ARDMS SPI Spectral Doppler Waveform Analysis 1 — Questions and Answers
Question 1: Which formula correctly represents the Resistive Index (RI)?
- (PSV + EDV) / PSV
- (PSV - EDV) / PSV (Correct answer)
- (PSV - EDV) / EDV
- PSV / EDV
Correct answer: (PSV - EDV) / PSV
The RI (Pourcelot index) = (PSV - EDV) / PSV, producing a value between 0 and 1 that reflects downstream vascular resistance.
Question 2: Spectral broadening on a Doppler waveform indicates:
- Laminar flow with uniform velocities throughout the vessel
- A wide range of velocities simultaneously present within the sample volume (Correct answer)
- Increased downstream vascular resistance
- Optimal angle of insonation has been achieved
Correct answer: A wide range of velocities simultaneously present within the sample volume
Spectral broadening occurs when multiple velocity components are detected within the sample volume, filling in the clear spectral window beneath the waveform envelope.
Question 3: The spectral window in a Doppler display represents:
- The area of the vessel cross-section being sampled
- The frequency bandwidth of the transducer
- The clear area beneath the systolic peak where few slow-moving cells are present (Correct answer)
- The maximum detectable velocity before aliasing occurs
Correct answer: The clear area beneath the systolic peak where few slow-moving cells are present
The spectral window is the clear area beneath the waveform envelope, indicating relatively uniform laminar flow where most cells travel at similar velocities with few slow-moving cells near the vessel wall.
Question 4: Which Doppler insonation angle range provides the most accurate velocity measurement?
- 75–90 degrees
- 61–74 degrees
- 60 degrees or less (Correct answer)
- Angle does not affect velocity accuracy
Correct answer: 60 degrees or less
Angles of 60 degrees or less are recommended because the cosine function changes gradually in this range, minimizing the amplification of small angle errors in velocity calculations.
Question 5: A high-resistance spectral Doppler waveform is characterized by:
- High end-diastolic velocity with low peak systolic velocity
- Low or absent end-diastolic velocity with a sharp systolic peak (Correct answer)
- Continuous forward flow throughout the entire cardiac cycle
- Absent systolic peak with preserved diastolic flow
Correct answer: Low or absent end-diastolic velocity with a sharp systolic peak
High-resistance vessels (such as resting peripheral arteries) display a sharp systolic peak with little or no diastolic flow and may demonstrate brief flow reversal in early diastole.
Question 6: Aliasing on a spectral Doppler display is caused by:
- PRF set too high relative to the Doppler frequency shift
- PRF set too low relative to the Doppler frequency shift (Correct answer)
- Incorrect angle of insonation greater than 60 degrees
- Sample volume placed too far from the vessel wall
Correct answer: PRF set too low relative to the Doppler frequency shift
Aliasing occurs when the Doppler frequency shift exceeds half the PRF (the Nyquist limit), causing high-velocity signals to wrap around and appear on the opposite side of the baseline.
Question 7: The Pulsatility Index (PI) is calculated as:
- (PSV - EDV) / PSV
- PSV / EDV
- (PSV - EDV) / TAMV (Correct answer)
- (PSV + EDV) / 2
Correct answer: (PSV - EDV) / TAMV
PI = (PSV - EDV) / TAMV (time-averaged mean velocity); unlike RI, PI can exceed 1.0 and can be calculated even when end-diastolic flow is zero or reversed.
ARDMS SPI Spectral Doppler Waveform Analysis 1
Which formula correctly represents the Resistive Index (RI)?