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Power Doppler is a highly sensitive medical test that detects the flow of blood through arteries. During a Doppler ultrasound, a specific area of the body is covered in a special Doppler gel, and an instrument called a transducer is placed over the area. Sound waves are sent into the body and are deflected off organs and blood cells, and they are then picked up by a microphone and sent to a computer for analysis. Physicians can then detect blockages in arteries in the abdomen, chest, head and neck as well as in the arms and legs. The test also is used to check on the health of developing fetuses.
Regular or irregular patterns of blood flow change the sounds that are heard coming from the power Doppler equipment. It is up to five times more sensitive than color Doppler ultrasound and can provide a picture of blood flow within organs. The images also can be amplified to a higher degree because there is less interfering noise that can distort the picture after it is processed. It is this characteristic in flow sensitivity that makes power Doppler so beneficial.
Power Doppler does not indicate how fast or in what direction blood is moving within specific blood vessels. Although it is not sensitive to disturbances in the image because of signal amplification, the movement of soft tissues in the body can cause interference. There are additional systems that detect these motions and can cancel them out of the Doppler imaging results.
Blockages in arteries and veins, such as plaque and clots, can be detected using power Doppler. The Doppler test is also useful in showing how well blood flows back to the heart and to the brain. It also is able to show whether blood is flowing normally within transplanted organs. A high-pitched or turbulent sound occurs when an abnormality such as a blockage is detected, and something that is disrupting blood flow can be seen as color variations on the computer screen.
Despite its ability to detect major problems, power Doppler is not an uncomfortable procedure. Cold from the gel is the only sensation felt, unless blood pressure cuffs are used, which can create a feeling of pressure. The procedure is completely safe and carries no risk in damaging organs or harming fetuses, and the results are attained relatively quickly to detect conditions that might be significant.