(CDI) Color Doppler imaging depicts the mean frequency shifts of the Doppler signal. Color [colour, Brit.] Doppler imaging is a method for visualizing direction and velocity of movement, such as of blood flow within the cardiac chambers or blood vessels. The flow direction and velocity information gathered by Doppler ultrasonography is color coded onto a gray scale cross-sectional image. The sensitivity of Doppler ultrasound is increased in conjunction with the use of vascular contrast agents.
Direction and blood flow velocity are coded as colors and shades:
Red - flow coming nearer to the probe.
Blue - flow coming away of the probe.

See also Bi-directional Illumination, Color Map.

(CFI) Color flow imaging is based on pulsed ultrasound Doppler technology. With this technique multiple sample volumes among multiple planes are detected and a color map for direction and velocity flow data is displayed.
Common mapping formats are BART (Blue Away, Red Towards) or RABT (Red Away, Blue Towards). Enhanced or variance flow maps show saturations and intensities that indicate higher velocities and turbulence or acceleration. Some maps utilize a third color (green) to indicate accelerating velocities and turbulence.
Color flow Doppler imaging is not as precise as conventional Doppler and is best used to scan a larger area and then use other Doppler modes to obtain more precise data.

See also Color Amplitude Imaging, Color Priority, and Color Saturation.

In a color map, colors are allocated to Doppler shift frequencies corresponding to flow. Color (colour, Brit.) maps may also display Doppler amplitude, signal power, variance, or the gray levels of the B-mode image.

See also Color Amplitude Imaging, Color Priority, and Color Saturation.

(CPA) Color power angio is a Doppler measurement, which employs the Doppler effect to assess whether blood is moving towards or away from the probe. By calculating the frequency shift of a particular sample volume, its speed and direction can be determined and visualized. This is particularly useful in cardiovascular studies and essential in many areas such as determining reverse blood flow in the liver vasculature in portal hypertension. The CPA information is displayed as a color image superimposed on the 2D gray scale image.

See also Color Power Doppler.

(CPD) CPD is a type of color Doppler to visualize the presence of detectable blood flow. The flow information is based on the amplitude or strength of echoes received from moving cells and not on frequency shifts. Power Doppler is very sensitive to flowing blood but does not provide velocity or directional information.
CPD is less angle dependent than traditional color Doppler, but more sensitive to motion artifacts. Color power angio (CPA) provides better sensitivity to slow flow states.
The color maps for CPD are represented by a single continuous color (colour, Brit.). Because CPD does not provide directional information, no aliasing artifact occurs.

See also Directional Color Power Doppler.