(CPU) The CPU is the brain of the ultrasound machine, the main processor in the computer.
The CPU executes complex computer programs to send electrical currents to the transducer probe to emit sound waves, to receive the electrical pulses from the probes that were created from the returning echoes. The CPU does the calculations, data processing and forms the image on the display. The CPU also stores the processed data and/or image on disk.disk.

Clutters are unwanted components of the received signal. In contrast enhanced ultrasound, clutter often describes the part of the received echo that is not from microbubble contrast agents.

See also Release Burst Imaging.

(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.

(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.

The color priority determines which signal of B-mode and Doppler, detected from the same location will be displayed in a given pixel. Low color priorities will allow solid tissue to conceal Doppler shifts at the same location; a high priority ensures that color will overwrite the gray scale image.
Also called color-echo write priority or angio write priority.

See also Directional Indicators.