Power Doppler encodes color based on which property?

• A. Amplitude of the Doppler signal
• B. Frequency shift
• C. Phase shift
• D. Velocity

Answer: (A)

Power Doppler encodes color based on the amplitude (power) of the Doppler signal. The color intensity on the display reflects how strong the Doppler signal from moving red blood cells is, which increases with the amount of moving blood and the scatter from those cells. Because it's driven by signal power rather than the actual frequency shift, Power Doppler is more sensitive to slow flow and is relatively angle-insensitive, but it does not provide information about flow direction or exact velocity. This makes it particularly useful for detecting vascularity and perfusion in areas where conventional color Doppler might miss flow.