Krem Ch6

Question 1

Aliasing

Answer 1

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.

Question 2

Anechoic

Answer 2

Echo free.

Question 3

Comet tail

Answer 3

A series of closely spaced reverberation echoes.

Question 4

Cross-talk

Answer 4

Leakage of strong signals and One Direction channel of a Doppler receiver into the other channel; can produce the spectral Doppler mirror image artifact.

Question 5

Enhancement

Answer 5

Increases in echo amplitude from reflectors that lie behind a weakly attenuating’s structure.

Question 6

Hypoechoic

Answer 6

Having relatively weak echoes. Opposite of hyperechoic.

Question 7

Mirror image

Answer 7

And artifactual grayscale, color flow, or Doppler signal appearing on the opposite side of a strong reflector.

Question 8

Nyquist limit

Answer 8

The Doppler shift frequency above which aliasing occurs; one half of the pulse repetition frequency.

Question 9

Range ambiguity

Answer 9

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

Question 10

Reverberation

Answer 10

Multiple reflection.

Question 11

Shadowing

Answer 11

Reduction in echo amplitude from reflectors that live behind a strongly reflecting or attenuating structure.

Question 12

Slice thickness

Answer 12

Thickness of the scanned tissue volume perpendicular to the scanplane; also called section thickness.

Question 13

Speckle

Answer 13

The granular appearance of the image and spectral display that caused by the interface of echoes from the distribution of scatters and tissue.

Question 14

Speed error

Answer 14

Propagation speed that is different from the assumed value (1.54mm/Ms).