ARDMS SPI Pulsed-Wave and CW Doppler 4

Question 1

What is the primary purpose of the fast Fourier transform (FFT) in spectral Doppler ultrasound?

Accepted Answer

To convert the raw Doppler audio signal into a frequency spectrum displayed over time

Answer

The FFT mathematically decomposes the complex Doppler signal into its individual frequency components, which are then displayed as a spectrum of velocities over time on the spectral waveform.

Question 2

A sonographer notes that the peak systolic velocity (PSV) appears falsely elevated when the sample volume is placed near a vessel bifurcation. What artifact is most likely responsible?

Accepted Answer

Intrinsic spectral broadening from a wide Doppler beam width at that depth

Answer

Intrinsic spectral broadening occurs because the Doppler beam has finite width; near a bifurcation the beam may intercept multiple vessels or disturbed flow regions, artificially broadening and elevating the displayed spectrum.

Question 3

In pulsed-wave Doppler, increasing the depth of the sample gate will require the system to:

Accepted Answer

Decrease PRF to allow sufficient time for echoes to return from the greater depth

Answer

Greater sample gate depth requires a longer round-trip travel time for the pulse echo, so PRF must be decreased to avoid range ambiguity.

Question 4

Which index is calculated as (PSV − EDV) / PSV and is used to describe the shape of an arterial Doppler waveform?

Accepted Answer

Pourcelot (Resistivity) Index

Answer

The Resistivity Index (RI), also called the Pourcelot Index, is (PSV − EDV) / PSV and reflects downstream vascular resistance; values range from 0 (no resistance) to 1 (absent diastolic flow).

Question 5

A sample volume placed just distal to a significant arterial stenosis would be expected to show which spectral Doppler finding?

Accepted Answer

A turbulent, broadened waveform with elevated peak velocity and possible aliasing

Answer

Immediately distal to a stenosis, the high-velocity jet and turbulent post-stenotic flow cause spectral broadening, elevated velocities, and often aliasing on the PW Doppler tracing.

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test

ARDMS SPI Pulsed-Wave and CW Doppler 4