Krem Ch6 Flashcards
Aliasing
Improper Doppler shift information from a pulsed spectral Doppler or color Doppler instrument when the true Doppler shift exceeds one half the pulse repetition frequency.
Anechoic
Echo free.
Comet tail
A series of closely spaced reverberation echoes.
Cross-talk
Leakage of strong signals and One Direction channel of a Doppler receiver into the other channel; can produce the spectral Doppler mirror image artifact.
Enhancement
Increases in echo amplitude from reflectors that lie behind a weakly attenuating’s structure.
Hypoechoic
Having relatively weak echoes. Opposite of hyperechoic.
Mirror image
And artifactual grayscale, color flow, or Doppler signal appearing on the opposite side of a strong reflector.
Nyquist limit
The Doppler shift frequency above which aliasing occurs; one half of the pulse repetition frequency.
Range ambiguity
In artifact produced when echoes our place too close to the transducer because a second pulse was admitted before they were received from the first pulse
Reverberation
Multiple reflection.
Shadowing
Reduction in echo amplitude from reflectors that live behind a strongly reflecting or attenuating structure.
Slice thickness
Thickness of the scanned tissue volume perpendicular to the scanplane; also called section thickness.
Speckle
The granular appearance of the image and spectral display that caused by the interface of echoes from the distribution of scatters and tissue.
Speed error
Propagation speed that is different from the assumed value (1.54mm/Ms).
