Which parameter encodes velocity in color Doppler display?

Which parameter encodes velocity in color Doppler display?

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

Answer: (D)

In color Doppler, velocity is encoded by the Doppler frequency shift. As blood cells move toward or away from the transducer, their motion causes a change in the reflected frequency that is proportional to the velocity component along the beam. This Doppler shift is what the color map uses to determine both the direction (toward or away) and the magnitude (how fast) of flow. The color hue indicates direction, while the brightness or saturation reflects the size of the shift, i.e., the velocity. Amplitude and power describe the strength of the returned signal, not the speed of flow, and thus do not encode velocity. The frequency shift is the actual measure tied to motion, so it is the parameter that carries velocity information.

In color Doppler, velocity is encoded by the Doppler frequency shift. As blood cells move toward or away from the transducer, their motion causes a change in the reflected frequency that is proportional to the velocity component along the beam. This Doppler shift is what the color map uses to determine both the direction (toward or away) and the magnitude (how fast) of flow. The color hue indicates direction, while the brightness or saturation reflects the size of the shift, i.e., the velocity.

Amplitude and power describe the strength of the returned signal, not the speed of flow, and thus do not encode velocity. The frequency shift is the actual measure tied to motion, so it is the parameter that carries velocity information.