![]() ![]() ![]() Continuous-wave Doppler is the simplest mode.The health care worker then places the transducer on the area covered by gel and moves the device on the skin.ĭiagnostic information from the transducer is relayed in several ways: The health professional applies a water-soluble gel to the skin over the area to be scanned. The procedure begins with the patient being positioned for the scan. Exam length is based on factors such as the location of the area to be scanned and the difficulty in obtaining images. Flowing blood also makes a sound that can be heard with Doppler ultrasound.ĭoppler ultrasound tests usually take between 30 and 60 minutes. 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 a police car moves toward, past, and then away from the listener. Computer images may be preserved as recorded movement or as still pictures.ĭoppler ultrasound takes advantage of the Doppler effect, 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. These electrical signals can be converted into images by a computer. During this procedure, an instrument called a transducer converts electrical signals into ultrasound waves, directs the high-frequency sound waves to the vein being tested, and then converts the returning ultrasound waves that bounce off the body tissue back into electrical signals. Ultrasound waves used for medical imaging are usually in the range of 2 to 10 megahertz (MHz). Ultrasound is the medical use of sound waves with frequencies too high to be heard by humans. It is a safe procedure for pregnant women and does not affect cardiac pacemakers, metal implants or metal fragments lodged in the body.Īlthough the ultrasound test is not painful, the transducer is pressed on the skin and may cause discomfort in a patient already experiencing pain from conditions such as swollen limbs.Ĭigarette smoking may alter the results of the test, as nicotine can cause arteries in the extremities to constrict. Venous Doppler ultrasonography is harmless, as it uses no ionizing (x-ray) radiation, and there are no known harmful effects. Diagnostic Doppler ultrasound can also be performed on arteries (see arterial Doppler ultrasound). Venous Doppler ultrasound is done as an alternative to venography, which is an invasive procedures with greater risks to the patient than Doppler ultrasound. Doppler ultrasound can be used to evaluate and diagnose tumors with vascular involvement and aids in the placement of a catheter, a narrow tube placed in a blood vessel. This provides information about portions of damaged veins that may need to be removed. The test is also used to map a patient's veins. Varicose leg vein symptoms include swelling of the legs, twisted or enlarged leg veins, and leg discomfort. The Doppler exam is also used to diagnose varicose veins. This condition usually occurs in the legs and arms. Deep vein thrombosis is a condition caused when a clot develops in the large vein. These clots can cause thrombosis, which is the obstruction of blood flow through the blood vessel. A clot located in the heart or a blood vessel is a called a thrombus. A blood clot forms when blood changes from a flowing liquid into a solid mass. 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) or deep vein thrombosis. Venous Doppler ultrasound is used to assess the direction, velocity, and turbulence of blood flow through major veins in the patient's arms, legs, and neck. In Doppler ultrasound, these 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 (ultra sound). Venous Doppler ultrasound, also called sonography and ultrasonography, is a noninvasive, painless procedure used to evaluate blood flow in major veins in the arms and legs. ![]()
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