Do wall filters affect the accurate detection of spectral Doppler peak velocity?

• A. Yes, they always reduce peak velocity
• B. No, they mainly affect lower-velocity signals
• C. Yes, they distort peak velocity at high flow
• D. They only affect spectral broadening

Answer: (B)

Wall filters are designed to remove low-frequency Doppler shifts from tissue motion and very slow flow, effectively suppressing clutter near the baseline. This means they mainly affect signals at the low end of the velocity spectrum. The peak velocity in spectral Doppler comes from the highest Doppler shifts produced by the fastest-moving blood within the sample volume, which are not eliminated by a typical wall filter. Therefore, the wall filter does not generally distort the detection of spectral Doppler peak velocity. Only if the filter is set слишком aggressively might very slow-flow signals be suppressed, but the maximum velocity remains largely preserved.