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DSM PHY > Physics 2 Test Ch 21 > Flashcards

Physics 2 Test Ch 21 Flashcards

1
Q

Causes of artifacts

A 
Violation of assumptions
Equipment malfunction/poor design
Physics of ultrasound
Operator error
pg. 355
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2
Q

Types of artifacts

A 
Not real
Not seen on image
Incorrect shape or size
Incorrect position
Incorrect brightness
pg. 355
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3
Q

Characteristics of artifacts

A 
Hyperechoic 
Hypoechoic 
Anechoic 
Isoechoic 
Homogenous
Heterogenous
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4
Q

Assumptions of artifacts

A
  1. Sound travels in a straight line
  2. Sound travels directly to a reflector and back
  3. Sound travels in soft tissue at exactly 1540 m/s
  4. Reflections arise only from structures positioned in the beam’s main axis
  5. The imaging plane is very thin
  6. The strength of a reflection is related to the characteristics of the tissue creating the reflection
    pg. 356
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5
Q

Characteristics of reverberation

A 
Appear in multiples
Appear equally spaced 
Located parallel to sound beam's main axis
Located at ever-increasing depths
pg. 357
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6
Q

What artifact appears as multiple, equally spaced echoes caused by the bouncing of the sound wave between 2 strong reflectors positioned parallel to the ultrasound beam?

A

Reverberation

pg. 357

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7
Q

What artifact appears as a solid hyperechoic line directed downward?

A

Comet tail
aka Ring down artifact
pg. 358

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8
Q

What are the characteristics of comet tail?

A

Single long hyperechoic echo
Located parallel to sound beam’s main axis
pg. 358

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9
Q

What artifact appears as a hypoechoic or anechoic region extending downward from a highly attenuating structure?

A

Shadow

pg. 359

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10
Q

What are the characteristics of shadowing?

A

Hypo- or anechoic background
Result of too much attenuation
Located beneath the structure with abnormally high attenuation
Prevents visualization of true anatomy on the scan
pg. 359

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11
Q

What artifact is a special form of shadowing that appears as a hypoechoic region extending down from the edge of a curved reflector?

A

Edge shadow

pg. 360

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12
Q

What artifact appears as a hyperechoic region beneath tissues with abnormally low attenuation?

A

Enhancement

pg. 361

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13
Q

What are the characteristics of enhancement?

A

Hyperechoic
Result of too little attenuation
Located beneath a structure with abnormally low attenuation
pg. 361

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14
Q

What artifact is a special form of enhancement in which a side-to-side region of an image appears brighter than tissues at other depths?

A

Focal enhancement
aka Focal banding
pg. 362

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15
Q

What artifact is created when sound reflects off a strong reflector and is redirected toward a second structure?

A

Mirror image

pg. 363

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16
Q

What are the characteristics of mirror image?

A

A second copy of a true reflector
Located deeper than true reflector
The mirror lies on a straight line between the artifact and transducer
True reflector and artifact are equal distances from mirror
pg. 363

17
Q

What is crosstalk?

A

Mirror image on a spectral Doppler display

pg. 363

18
Q

What artifact is created when a sound wave propagates through a medium at a speed other than soft tissue?

A

Speed error

pg. 364

19
Q

What are the characteristics of speed error?

A

Correct number of reflections
Improper depth
Appears as a step-off
pg. 365

20
Q

What artifact appears when sound energy is transmitted in a direction other than along the beam’s main axis?

A

Lobes

pg. 366

21
Q

What resolution is degraded with lobe artifact?

A

Lateral resolution

pg. 366

22
Q

What are the characteristics of lobe artifact?

A

Second copy of the true reflector
The artifact and true reflector are located side-by-side at the same depth
pg. 366

23
Q

Which transducer creates side lobes?

A

Mechanical probe

pg. 367

24
Q

What transducer creates grating lobes?

A

Array transducers

pg. 367

25
Q

What artifact is created when a sound pulse changes direction during transmission?

A

Refraction

pg. 368

26
Q

What are the characteristics of refraction?

A

Second copy of the reflector
The copy is side-by-side and the same depth of the true reflector
pg. 368

DSM PHY (14 decks)

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