Which artifact is a mirror of the true waveform across the baseline due to aliasing?

Which artifact is a mirror of the true waveform across the baseline due to aliasing?

• A. Aliasing
• B. Mirror image
• C. Bidirectional flow
• D. Spectral broadening

Answer: (B)

When the Doppler sampling frequency (PRF) isn’t high enough to capture the true velocity shifts, the spectrum wraps around at the Nyquist limit. Velocities that should appear on one side of zero velocity show up on the opposite side, creating a reflected copy of the waveform across the baseline. This mirrored appearance is the artifact produced by aliasing. It’s different from spectral broadening (which is a wide range of velocities rendering a broader spectrum), and from bidirectional flow (which describes flow direction, not an imaging artifact).

When the Doppler sampling frequency (PRF) isn’t high enough to capture the true velocity shifts, the spectrum wraps around at the Nyquist limit. Velocities that should appear on one side of zero velocity show up on the opposite side, creating a reflected copy of the waveform across the baseline. This mirrored appearance is the artifact produced by aliasing. It’s different from spectral broadening (which is a wide range of velocities rendering a broader spectrum), and from bidirectional flow (which describes flow direction, not an imaging artifact).