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SPI > Artifacts > Flashcards

Artifacts Flashcards

1
Q

Multiple equally spaced echoes caused by the bouncing of the sound wave between two strong reflectors positioned parallel to us beam

A

Reverberation

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2
Q

Reverberation resembles a

A

Ladder

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3
Q

Solid hyperechoic line directed downward. Created when closely spaced reverberations merge.

A

Comet tail

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4
Q

Appears when a sound wave bounces back and forth between two verily closely spaced objects

A

Comet tail

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5
Q

Hypoechoic or anechoic region appears when attenuation is higher

A

Shadow

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6
Q

Shadowing is unrelated to ___ in a medium

A

Speed of sound

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7
Q

Hypoechoic region extending down from the edge of a curved reflector caused by a decrease in intensity

A

Edge shadowing / shadowing by refraction

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8
Q

Hyperechoic beneath tissues with low attenuation

A

Enhancement

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9
Q

Special form of enhancement, in which a side to side region of an image appears brighter than tissues, that other depths

A

Focal enhancement / focal banding

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10
Q

Focal enhancement results from ____ at the focus

A

Increased intensity

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11
Q

This artifact is located deeper than the real structure. Sound reflects off a strong reflector and is redirected toward a second structure.

A

Mirror image

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12
Q

6 assumptions of imaging systems

A

1) sound travels in a straight line
2) sound travels directly to reflector
3) sounds travels at 1540 m/s
4) imaging plane is very thin
5) reflections arise only from structures positioned in the beams main axis
6)the strength of the reflection is related to characteristics of the tissue creating the reflection

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13
Q

Useful artifacts

A

shadowing and enhancement

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14
Q

Mirror image artifact that appears on a spectral doppler display

A

crosstalk

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15
Q

Appears as a step off and created when a sound wave propogates through a medium at a speed other than 1.54 mm/us

A

Speed error

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16
Q

There a correct number of reflectors but has an improper debth

A

speed error

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17
Q

When sound energy is transmitted in a direction other than along the beams main axis

A

lobe artifact

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18
Q

lobe artifact degrades

A

temporal resolution

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19
Q

Lobes created by a single crystal transducer such as a mechanical probe

A

side lobes

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20
Q

lobes created by array transducers are

A

grating lobes

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21
Q

Reducing lobe artifacts in 2 ways

A

subdicing and apodization

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22
Q

dividing each pzt element into small pieces

A

subdicing

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23
Q

Process of differential excitation.
exiting the subdiced elements with a different voltage

A

apodization

24
Q

Created when a sound pulse changes direction during transmission and occurs when a sound wave strikes a boundary obliquely

A

Refraction

25
Q

Refraction degrades

A

lateral resolution

26
Q

side by side or same depth of the true reflector

A

Refraction

27
Q

Slice thickness is also called

A

section thickness artifact / partial volume artifact

28
Q

Related to the dimension of the beam that is perpendicular to the imaging plane

A

Slice thickness artifact

29
Q

Determined by the thickness of the imaging plane

A

Elevation resolution

30
Q

Anatomic reflectors absent on an image

A

shadowing, lateral resolution, axial resolution

31
Q

Artifact positioned deeper than true anatomy

A

comet tail, ring down, reverberation, mirror image

32
Q

Artifacts displayed to the side of true anatomy

A

refraction, side lobe, grating lobe

33
Q

Anatomic structures appear at incorrect depth

A

Speed errors, range ambiguity artifact

34
Q

Which artifact is unrelated to the dimensions of an us pulse

A

refraction

35
Q

It is common to visualize artifacts when the dimension of the sound beam is ____ than the reflectors dimension

A

Larger

36
Q

Which artifact produced an image with an incorrect number or reflectors

A

Side lobes

37
Q

What determines spatial resolution of a digital display

A

pixel density

38
Q

What determines spatial resolution of a display

A

Number of lines on the display

39
Q

Lateral resolution can be approved by

A

focusing because it narrows the beam width

40
Q
A
41
Q

Low line density degrades

A

spatial resolution

42
Q

What alters low velocity flows while leaving high velocity flow unchanged

A

Wall filter

43
Q

Alter low velocity flows while leaving high velocity flow unchanged

A

Wall filter

44
Q

What determines the spatial resolution in a digital display

A

Pixel density

45
Q

This artifact produces an image with an incorrect number of reflectors

A

Side lobes

46
Q

What happens to the position of all echoes produced from reflectors shallower than the mass

A

They are placed at the correct depth

47
Q

What happens to the position of echoes from reflectors deeper than the mass

A

They are placed in too deep a location on the image

48
Q

What type of artifact causes a reflection to be placed at an incorrect depth

A

Range ambiguity

49
Q

Acoustic energy radiating in a direction other than the beams main axis causes

A

Side lobe artifact

50
Q

Grating loves are most common with what transducers

A

Linear array

51
Q

Technique to eliminate grating lobe artifact

A

Subdicing

52
Q

How does slice thickness express itself

A

Fill in cystic structures

53
Q

With depth resolution there are ___ reflectors on the image

A

Too few

54
Q

What is a comet tail artifacts fundamental mechanism of formation

A

Reflection

55
Q

What haze the higher value / axial or lateral

A

Lateral

56
Q

When do artifacts appear

A

When the dimensions of a sound beam area is larger than the dimensions of the reflectors in the body

SPI (16 decks)

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