Figure 8b. (a) Concept of color flow imaging. In this mode, the US instrument launches interrogating pulses for lines within a region of interest. For each line, the mean Doppler shift is determined for a series of locations along the beam axis. (b) Color flow image shows flow in a vessel of a Doppler phantom. Mean velocities within a pixel are represented in color; a color scale on the image provides the velocity range depicted. These velocities are not corrected for the Doppler angle.