Power Doppler compared to Color Doppler: which statement is true?

• A. It encodes signal strength and is more sensitive to low flow but lacks direction/velocity.
• B. It encodes velocity and direction.
• C. It has higher frame rate.
• D. It provides velocity vectors.

Answer: (A)

Power Doppler operates on Doppler energy—the strength of the Doppler signal—rather than on the actual Doppler shift. This means the color intensity reflects how much moving blood signal there is, not how fast or in which direction the blood is moving. Because it detects signal power, it is much more sensitive to detecting low-flow or tenuous blood signals, which is why it often reveals flow that velocity-based color Doppler might miss. The trade-off is that no velocity or direction information is encoded, so you can’t determine how fast the flow is or which direction it’s going, nor can you construct velocity vectors. In contrast, Color Doppler specifically encodes velocity and direction, which is why the true statement about Power Doppler is that it encodes signal strength, is more sensitive to low flow, but lacks direction/velocity information.