Which statement accurately contrasts color Doppler and power Doppler in terms of velocity sensitivity and directional information?

• A. Color Doppler provides velocity and direction; power Doppler reflects signal strength (sensitivity to slow flow) without directional information.
• B. Color Doppler provides velocity magnitude only; power Doppler shows direction.
• C. Color Doppler shows direction only; power Doppler shows velocity and direction.
• D. Color Doppler shows velocity; power Doppler shows speed.

Answer: (A)

Understanding how these Doppler modes encode information helps. Color Doppler maps flow velocity by measuring the Doppler frequency shift and uses the sign of that shift to indicate direction: toward or away from the transducer. This means it provides both how fast the blood is moving and which way it’s going, usually shown with red and blue colors and sometimes a velocity scale.

Power Doppler, on the other hand, looks at the strength (amplitude) of the Doppler signal rather than the shift itself. This makes it much more sensitive to slow or weak flow and to small amounts of motion, but it discards the directional information, so you can’t tell whether the flow is toward or away from the transducer. The image shows flow presence and activity, not direction or exact speed.

So the correct statement captures that color Doppler provides velocity and direction, while power Doppler reflects signal strength with higher sensitivity to slow flow and without directional information. If you need to know direction and speed, use color Doppler; if you need to detect very subtle flow, use power Doppler.