(CCI) A major limitation of the use of ultrasound contrast agents is the problem that signals from the microbubbles are mixed with those from tissue, so that the distribution of the microbubbles is not optimally displayed either in Doppler or gray scale.
Coherent contrast imaging is a high frame rate implementation of inverting the phase of alternate sound pulses and summing the resulting echoes. The symmetrical signals from linear reflectors are cancelled leaving those from non-linear scatterers, with the advantage that the cancellation is performed without the need to transmit two pulses per image line so that bubble destruction is minimized. Coherent contrast imaging yields best results in the vascular phase of phospholipid microbubbles (such as Definity and SonoVue).

See also Coherence.

(CD) Color Doppler is an ultrasound imaging mode, which visualizes the presence, direction and velocity of flowing blood in a wide range of flow conditions. It provides an estimate of the mean velocity of flow within a vessel by color coding the flow and displaying it superimposed on the 2D gray scale image. The flow direction is arbitrarily assigned the color red or blue, indicating flow toward or away from the transducer.
Color (colour, Brit.) Doppler ultrasound is capable of evaluating a wider area than other Doppler modes than for example Duplex or power Doppler, and therefore makes it less likely to miss flow abnormalities. It is also easier to interpret. Color flow is not as precise as conventional Doppler and is best used to scan a larger area and then use conventional Doppler for detailed analysis at a site of potential flow abnormality.

Adjustments for color Doppler in case of too much color:
Adjustments for color Doppler in case of not enough color:
See also Color Power Doppler, Autocorrelation, Color Priority, Triplex Exam and Color Saturation.

(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.