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DMST 315 OBGYN 3 > Module 16 Artifacts > Flashcards

Module 16 Artifacts Flashcards

1
Q

What are four primary assumptions of artifacts?

A
  1. The beam travels in a straight line
  2. The retuning pulse is received before the next pulse is sent
  3. The round trip time of the pulse is proportional to the distance travelled
  4. Objects viewed are located in the central portion of the sound beam
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2
Q

Are the four primary assumptions of artifacts always true?

A

No

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3
Q

What are artifacts that clarify? 4

A
  1. Attenuation
  2. Enhancement
  3. Shadow
  4. Comet tail
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4
Q

What are artifacts that confuse? 5

A
  1. Refraction
  2. Reflection
  3. Reverberation
  4. Side lobes
  5. Ring down
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5
Q

What can be noted in terms of reflections and sound travel?

A

Sound does not always travel in a straight line

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6
Q

In terms of reflection what affects the pathway of sound?

A

It depends on the change in velocity of sound travelling from one medium to another

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7
Q

What happens with sound Beams with reflections?

A

The sound beam bounces off the interface without entering the second medium which displaces information

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8
Q

What kind of reflector does reflection usually occur with?

A

Specular reflector

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9
Q

What happens in terms of reflection in this image?

A

Incorrect information placed at the edge of the fetal head

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10
Q

What does refraction do to the acoustic beam as it travels?

A

Changes the direction

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11
Q

Where does the information in the acoustic beam go in terms of refraction?

A

Information is placed in a different location

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12
Q

What are examples of refraction artifacts?

A

Edge shadowing and duplication

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13
Q

When does curved edge refraction shadows happen?

A

When the beam hits a curve Specular reflector (edge of cysts and bones or canal of cervix)

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14
Q

How many types of curved edge refraction shadows are there? And what are they?

A

2 types

  1. 1st type: Low velocity medium to high velocity medium see a wide shadow
  2. 2nd type: From high velocity medium to low velocity medium see a narrow shadow
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15
Q

In terms of this image what is happening with this image? And what is the process of it happening?

A

Curved edge refraction shadow

  1. Beam hits a curved Specular reflector
  2. Low velocity maternal soft (tissue) to high velocity (bone)
  3. Thick shadow is produced
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16
Q

What artifact is this an example of?

A

Refraction

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17
Q

What is this an example of?

A

Curved edge refraction from a fibroid

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18
Q

What is happening in this image?

A

There is a shadow on the left of the cranium. We need to adjust the angle to see the full image of the skull

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19
Q

What happens with a critical angle?

A

The sound beam is completely reflected when the angle of transmission and angle of incidence equals 90 degrees

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20
Q

What does a critical angle cause?

A

Produces a wide shadow deep to tissue that should not shadow

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21
Q

How does a split image artifact happen?

A

When the beam travels through fat, then muscle, it is no longer in a straight line. The machine does not compensate for this

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22
Q

What causes split image artifacts?

A

Refraction

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23
Q

What might we see in terms of split image artifacts?

A

We may see partial or complete duplication of structures

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24
Q

What are examples in the body we may see split image artifacts?

A
  1. Linea alba
  2. Pseudo twin gestational sacs
25
Q

What is this an example of?

A

Split image artifacts

26
Q

What is a heterotropic pregnancy?

A

Multiple pregnancies

27
Q

What is reverberation?

A

Multiple reflections of sound between a structure and the transducer face

28
Q

What kind of structures does reverberation occur in?

A

In structures with a high degree of mismatch

29
Q

What are examples of structures reverberation occur with?

A

Bone and soft tissue

30
Q

What can reverberation be described as looking like?

A
  1. Equidistant
  2. Parallel
  3. Decreasing amplitude
31
Q

What is this artifact?

A

Reverb

32
Q

How does pseudo mass reverberation occur?

A

A beam striking a curved Specular reflector, and then hitting other curved interfaces causes an indirect path back to the probe

33
Q

How is pseudomass reverberation interpreted

A

The signal is interpreted as part of another beam path

34
Q

What is an example of pseudomass reverberation?

A

Multi path/ mirror image artifacts

35
Q

What is one situation where we see pseudomass artifacts?

A

With extremely full bladders

36
Q

What is comet tail reverberation?

A

Internal reverberation that occurs in dense, highly reflective objects

37
Q

What does comet tail reverberation artifacts look like?

A

Multiple echoes, equal distance apart

38
Q

What are things that result in comet tail artifacts?

A
  1. IUCD
  2. Surgical clips
  3. Shotgun pellets
39
Q

What is this an image of?

A

IUCD with reverberation artifact

40
Q

In terms of ring down reverberation, resonance artifacts are created by what?

A

Gas bubbles

41
Q

Bubbles in resonance artifacts form what?

A

Fluid bugles

42
Q

When the fluid bugles of resonance artifacts oscillate what happens?

A

It causes the liquid to vibrate and sends a continuous signal of decreasing amplitude back to the transducer.

43
Q

The fluid bugle of resonance artifacts, what determines the frequency used? What does this mean?

A

The fluid bugle resonates at a frequency determined by its size, therefore independent of original transducer frequency

44
Q

What is a ring down frequency similar in appearance to?

A

Comet tail

45
Q

What is another way of thinking of attenuation?

A

Shadowing

46
Q

Sound does what as it travels through a medium?

A

It attenuates

47
Q

What kind of attenuating structure is bone?

A

Bone is extremely dense and attenuate a lot of sound

48
Q

Having a shadow behind an echogenic focus means what?

A

It is calcified

49
Q

What is enhancement?

A

Opposite of shadow

50
Q

How does enhancement happen?

A

Increased amplitude is seen behind fluid filled structures

51
Q

How does fluid attenuate?

A

Fluid attenuates very little sound

52
Q

Why is enhancement useful?

A

To determine whether a mass contains fluid

53
Q

An anechoic mass without posterior enhancement is what?

A

Not a cyst

54
Q

What are side lobe artifacts?

A

Multiple side beams of lower intensity that emanate from the transducer, surrounding the main beam.

55
Q

Side lobes happen because of what?

A

Multiple side beams scattering after hitting a Specular reflector

56
Q

What are side lobes depending on?

A

Beam angle and intensity

57
Q

What is this an example of?

A

Side lobe artifact

58
Q

How does a slice thickest artifact happen?

A

When a cystic structure is off axis of the beam, and an averaging effect occurs between the cyst and the surrounding tissue, cause the cyst to fill in with echoes

59
Q

How doe we reduce artifacts? 4

A
  1. Appropriate gain settings
  2. Proper transducer settings
  3. Proper focal zones in correct area
  4. Change probe position/ scan plane

DMST 315 OBGYN 3 (21 decks)

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