Regarding colour flow imaging (CFI) and power Doppler imaging: a. Ima

1.	Regarding colour flow imaging (CFI) and power Doppler imaging: a. Image acquisition in CFI is based on the continuous-wave Doppler b. CFI is not susceptible to aliasing c. On modern ultrasound equipment, the frame rate achieved in colour flow mode is the same as the frame rate in the corresponding pure B-mode imaging d. In power Doppler imaging, the sensitivity to motion is not dependent on the Doppler angle e. CFI is more susceptible to flash artefacts than power Doppler imaging
Answer» a. False. CFI uses pulsed-wave Doppler acquisition. Multiple pulses are sent over multiple lines and Doppler shifts are obtained from multiple gates along these lines. Information is presented on a 2D map of flow usually superimposed on a B-mode picture, with colour-coded direction of flow. To speed up data acquisition and processing, phase-shift auto correlation or time domain correlation is used together with faster analysis algorithms. b. False. The same Nyquist criterion applies as with spectral pulsed-wave Doppler imaging. c. False. The frame rate in CFI is always lower than in pure B-mode imaging, as multiple pulses (typically 2–20) are sent for each scan line. The Doppler pulses will also need to be interleaved with B-mode imaging pulses, further decreasing the frame rate. d. True. Power Doppler (energy Doppler) imaging ignores information about the direction and velocity of flow and displays information dependent only on the flow amplitude. This does not change significantly with the angle of insonation. e. False. As the name implies, flash artefacts are bursts of signal resulting from the motion of tissue. As power Doppler imaging is more sensitive to motion, flash artefacts are more likely to occur.

Regarding colour flow imaging (CFI) and power Doppler imaging: a. Image acquisition in CFI is based on the continuous-wave Doppler b. CFI is not susceptible to aliasing c. On modern ultrasound equipment, the frame rate achieved in colour flow mode is the same as the frame rate in the corresponding pure B-mode imaging d. In power Doppler imaging, the sensitivity to motion is not dependent on the Doppler angle e. CFI is more susceptible to flash artefacts than power Doppler imaging

Answer»

a. False. CFI uses pulsed-wave Doppler acquisition. Multiple pulses are sent over multiple lines and Doppler shifts are obtained from multiple gates along these lines. Information is presented on a 2D map of flow usually superimposed on a B-mode picture, with colour-coded direction of flow. To speed up data acquisition and processing, phase-shift auto correlation or time domain correlation is used together with faster analysis algorithms.

b. False. The same Nyquist criterion applies as with spectral pulsed-wave Doppler imaging.

c. False. The frame rate in CFI is always lower than in pure B-mode imaging, as multiple pulses (typically 2–20) are sent for each scan line. The Doppler pulses will also need to be interleaved with B-mode imaging pulses, further decreasing the frame rate.

d. True. Power Doppler (energy Doppler) imaging ignores information about the direction and velocity of flow and displays information dependent only on the flow amplitude. This does not change significantly with the angle of insonation.

e. False. As the name implies, flash artefacts are bursts of signal resulting from the motion of tissue. As power Doppler imaging is more sensitive to motion, flash artefacts are more likely to occur.

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