The amplitude is the signal height. The amplitude of the ultrasound echo is proportional to the difference of the acoustical impedance caused by different tissue layers. The amplitude decreases with increasing penetration depth of a homogeneous tissue.

See also Color Amplitude Imaging.

Amplitude map is a color Doppler display in which the color corresponds to the amplitude of the Doppler signal.

Amplitude shading is a method of reducing the side lobe levels in a transducer array. The shading usually causes the main beam to broaden by applying different voltages to the elements of the array.

See also Analog Output Signal.

The Doppler signal from any range gate is proportional to the number of red blood cells moving through during the periods of its read out, so the amplitude (or loudness) works as an indicator of the number of blood cell reflectors.
High Doppler amplitudes are generated by large pulsed Doppler or color Doppler imaging range gates and large vessels.

See also Amplitude Map, Color Amplitude Imaging.

(CAI) Color amplitude imaging shows the amplitude of the Doppler signal from moving blood flow. CAI is an ultrasound technique with increased dynamic range and flow sensitivity. The sensitivity of Doppler ultrasound increases markedly in conjunction with the use of vascular contrast agents.

See also Amplitude Map, Amplitude Indicator.