(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.

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Digital systems use discrete numerical values or non-numeric symbols for input, processing, transmission, storage, or display rather than being composed of variable voltage, acoustic field or electromagnetic field.

See also Digital Imaging and Communications in Medicine and Analog to Digital Converter.

Process of conversion of continuous (analog) signals, such as the detected ultrasound or MRI signal (voltage), into numbers. This is carried out with an analog to digital converter.
There are two kinds of discretization involved: the voltage is only measured (sampled) at particular discrete times and only voltages within a particular range and separated by a particular minimum amount can be distinguished. Voltages beyond this range are said to exceed the dynamic range of the digitizer.