Which method can help reduce aliasing when depth resolution is not required?

• A. Use CW Doppler
• B. Increase PRF
• C. Apply baseline shift
• D. Decrease depth

Answer: (A)

Aliasing in Doppler ultrasound comes from sampling velocity at a finite rate along depth in pulsed Doppler. When speeds exceed half of the PRF (the Nyquist limit), the measured velocity wraps around, causing aliasing. If depth resolution isn’t needed, continuous-wave Doppler is the best choice because it transmits and receives continuously along a line without relying on depth-specific sampling. Since there isn’t a discrete depth sample to wrap around, there’s effectively no aliasing, and very high velocities can be measured along the beam. The trade-off is loss of depth information—you only get velocity along the chosen line, with no range localization.