ARDMS SPI Color Doppler and Artifacts 5 — Questions and Answers
Question 1: Which statement about directional power Doppler (DPD) is correct?
- DPD has lower sensitivity than conventional color Doppler
- DPD displays both flow direction and amplitude but with less flash artifact than power Doppler (Correct answer)
- DPD uses a higher PRF than conventional color Doppler
- DPD eliminates aliasing completely
Correct answer: DPD displays both flow direction and amplitude but with less flash artifact than power Doppler
Directional power Doppler combines the sensitivity of power Doppler with directional encoding while offering some reduction in flash artifact compared to standard power Doppler.
Question 2: On color Doppler, a vessel showing reversed color assignment relative to the adjacent artery in the same image most likely indicates:
- Flash artifact
- Venous flow direction opposite to arterial flow (Correct answer)
- Nyquist limit exceeded
- Wall filter set too low
Correct answer: Venous flow direction opposite to arterial flow
Veins normally carry blood in the opposite direction to adjacent arteries, producing the opposite color assignment by convention.
Question 3: The acoustic streaming artifact in color Doppler is seen as:
- Color signal within a fluid-filled cyst caused by acoustic radiation force (Correct answer)
- Color aliasing in a deep vessel
- Color bleed from a hyperechoic mass
- Twinkling behind a stone
Correct answer: Color signal within a fluid-filled cyst caused by acoustic radiation force
Acoustic streaming occurs when ultrasound radiation force displaces fluid within a cyst, producing color Doppler signal in an otherwise avascular structure.
Question 4: When evaluating a small vessel for low-velocity flow, which transducer choice optimizes color Doppler sensitivity?
- Low-frequency curved array with high PRF
- High-frequency linear array with low PRF (Correct answer)
- Phased array with wide color box
- Mechanical sector probe with maximum depth
Correct answer: High-frequency linear array with low PRF
A high-frequency linear array provides better spatial resolution for small vessels, and low PRF lowers the Nyquist limit to detect slow flow.
Question 5: Color Doppler 'color bruit' (perivascular color artifact) around an AV fistula is caused by:
- High-velocity turbulent flow causing tissue vibration that is detected as Doppler shifts (Correct answer)
- Color bleed from high gain settings
- Mirror image of the vessel
- Flash artifact from patient breathing
Correct answer: High-velocity turbulent flow causing tissue vibration that is detected as Doppler shifts
Tissue vibration from high-velocity turbulent flow in an AV fistula generates low-frequency Doppler shifts in surrounding soft tissue, producing a color bruit.
Question 6: Increasing the persistence (temporal averaging) setting in color Doppler will:
- Improve detection of pulsatile rapid flow changes
- Smooth the color display but reduce temporal resolution (Correct answer)
- Increase the PRF automatically
- Eliminate aliasing artifact
Correct answer: Smooth the color display but reduce temporal resolution
Higher persistence averages more frames, producing a smoother color image but blurring rapid phasic changes in flow.
Question 7: Which of the following correctly describes the relationship between color Doppler frame rate and color box size?
- Wider color box increases frame rate because fewer pulses are needed
- Narrower color box increases frame rate by reducing the number of scan lines required (Correct answer)
- Color box size has no effect on frame rate
- Deeper color box increases frame rate by lowering PRF
Correct answer: Narrower color box increases frame rate by reducing the number of scan lines required
A narrower color box requires fewer scan lines per frame, allowing the system to complete each frame more quickly and increasing frame rate.
ARDMS SPI Color Doppler and Artifacts 5
Which statement about directional power Doppler (DPD) is correct?