(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.

(DCPD) Directional color power Doppler combines power (amplitude) of Doppler signal with directional (phase) information to encode direction and variations in blood flow. DCPD is used in analysis of blood flow to assess blood vessel or vascular function.

See also Color Power Doppler, Quadrature Detection, and Directional Indicators.

Doppler ultrasound is a medical imaging technique for calculating the relative velocity between two points by measuring the frequency shift of a sound wave transmitted from one point to the other, based on the Doppler effect. Continuous or pulsed Doppler is frequently used to examine cardiovascular blood flow. The combination of routine 2D-mode and Doppler ultrasound allows a complete evaluation of the heart's anatomy and function (including the fetal heart). See also Doppler Fluximetry in Pregnancy.
Doppler ultrasound depends on the fact that if a moving object reflects the ultrasound waves, the echo frequencies are changed. A higher frequency is created if the object is moving toward the probe//transducer and a lower frequency if it is moving away from it. How much the frequency is changed depends upon how fast the object is moving. Doppler ultrasound shows the different rates of blood flow in different colors on a monitor in real time.
The major Doppler parameters are the peak systolic velocity and the end-diastolic velocity. The peak systolic velocity ratio compensates the variability between different patients and instrumentations.

Different Doppler and duplex techniques:

(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.

(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.