Chapter 7 Flashcards
aliasing
improper Doppler-shift information from a pulsed spectral-Doppler or color-Doppler instrument when the true Doppler shift exceeds one-half the PRF.
anechoic
echo-free
comet tail
a series of closely spaced reverberation echoes.
cross-talk
leakage of strong signals in one direction channel of a Doppler receiver into the other channel
can produce the spectral-Doppler mirror image artifact.
enhancement
increase in echo amplitude from reflectors that lie behind a weakly attenuating structure.
hypoechoic
having relatively weak echoes.
opposite of hyperechoic.
mirror image
an artifactual gray-scale, color flow, or Doppler signal appearing on the opposite side (from the real structure or flow) of a strong reflector.
nyquist limit
the Doppler-shift freq1uency above which aliasing occurs.
one-half of the PRF.
range ambiguity
an artifact produced when echoes are placed too close to the transducer because a second pulse was emitted before they were received from he first pulse.
reverberation
multiple reflection.
shadowing
reduction in echo amplitude from reflectors that lie behind a strongly reflecting or attenuating structure.
slice thickness
thickness of the scanned tissue volume perpendicular to the scan plane.
also called section thickness.
speckle
the granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue.
speed error
propagation speeed that is different from the assumed value (1.54 mm/microsec).
