The purpose of this review is to help in understanding the principles
of a new ultrasound Doppler technique called amplitude-coded colour Do
ppler (power) mode, All pertinent information available in the literat
ure on the physical principles of this technique has been revised in o
rder to give a detailed survey. The main components and the key charac
teristics of this mode are discussed together with illustrative exampl
es. In addition, work-in-progress developments and other future aspect
s of US imaging in combination with this technique are discussed.