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Physics > Artifacts > Flashcards

Artifacts Flashcards

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1
Q

All artifacts are bad and should be eliminated.

T/F

A

False

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2
Q

What assumptions are made with ultrasound?

A

Sound travels in straight line
Reflections are produced by structures along main axis of beam
Intensity of echo corresponds to reflectors scattering strength
Imaging plane is thin
Sound travels to/from directly
Always travels at 1.54 mm/us

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3
Q

How can axial resolution cause artifact?

A

When two structures along axis of beam are mistaken as one

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4
Q

Artifact because of poor lateral resolution contributes to:

A

Incorrect representation of size and shape and to missing interfaces

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5
Q

What is acoustic speckle?

A

Granular appearance of images and spectral displays

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6
Q

What causes acoustic speckle?

A

Interference of echoes from distribution of scatterers in tissue

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7
Q

Where does acoustic speckle most often occur?

A

Near face of transducer

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8
Q

What interferes with the ability of the system to detect low-contrast objects?

A

Acoustic speckle

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9
Q

Elevational resolution artifacts can cause misdiagnosis when:

A

Echo fill-in occurs in cystic structure

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10
Q

Reverberation appears as:

A

More interfaces than actually exist

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11
Q

What helps counteract reverberation?

A

Harmonics

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12
Q

A type of reverb caused by metal objects:

A

Comet tail

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13
Q

Reverb produced by small gas bubbles

A

Ring down

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14
Q

Comet tail appears as multiple small bands that taper in gray scale.
T/F

A

False

In color

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15
Q

Where will the duplicate mirror image appear?

A

ALWAYS deeper than true structure

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16
Q

Multi path artifacts result in:

A

Improper brightness

Makes structure look farther away due to increase travel time of beam

17
Q

Refraction can produce what kind of artifacts?

A

Edge shadowing with round structures

Ghost image artifact

18
Q

What is a ghost image artifact?

A

A duplication of structures that appear side by side caused by refraction of the beam off the rectus abdominus muscle
*in transverse

19
Q

Side lobes correspond with:

A

Single crystal transducers

20
Q

Grating lobes correspond with:

A

Array transducers

21
Q

Side lobes or grating lobes are caused by:

A

Acoustic energy emitted in a direction different than from main axis of sound beam

22
Q

Side lobes / grating lobes make the reflection appear:

A

At correct depth but lateral to true anatomy

23
Q

Subdicing and apodization help counteract side lobes.

T/F

A

False, grating lobes

24
Q

If propagation speed in mass is faster than 1.54 mm/us then the mass will appear:

A

Too close to the transducer

25
Q

If the propagation speed in a mass is slower than 1.54 mm/us the reflector will appear:

A

Too far from the transducer

26
Q

Shadowing occurs when the sound beam intersects with a:

A

Highly attenuating structure

Ex: calcium/bone

27
Q

Name two artifacts that are helpful with diagnosis.

A

Shadowing and enhancement

28
Q

Near field artifact is caused by:

A

Reverberation

29
Q

Common manifestation of color Doppler aliasing?

A

Wrap around of display, appears as reversal of flow

30
Q

Ghosting with color Doppler shows:

A

True vessel closest to transducer with artifactual vessel below it

31
Q

Cross talk occurs when:

A

Doppler gain is set too high or angle close to 90 degrees

32
Q

What does crosstalk look like?

A

Shows waveform above and below baseline

33
Q

Blossoming is another term for:

A

Color bleed

34
Q

How can you eliminate color bleed?

A

Decreasing color gain

35
Q

Color noise/clutter can be eliminated by:

A

Adjusting the wall filter

36
Q

Ghosting may refer to:

A

Mirror imaging or when color is improperly assigned to stationary structures

Physics (4 decks)

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