During carotid duplex ultrasonography, a high-velocity jet at a stenosis is displayed with its peak wrapped around to the opposite side of the spectral baseline, so that the true peak velocity cannot be measured. Which adjustment will BEST correct this finding?

• A Decrease the wall filter
• B Increase the sample volume size
• C Decrease the transmit frequency while keeping the angle constant
• D Increase the pulse repetition frequency (scale) ✓

Explanation

Aliasing occurs when the Doppler shift exceeds half the pulse repetition frequency (the Nyquist limit), so the peak folds across the baseline. Raising the PRF raises the Nyquist limit and unwraps the spectrum; baseline shifting is another accepted fix. Decreasing the wall filter removes low-frequency clutter but does not affect the Nyquist limit. A larger sample volume worsens spectral broadening rather than correcting wrap-around.

Reference: Rumack Diagnostic Ultrasound, 5th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.