Increased Sweep Speed: This affects the display of the waveform over time but does not impact the appearance of the spectral Doppler signal in the way shown.
Decreased Pulse Repetition Frequency (PRF): Lowering the PRF can lead to aliasing, which is evident as the waveform wrapping around in the spectral display from image A to image B. This makes the velocity appear higher than it actually is.
Decreased Wall Filter: This adjustment primarily affects the elimination of low-frequency Doppler signals but does not typically cause the kind of changes seen in the images.
Increased Spectral Gain: Increasing the gain would result in a brighter spectral display but not the wrapping of the signal as seen.
Reference:
"Understanding Ultrasound Physics" by Sidney K. Edelman
ARDMS Sonography Principles and Instrumentation study materials