Question 1

Shadowing and enhancement are descriptions of ________ artifacts.

Accepted Answer

Attenuation artifacts include enhancement,shadowing,edge shadowing,and focal enhancement (focal banding).

Question 2

There must be ________ samples per cycle of Doppler shift to correctly obtain an image.

Accepted Answer

At least two samples per cycle of the desired Doppler shift must be made for the image to be correctly obtained.

Question 3

Which of the following is not a form of reverberation artifact?

Accepted Answer

Reverberation artifact demonstrates multiple reflections as seen with ring-down,mirror-image,and comet-tail artifacts.Speckle is a result of the interference effects of the scattered sound.

Question 4

Which artifact displaces structures axially?

Accepted Answer

Propagation speed displaces structures axially.Multiple reflections are displayed beneath the real reflector with reverberation artifacts.

Question 5

Axial resolution is determined by ________ and lateral resolution is determined by ________.

Accepted Answer

Axial resolution is determined by the spatial pulse length,and lateral resolution is determined by the pulse width.

Question 6

Mirror image is commonly seen around which structure?

Accepted Answer

Mirror image artifacts are commonly visualized around the diaphragm and pleura.

Question 7

Increased intensity of echoes in the focal region of the beam is called _______.

Accepted Answer

Brightening of echoes in the focal region is called focal banding or focal enhancement.

Question 8

How is detail resolution artifactual?

Accepted Answer

Limited detail resolution can introduce artifacts because a failure to resolve means a loss of detail and two adjacent structures are seen are one.

Question 9

Mirror-image artifact is a form of ________.

Accepted Answer

Mirror-image artifact is a form of reverberation.

Question 10

Speckle artifact is most likely caused by ________.

Accepted Answer

Speckle artifact is most likely caused by the interference effects of the scattered sound from the distribution of all the scatterers within the tissue.

Question 11

Which type of artifact is most likely to produce a doubling of a single image?

Accepted Answer

Refraction is most likely to produce doubling of a single image,especially when imaging over the abdominis rectus muscles.

Question 12

Echo reflections that produce bright and dark spots in the gray-scale image are called ________.

Accepted Answer

Speckle produces the familiar pattern of bright and dark spots in the gray-scale image.

Question 13

The comet-tail artifact is a case of ________.

Accepted Answer

The comet-tail artifact is a case of reverberation where two closely spaced surfaces generate a series of closely spaced discrete echoes.

Question 14

Multiple reflections between two structures describes

Accepted Answer

Reverberations (multiple reflections) can occur between two strong reflections.Mirror image is a form of reverberation but demonstrates structures that exist on one side of a strong reflector as being present on the other side as well.

Question 15

Weakening of echoes distal to a strongly attenuating structure describes ________.

Accepted Answer

Shadowing is the reduction in echo amplitude from reflectors that lie behind a strongly reflecting or attenuating structure.

Question 16

Which of the following is an effect of refraction?

Accepted Answer

Refraction of the sound beam at the edges of structures displays structures laterally.No echoes return where this occurs,resulting in edge shadowing.

Question 17

Section thickness artifact is also called ________.

Accepted Answer

Section thickness artifact is also called slice thickness or partial-volume artifact.

Question 18

It may be possible to resolve slice thickness artifact by ________.

Accepted Answer

It may be possible to resolve this artifact by using tissue harmonics imaging,because the sound beam in this mode is narrower than in regular gray-scale mode.

Question 19

Which of the following would most likely eliminate spectral aliasing?

Accepted Answer

Increasing the Doppler angle decreases the Doppler shift for a given flow,which is most likely to eliminate spectral aliasing.

Question 20

Enhancement of an echo results from a structure having ________ than surrounding structures.

Accepted Answer

Enhancement is the strengthening of echoes distal to a weakly attenuating structure.

Quiz 6: Artifacts