To avoid aliasing in Doppler imaging, which adjustment would help?

To avoid aliasing in Doppler imaging, which adjustment would help?

• A. Increase wall filter
• B. Increase pulse repetition frequency
• C. Decrease color gain
• D. Change color map

Answer: (B)

Aliasing in Doppler imaging happens when the Doppler signal is sampled too slowly, so velocities higher than half the pulse repetition frequency (the Nyquist limit) wrap around. Increasing the pulse repetition frequency raises that limit, letting faster blood velocities be represented without wrap-around and thus reducing aliasing. Keep in mind that raising PRF can limit depth visibility due to range ambiguity, so it’s a balance. The other adjustments don’t address the sampling limit: wall filter targets low-frequency tissue motion, not aliasing; color gain affects brightness; changing the color map changes appearance but not the sampling or aliasing behavior.

Aliasing in Doppler imaging happens when the Doppler signal is sampled too slowly, so velocities higher than half the pulse repetition frequency (the Nyquist limit) wrap around. Increasing the pulse repetition frequency raises that limit, letting faster blood velocities be represented without wrap-around and thus reducing aliasing. Keep in mind that raising PRF can limit depth visibility due to range ambiguity, so it’s a balance. The other adjustments don’t address the sampling limit: wall filter targets low-frequency tissue motion, not aliasing; color gain affects brightness; changing the color map changes appearance but not the sampling or aliasing behavior.