler imaging capabilities and a transducer. There is also no pain associated with Doppler ultrasound testing.Ĭigarette smoking may alter the results of the test, as nicotine can cause arteries in the extremities to constrict. Precautionsĭoppler ultrasonography is harmless, as it uses no ionizing (x ray) radiation. Other uses of the procedure include evaluation and diagnosis of tumors with vascular involvement, abdominal aortic aneurysms, heart valve defects and congenital heart disease. The test is done as an alternative to arteriography and venography, which are both invasive procedures with greater risks to the patient than Doppler ultrasound. ![]() The test can also be used to evaluate injuries to arteries such as damage due to myocardial infarction ( heart attack) or to monitor arterial reconstruction and bypass grafts. A Doppler study of blood flow can be used to diagnose many conditions, such as blood clots, incompetent valves in leg veins, which cause fluid to accumulate (venous insufficiency), deep vein thrombosis, a blocked artery (arterial occlusion), and narrowing (stenosis) of an artery. Purposeĭoppler ultrasonography is used to assess the direction, velocity, and turbulence of blood flow. In Doppler ultrasound, sound waves are transmitted through the body and are echoed back to produce images of blood flow in body tissues and organs. It uses high frequency sound waves that are above the level of human hearing (ultrasound). Doppler ultrasound, also called Doppler ultrasonography, is a noninvasive, painless procedure used to evaluate blood flow in major arteries and veins in the arms and legs.
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