Which Doppler technique is used to measure high velocities with reduced aliasing?

• A. High-PRF Doppler
• B. Power Doppler
• C. Spectral Doppler
• D. Angle Doppler

Answer: (A)

Aliasing in Doppler imaging happens when the velocity Doppler shift being measured exceeds the Nyquist limit set by the pulse repetition frequency. If you want to measure higher velocities without wrap-around, you raise the PRF, which raises the Nyquist limit. High-PRF Doppler uses a higher pulse repetition frequency, expanding the range of velocities that can be measured without aliasing. That makes it the best choice when the goal is to quantify fast flow with reduced aliasing.

Power Doppler increases sensitivity to flow but does not provide velocity information, so aliasing isn’t a factor there. Spectral Doppler can show aliasing if velocities exceed the current scale, and you’d typically adjust settings to manage it rather than inherently avoiding it. Angle Doppler focuses on correcting velocity calculations for the line-of-sight angle and doesn’t by itself prevent aliasing.