The gain is a linear factor that is used in a device as a multiplier after calibration. The gain is the ratio of input to output in an amplifier. The sensitivity of a probe is adjusted by changing the gain.

See also Compress, and Reject.

(TGC) Time gain compensation is the signal processing control that allows the sonographer to amplify the returning signal from deeper structures in the body. The TGC control compensates for the attenuation of sound waves.

(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.

(ADC) A system that receives analog input data and produces digital values at its output. Analog to digital converters are used by the ultrasound scanner to convert the received signal into a format more compatible with the computer systems.
Ultrasound front-end-systems as well as many others sophisticated electronic systems use these analog signal processing components in connection with e.g., low-noise amplifier (LNA), and time gain compensation amplifier (TGC) as key elements in determining the overall system performance.

See also Digital to Analog Converter, and Digitization.

Compress is a signal processing control on some ultrasound systems that affects the gray scale and overall gain.