ARDMS SPI Color Doppler and Artifacts 2 — Questions and Answers
Question 1: Which parameter, when increased, most effectively reduces color Doppler aliasing without changing the PRF?
- Increase color gain
- Shift the baseline downward (Correct answer)
- Decrease wall filter
- Increase ensemble length
Correct answer: Shift the baseline downward
Shifting the baseline extends the Nyquist limit in one direction, allowing higher velocities to be displayed without aliasing.
Question 2: A color Doppler image shows a mosaic pattern within a vessel lumen. This most likely indicates:
- Laminar flow at high velocity
- Turbulent or disturbed flow with aliasing (Correct answer)
- Color bleed from adjacent tissue
- Incorrect wall filter setting
Correct answer: Turbulent or disturbed flow with aliasing
A mosaic pattern of mixed colors represents turbulent flow combined with aliasing, commonly seen distal to a stenosis.
Question 3: Which of the following best describes the color Doppler 'twinkling artifact'?
- Rapidly alternating red and blue pixels behind a strongly reflective surface (Correct answer)
- Color signal appearing in an avascular structure
- Bidirectional flow displayed at a valve
- Acoustic shadowing with color dropout
Correct answer: Rapidly alternating red and blue pixels behind a strongly reflective surface
The twinkling artifact produces rapidly flickering red and blue pixels posterior to calcifications or stones due to phase jitter.
Question 4: When the color Doppler gate is positioned at 90° to flow direction, the resulting color display will show:
- Maximum color saturation
- Aliasing
- No color signal (Correct answer)
- Reversed color assignment
Correct answer: No color signal
At 90° insonation angle the Doppler frequency shift is zero, so no color signal is generated.
Question 5: Color Doppler flash artifact is characterized by:
- Persistent color signal in a cyst
- Transient color fill of entire image from tissue motion (Correct answer)
- Color dropout in a high-velocity jet
- Reverberant color stripes
Correct answer: Transient color fill of entire image from tissue motion
Flash artifact occurs when patient or probe motion generates low-frequency Doppler shifts that briefly fill the color box with color.
Question 6: Which color Doppler parameter directly controls the number of pulses used to estimate each color pixel?
- Color gain
- Wall filter
- Ensemble length (packet size) (Correct answer)
- Color priority
Correct answer: Ensemble length (packet size)
Ensemble length (packet size) is the number of pulses per scan line used for color velocity estimation; more pulses improve sensitivity but reduce frame rate.
Question 7: A color Doppler image of the carotid artery shows color signal extending beyond the vessel wall into surrounding soft tissue. This is called:
- Color bleed (blooming) (Correct answer)
- Twinkling artifact
- Mirror image artifact
- Color aliasing
Correct answer: Color bleed (blooming)
Color bleed or blooming occurs when gain is set too high, causing color to spill beyond true vessel margins.
ARDMS SPI Color Doppler and Artifacts 2
Which parameter, when increased, most effectively reduces color Doppler aliasing without changing the PRF?