Chapter 6 Artifacts in Scanning H&A

Question 1

Movement of the zero Doppler-shift frequency or zero flow speed line up or down on a spectral display

Answer 1

Baseline shift

Question 2

Increase in echo amplitude from reflectors that lie behind a weakly attenuating structure

Answer 2

Enhancement

Question 3

Improper Doppler-shift information from a pulsed wave Doppler or color Doppler instrument when the true Doppler shift exceeds one half the pulse repetition frequency

Answer 3

Aliasing

Question 4

Series of closely spaced reverberation echoes

Answer 4

Comet tail

Question 5

Artifact produced when echoes are placed too close to the transducer because a second pulse was emitted before they were received

Answer 5

Range ambiguity

Question 6

Echo-free

Answer 6

Anechoic

Question 7

Leakage of strong signals in one direction channel of a Doppler receiver into the other channel; can produce the Doppler mirror-image artifact

Answer 7

Cross-talk

Question 8

Artifact resulting from a continuous stream of sound emanating from an anatomic site

Answer 8

Ring down

Question 9

Having relatively weak echoes

Answer 9

Hypoechoic

Question 10

Condition where a driven mechanical vibration is of a frequency similar to a natural vibration frequency of the structure

Answer 10

Resonance

Question 11

Several reflections produced by a pulse encountering a pair of reflectors; reverberation

Answer 11

Multiple reflection

Question 12

Artifactual gray-scale, color flow, or Doppler signal appearing on the opposite side (from the real structure or flow) of a strong reflector

Answer 12

Mirror image

Question 13

Doppler-shift frequency above which aliasing occurs; one half the pulse repetition frequency

Answer 13

Nyquist limit

Question 14

Multiple reflection

Answer 14

Reverberation

Question 15

Granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue

Answer 15

Speckle

Question 16

Thickness of the scanned tissue volume perpendicular to the scan plane; also called slice thickness

Answer 16

Section thickness

Question 17

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

Answer 17

Speed error

Question 18

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

Answer 18

Shadowing

Question 19

Propagation artifacts

Answer 19

Section thickness, speckle, reverberation, mirror image, refraction, grating lobes, speed error, range ambiguity.

Question 20

Attenuation artifacts

Answer 20

shadowing, and enhancement

Question 21

Additional beams emitted from an array transducer that are stronger than the side lobes of individual elements

Answer 21

Grading lobes