ARDMS SPI Color Doppler and Artifacts 3 — Questions and Answers
Question 1: In power Doppler imaging compared to conventional color Doppler, which of the following is TRUE?
- Power Doppler displays directional flow information
- Power Doppler is more sensitive to low-velocity flow (Correct answer)
- Power Doppler has less flash artifact
- Power Doppler uses a lower PRF
Correct answer: Power Doppler is more sensitive to low-velocity flow
Power Doppler maps the amplitude (power) of the Doppler signal, making it more sensitive to slow flow but sacrificing directional information.
Question 2: Which artifact causes a color Doppler signal to appear on the opposite side of a strong reflector at the same depth?
- Acoustic enhancement
- Mirror image artifact (Correct answer)
- Aliasing
- Range ambiguity
Correct answer: Mirror image artifact
Mirror image artifact duplicates the Doppler signal symmetrically on the opposite side of a specular reflector such as the pleura.
Question 3: The wall filter in color Doppler primarily removes signals from:
- High-velocity arterial flow
- Aliased signals
- Low-frequency shifts caused by slow-moving tissue (Correct answer)
- Signals beyond the Nyquist limit
Correct answer: Low-frequency shifts caused by slow-moving tissue
The wall filter (high-pass filter) eliminates low-frequency Doppler shifts produced by vessel walls and surrounding tissue motion.
Question 4: Range ambiguity artifact in color Doppler occurs when:
- The beam steers at too shallow an angle
- A second pulse is transmitted before echoes from the first pulse are received (Correct answer)
- Gain is set too high
- The ensemble length is too short
Correct answer: A second pulse is transmitted before echoes from the first pulse are received
When PRF is too high for the imaging depth, returning echoes from deep structures arrive after the next pulse is sent, causing misregistration of color signals.
Question 5: Color Doppler sensitivity to slow flow is best improved by which combination of settings?
- High PRF, low ensemble length, high wall filter
- Low PRF, high ensemble length, low wall filter (Correct answer)
- High PRF, high gain, high wall filter
- Low gain, low PRF, high wall filter
Correct answer: Low PRF, high ensemble length, low wall filter
Low PRF extends the velocity range downward, high ensemble length improves signal averaging, and low wall filter preserves slow-flow frequencies.
Question 6: On a color Doppler image, a vessel appears with both red and blue colors side by side in a straight segment. The most likely explanation is:
- Turbulent flow
- Correct color map assignment
- The vessel curves so one limb moves toward and one away from the transducer (Correct answer)
- Aliasing at peak systole
Correct answer: The vessel curves so one limb moves toward and one away from the transducer
When a vessel curves, different portions move toward and away from the transducer, producing opposite color assignments even in laminar flow.
Question 7: Which of the following increases the risk of color Doppler aliasing?
- Decreasing imaging depth
- Increasing the color box size to include deeper structures (Correct answer)
- Lowering the color gain
- Narrowing the color box width
Correct answer: Increasing the color box size to include deeper structures
Greater imaging depth requires a lower PRF, which lowers the Nyquist limit and increases aliasing for a given flow velocity.
ARDMS SPI Color Doppler and Artifacts 3
In power Doppler imaging compared to conventional color Doppler, which of the following is TRUE?