What aspect of the Doppler spectrum is color-encoded with color Doppler?

• A. Amplitude
• B. Frequency shift
• C. Power
• D. Velocity

Answer: (B)

Color Doppler maps how fast blood is moving and in what direction onto colors on the image. The Doppler shift you measure is tied to velocity, and the display uses that velocity (including toward or away from the transducer) to assign colors. So the color-encoded aspect is the flow velocity. The other ideas—amplitude, raw frequency shift, or power—are related to different measurements: amplitude corresponds to signal brightness, frequency shift is the underlying physical quantity that relates to velocity but isn’t itself what the color map shows, and power Doppler represents signal strength rather than velocity.