Color Doppler and Artifacts Flashcards

Which parameter, when increased, most effectively reduces color Doppler aliasing without changing the PRF?

Answer: Shift the baseline downward

Shifting the baseline extends the Nyquist limit in one direction, allowing higher velocities to be displayed without aliasing.

A color Doppler image shows a mosaic pattern within a vessel lumen. This most likely indicates:

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.

Which of the following best describes the color Doppler 'twinkling artifact'?

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.

When the color Doppler gate is positioned at 90° to flow direction, the resulting color display will show:

Answer: No color signal

At 90° insonation angle the Doppler frequency shift is zero, so no color signal is generated.

Color Doppler flash artifact is characterized by:

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.

Which color Doppler parameter directly controls the number of pulses used to estimate each color pixel?

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.

A color Doppler image of the carotid artery shows color signal extending beyond the vessel wall into surrounding soft tissue. This is called:

Answer: Color bleed (blooming)

Color bleed or blooming occurs when gain is set too high, causing color to spill beyond true vessel margins.