ARDMS (American Registry for Diagnostic Medical Sonography) Practice Test

When using spectral Doppler, the sonographer notices information correlates with that lower velocities missing from the waveform, what control can be modified to demonstrate these velocities?

1. Wall filter

2. Scale

3. Depth

4. Gain

The correct answer is: Wall filter

When using spectral Doppler, the sonographer can modify the wall filter control to demonstrate lower velocities that may be missing from the waveform. The wall filter is responsible for filtering out high-frequency Doppler shifts caused by the stationary tissues surrounding the blood vessel being imaged. By adjusting the wall filter setting to a lower level, it allows for the detection and display of lower-velocity flow information that may not be captured with a higher wall filter setting. In contrast, the scale control adjusts the range of velocities displayed on the spectral Doppler waveform, the depth control sets the imaging depth of the ultrasound beam, and the gain control adjusts the overall brightness of the image. While these controls are essential for optimizing the ultrasound image, they do not specifically address the issue of missing lower velocities in the waveform, which is why the correct answer is the wall filter control.