ARDMS SPI Pulsed-Wave and CW Doppler 5 — Questions and Answers
Question 1: A 'tardus-parvus' waveform pattern on spectral Doppler is characterized by:
- A high-amplitude, sharp systolic peak with absent diastolic flow
- A dampened waveform with slow systolic rise (tardus) and reduced peak amplitude (parvus), seen distal to a significant proximal stenosis (Correct answer)
- Bidirectional flow above and below the baseline
- A triphasic high-resistance waveform with reverse flow
Correct answer: A dampened waveform with slow systolic rise (tardus) and reduced peak amplitude (parvus), seen distal to a significant proximal stenosis
Tardus-parvus describes the delayed systolic upstroke (tardus = slow) and reduced amplitude (parvus = small) seen in vessels distal to a significant upstream stenosis due to energy loss across the obstruction.
Question 2: In color Doppler imaging, the color assignment (red vs. blue) represents:
- Arterial versus venous flow
- Oxygenated versus deoxygenated blood
- Flow toward versus away from the transducer (Correct answer)
- High versus low velocity
Correct answer: Flow toward versus away from the transducer
Color Doppler encodes the mean Doppler frequency shift direction: by convention (BART — Blue Away Red Toward), red indicates flow toward the transducer and blue indicates flow away, regardless of vessel type.
Question 3: Which of the following is a recognized method to correct for aliasing in color Doppler without switching to power Doppler?
- Increasing the color gain
- Lowering the color scale (velocity range) further
- Increasing the color scale (velocity range / PRF) or shifting the baseline (Correct answer)
- Decreasing the transmit frequency
Correct answer: Increasing the color scale (velocity range / PRF) or shifting the baseline
Increasing the color scale raises the Nyquist limit for color Doppler, and shifting the color baseline allows more dynamic range in one direction to accommodate higher velocities without aliasing.
Question 4: What is the main advantage of power Doppler over conventional color flow Doppler?
- It shows the direction of flow
- It has greater sensitivity for detecting slow or low-volume flow and is less angle-dependent (Correct answer)
- It eliminates the need for the wall filter
- It measures velocity more accurately
Correct answer: It has greater sensitivity for detecting slow or low-volume flow and is less angle-dependent
Power Doppler displays the amplitude (power) of the Doppler signal rather than the mean frequency shift, making it more sensitive to slow flow and virtually angle-independent, though it sacrifices directional and velocity information.
Question 5: During a renal artery duplex examination, the acceleration time (AT) from a waveform sampled in the intrarenal arteries is measured at 0.12 seconds. This finding is:
- Normal; AT <0.07 s is the threshold for significant stenosis
- Abnormal; AT >0.07 s (some labs use >0.10 s) suggests hemodynamically significant proximal renal artery stenosis (Correct answer)
- Normal because AT should always exceed 0.10 s
- Irrelevant; only PSV is used for renal artery evaluation
Correct answer: Abnormal; AT >0.07 s (some labs use >0.10 s) suggests hemodynamically significant proximal renal artery stenosis
Acceleration time >0.07–0.10 seconds in intrarenal waveforms is associated with proximal renal artery stenosis; the prolonged upstroke reflects dampening of the waveform distal to the obstruction.
Question 6: Which of the following changes would increase the maximum velocity that can be measured without aliasing using PW Doppler?
- Increasing the transmit frequency
- Decreasing the sample gate depth (which allows a higher PRF) (Correct answer)
- Increasing the wall filter cutoff
- Increasing the Doppler angle to 60°
Correct answer: Decreasing the sample gate depth (which allows a higher PRF)
Shallower gate depth allows a higher PRF (less round-trip time needed), which raises the Nyquist limit and allows higher velocities to be measured without aliasing.
Question 7: In the Doppler equation, doubling the transmitted frequency while keeping all other variables constant will have what effect on the detected Doppler shift?
- The Doppler shift will be halved
- The Doppler shift will remain unchanged
- The Doppler shift will double (Correct answer)
- The Doppler shift will quadruple
Correct answer: The Doppler shift will double
Since Δf = 2f₀v cosθ / c, the Doppler shift is directly proportional to the transmitted frequency f₀; doubling f₀ doubles Δf when velocity, angle, and speed of sound remain constant.
ARDMS SPI Pulsed-Wave and CW Doppler 5
A 'tardus-parvus' waveform pattern on spectral Doppler is characterized by: