Color Doppler ultrasound can display color blood flow information while displaying two-dimensional images of the exploration site. It has two manifestations: ① Color Doppler flow imaging (CDFl): extracting blood flow velocity parameters from Doppler and displaying blood flow images by using pseudo-color coding technology. Generally, the blood flow to the probe is set to red, and the blood flow away from the probe is set to blue. The brightness level of blood flow color is directly proportional to the blood flow velocity, that is, the faster the blood flow velocity, the brighter the brightness. These color blood flow images are superimposed on the two-dimensional and three-dimensional images displayed at the same time, and the direction, speed and nature of blood flow are judged by their colors and brightness, thus forming the actual color Doppler image ② Color Doppler energy map (CDE): imaging and color coding are carried out by using the signal intensity of Doppler, that is, the number of red blood cells passing through per unit area and the signal amplitude. Color indicates the existence of blood flow and brightness indicates the number of red blood cells.