The analog output signal is voltage output corresponding to the parameter measured by a device. The produced signal is calibrated by a scaling factor.

(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.

Anechoic areas are regions without internal echoes (echo free). Cysts or fluid filled regions are anechoic and may demonstrate enhanced echoes posterior to the fluid.

Angiography means the imaging of veins and arteries. Without the need of X-rays, vessels and their surrounding tissue can be depicted with different methods including Doppler techniques to measure blood flow.

(Doppler look angle) The angle of incidence is the angle at which the ultrasound beam strikes an interface, or the angle at which the Doppler beam intersects the blood flow. Doppler signals are best obtained at angles of 60° or less.

See also Snells Law.