What does color Doppler estimate?

• A. Mean velocities at each spatial location
• B. Peak systolic velocity only
• C. Volume flow rate
• D. Tissue stiffness

Answer: (A)

Color Doppler maps Doppler shifts to color at each pixel, reflecting the average velocity of blood within that location along the ultrasound beam. The color magnitude corresponds to the mean velocity in that voxel, not a single instantaneous peak. Direction is shown by color toward or away from the transducer. This differs from spectral Doppler, which provides a velocity waveform with peak systolic velocity. Volume flow rate would require combining velocity with cross-sectional area, which color Doppler does not directly give. Tissue stiffness is assessed with elastography, not Doppler. So color Doppler estimates mean velocities at each spatial location.