ARDMS SPI Spectral Doppler Waveform Analysis 2 — Questions and Answers
Question 1: When the Doppler angle correction cursor is positioned at 90 degrees, the calculated velocity will be:
- Doubled compared to the true velocity
- Halved compared to the true velocity
- Equal to the true velocity
- Infinite or mathematically undefined (Correct answer)
Correct answer: Infinite or mathematically undefined
At 90 degrees, cos(90°) = 0, making the denominator of the Doppler equation zero, which produces a mathematically undefined (infinite) velocity value.
Question 2: Increasing the wall filter setting on a spectral Doppler display will:
- Remove high-frequency signals from the spectral display
- Remove low-frequency signals from the spectral display (Correct answer)
- Increase the Nyquist limit
- Decrease the pulse repetition frequency
Correct answer: Remove low-frequency signals from the spectral display
The wall filter (high-pass filter) eliminates low-frequency Doppler signals produced by slow-moving vessel walls and surrounding tissue, reducing clutter near the baseline.
Question 3: A 'tardus parvus' waveform observed distal to a stenosis is characterized by:
- Increased PSV with normal systolic acceleration time
- Decreased PSV with prolonged systolic acceleration time (Correct answer)
- Normal PSV with absent diastolic flow
- Increased RI with elevated diastolic velocities
Correct answer: Decreased PSV with prolonged systolic acceleration time
Tardus parvus (Latin: slow-small) describes the dampened, delayed post-stenotic waveform with reduced peak systolic velocity and a slow, rounded systolic upstroke.
Question 4: To correct aliasing on a spectral Doppler display, which of the following would NOT be an effective solution?
- Increasing the pulse repetition frequency (PRF)
- Shifting the spectral baseline
- Using a lower transmit frequency transducer
- Decreasing the sample volume gate size (Correct answer)
Correct answer: Decreasing the sample volume gate size
Decreasing sample volume size changes the amount of vessel sampled but does not affect the PRF or the Nyquist limit, making it ineffective for correcting aliasing.
Question 5: In a standard spectral Doppler display, the vertical (y-axis) represents:
- Time elapsed during the cardiac cycle
- Relative signal power or amplitude
- Doppler frequency shift (displayed as velocity after angle correction) (Correct answer)
- Depth of the sample volume gate
Correct answer: Doppler frequency shift (displayed as velocity after angle correction)
The y-axis in spectral Doppler displays the Doppler frequency shift, which is converted to velocity using angle correction, while the x-axis represents time.
Question 6: On a spectral Doppler display, flow moving AWAY from the transducer will appear:
- Above the baseline as a positive deflection
- Below the baseline as a negative deflection (Correct answer)
- Simultaneously above and below the baseline
- At the baseline without deflection
Correct answer: Below the baseline as a negative deflection
By convention, flow toward the transducer produces a positive frequency shift and appears above the baseline, while flow away from the transducer produces a negative shift and appears below the baseline.
Question 7: Which of the following best describes a low-resistance Doppler waveform?
- Triphasic flow pattern with reversal in early diastole
- Sharp systolic peak with absent end-diastolic flow
- Continuous forward flow throughout diastole with elevated end-diastolic velocity (Correct answer)
- Monophasic waveform with uniformly very low velocities
Correct answer: Continuous forward flow throughout diastole with elevated end-diastolic velocity
Low-resistance organs (kidney, brain, liver) require constant blood supply and maintain continuous forward flow throughout diastole, producing waveforms with elevated end-diastolic velocities.
ARDMS SPI Spectral Doppler Waveform Analysis 2
When the Doppler angle correction cursor is positioned at 90 degrees, the calculated velocity will be: