RVT Hemodynamics and Doppler Principles 3

Question 1

The Nyquist limit in pulsed wave Doppler determines the maximum detectable Doppler shift without aliasing, which equals:

Accepted Answer

Half the pulse repetition frequency (PRF/2)

Answer

Aliasing occurs when the Doppler shift exceeds the Nyquist limit, which is one-half of the pulse repetition frequency.

Question 2

Which factor does NOT affect the Doppler frequency shift?

Accepted Answer

Depth of the vessel

Answer

Depth affects PRF and time-gain compensation but is not a variable in the Doppler equation (fd = 2ft·v·cosθ / c).

Question 3

A peak systolic velocity ratio (stenotic/prestenotic) greater than 4.0 in the internal carotid artery typically indicates stenosis of:

Accepted Answer

70–99%

Answer

A velocity ratio greater than 4.0 is a validated criterion for ≥70% ICA stenosis, corresponding to hemodynamically significant disease.

Question 4

In continuous wave (CW) Doppler, the major advantage over pulsed wave Doppler is:

Accepted Answer

Ability to measure very high velocities without aliasing

Answer

CW Doppler has no PRF limitation and can accurately measure very high velocities, making it ideal for severe stenoses or cardiac jets.

Question 5

The spectral broadening seen in disturbed flow distal to a stenosis is caused by:

Accepted Answer

A wide range of velocities across the vessel lumen

Answer

Turbulent and disturbed flow creates multiple velocity vectors simultaneously, filling in the normally clear spectral window below the waveform.

(RVT) Registered Vascular Technologist Practice Test