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An imaging technique using ultrasound that can detect moving liquids.
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that in which measurement and a visual record are made of the shift in frequency of a continuous ultrasonic wave proportional to the blood-flow velocity in underlying vessels; used in diagnosis of extracranial occlusive vascular disease. It is also used in detection of the fetal heartbeat or of the velocity of movement of a structure, such as the beating heart.
color flow Doppler ultrasound
a form of pulse wave Doppler in which the energy of the returning echoes is displayed as an assigned color; by convention echoes representing flow towards the transducer are seen as shades of red, and those representing flow away from the transducer are seen as shades of blue. The color display is usually superimposed on the B-mode image, thus allowing simultaneous visualization of anatomy and flow dynamics.
continuous wave Doppler ultrasound
a technique in which the transducer emits and receives the ultrasound beam continuously, enabling the measurement of high velocity blood flow, such as occurs through heart valve stenoses.
duplex Doppler ultrasound
a form of image display in which both spectral and color flow images are seen simultaneously. This facilitates accurate anatomical location of the blood flow under investigation.
Doppler ultrasound flowmeter
a device for measuring blood flow that transmits sound at a frequency of several megahertz downstream along the flowing blood. Some of the sound waves are reflected by the moving red blood cells back toward the transducer. The difference in pitch between the transmitted and reflected sounds is produced as an audible tone and is proportional to the velocity of blood flow. The flowmeter can be incorporated into a stethoscope so that qualitative and quantitative measurements of the flow of blood through arteries and veins can be obtained. The Doppler flowmeter is capable of recording very rapid pulsatile changes in flow as well as steady flow.
pulse wave Doppler ultrasound
a technique in which the transducer emits ultrasound in pulses. Blood flow velocities so measured are limited to around the physiologic range (up to approximately 1.5 meters/second) but the depth from which the returning echoes originate can be accurately determined.
spectral Doppler ultrasound
a form of ultrasound image display in which the spectrum of flow velocities is represented graphically on the Y-axis and time on the X-axis; both pulse wave and continuous wave Doppler are displayed in this way.