In color Doppler, the Doppler frequency shift is conveyed by which type of encoding?

• A. Velocity-encoded
• B. Phase-encoded
• C. Amplitude-encoded
• D. Color-encoded

Answer: (D)

Color Doppler communicates Doppler frequency shifts by mapping velocity information into color on the image. The system converts the frequency shift, which relates to flow speed, into a color value on a map that shows direction and speed of flow. Typically, flow toward the transducer is shown in one color (often red) and flow away in another (often blue), with brightness or saturation indicating how fast the flow is. This visual encoding lets you assess both the direction and the relative speed of blood flow directly on the anatomical image. Other encoding schemes would display velocity differently (for example as a spectral waveform), but color Doppler uses color encoding to convey the Doppler shifts.