Ultrasound generally represents an umbrella term that includes common B-mode ultrasound, color ultrasound, and so on. Color ultrasound refers to the pseudo-color coding of the received signal after autocorrelation techniques based on multi-point selective Doppler to show the changes in blood flow, usually based on three basic colors: red, blue and green, with blood flow toward the probe generally designated as red and blood flow away from the probe designated as blue. Turbulence is usually indicated in green, and the brightness of red and blue is proportional to its corresponding blood flow velocity. Therefore, with color Doppler, the direction of blood flow, flow velocity and nature of blood flow can be displayed in real time. Most ultrasounds today are based on color ultrasound and then some other features are added.