Which statement is true about the wall filter?

Which statement is true about the wall filter?

• A. It eliminates frequencies above a threshold
• B. It eliminates frequencies below a threshold
• C. It enhances high-frequency components
• D. It suppresses lateral resolution

Answer: (B)

Wall filter works as a high-pass filter for the Doppler signal, aiming to remove clutter from tissue motion and vessel walls that produce low-frequency shifts. By setting a cutoff frequency, signals below that threshold are attenuated while higher-frequency Doppler shifts from moving blood pass through. That’s why the true statement is that it eliminates frequencies below a threshold. The other ideas would misrepresent its function: removing frequencies above a threshold would discard useful flow information, claiming it enhances high-frequency components implies boosting amplitude rather than suppressing, and saying it suppresses lateral resolution isn’t accurate since the filter mainly shapes the spectral content rather than the image’s spatial resolution.

Wall filter works as a high-pass filter for the Doppler signal, aiming to remove clutter from tissue motion and vessel walls that produce low-frequency shifts. By setting a cutoff frequency, signals below that threshold are attenuated while higher-frequency Doppler shifts from moving blood pass through. That’s why the true statement is that it eliminates frequencies below a threshold. The other ideas would misrepresent its function: removing frequencies above a threshold would discard useful flow information, claiming it enhances high-frequency components implies boosting amplitude rather than suppressing, and saying it suppresses lateral resolution isn’t accurate since the filter mainly shapes the spectral content rather than the image’s spatial resolution.