Which Doppler modality displays velocity information over a region rather than a single depth?

• A. Pulsed wave Doppler
• B. Continuous wave Doppler
• C. Color Doppler imaging
• D. Power Doppler

Answer: (C)

Velocity information across a region is displayed by color Doppler imaging. It encodes Doppler shifts as colors for every pixel in the two-dimensional image, so you see a velocity field throughout the scanned area rather than at just one depth. This regional display comes from evaluating Doppler shifts across many depths and lateral positions within the image, producing a map of how fast and in what direction blood is moving at each point.

Pulsed wave Doppler, by contrast, samples a single depth—the range gate—and provides a spectral waveform over time at that specific location. Continuous wave Doppler analyzes Doppler shifts along the entire beam path but lacks depth resolution, so it doesn’t create a region-wide velocity map. Power Doppler shows the presence and strength of flow but not the velocity values or direction.