Color Doppler
Doppler ultrasound and imaging are focused on the visualization and measurement of blood flow in the body. This is a technological achievement because, until recently, the received echoes from the acoustic scatterting from regions of blood, such as those in the chambers of the heart, were at levels so low that they could not be seen or appeared as black in an ultrasound image. Even when blood circulation, called color flow imaging, as well as precise continuous wave, and pulsed wave Doppler measurements of blood flow, are routine on imaging systems. In this specialized area of ultrasound, interrogating beams are sent repeatedly in the same direction and are compared to each other to determine the movement of blood scatterers over time. All the usual physics of ultrasound apply, including beam directivity, transducer bandwidth, absorption, and the scattering properties of the tissue (blood). Doppler detection is a blend of physics and specialized signal processing techniques required to extract, process, and display weak Doppler echoes. Doppler techniques provide critical diagnostic information noninvasively about the fluid dynamics of blood circulation and abnormalities.
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