To suppress low-velocity components while preserving higher-velocity signals, which setting would you adjust?

To suppress low-velocity components while preserving higher-velocity signals, which setting would you adjust?

• A. Increase PRF
• B. Increase gain
• C. Increase wall filter
• D. Decrease wall filter

Answer: (C)

The setting being tested is the wall filter, which acts as a high-pass filter on the Doppler signal. By raising the wall-filter cutoff, you push out the low-frequency components caused by tissue motion and very slow flow, which suppresses low-velocity signals. The faster, higher-velocity blood flow has higher Doppler frequencies and stays in the passband, so those signals are preserved. If you lower the wall filter, you’ll allow more low-velocity (and tissue) signals to appear, which isn’t desired here. The other options don’t selectively target velocity ranges: increasing PRF changes aliasing and the maximum detectable velocity; increasing gain amplifies all signals including noise; decreasing the wall filter would reduce suppression of slow components.

The setting being tested is the wall filter, which acts as a high-pass filter on the Doppler signal. By raising the wall-filter cutoff, you push out the low-frequency components caused by tissue motion and very slow flow, which suppresses low-velocity signals. The faster, higher-velocity blood flow has higher Doppler frequencies and stays in the passband, so those signals are preserved.

If you lower the wall filter, you’ll allow more low-velocity (and tissue) signals to appear, which isn’t desired here. The other options don’t selectively target velocity ranges: increasing PRF changes aliasing and the maximum detectable velocity; increasing gain amplifies all signals including noise; decreasing the wall filter would reduce suppression of slow components.