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Ultrasound Physics > Chapter 12 - Two Dimensional Imaging > Flashcards

Chapter 12 - Two Dimensional Imaging Flashcards

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1
Q

The use of multiple pulses to create a 2D image overcomes what two problems?

A
  1. Sound travels in a straight line
  2. Sound beams must be narrow to optimize lateral resolution
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2
Q

The ultrasound system sends a narrow ____ ____ into the body, receives a reflection, and processes and stores the data.

A

Sound pulse

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3
Q

An entire 2D image is created in less than ____ of a second.

A

1/100

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4
Q

Each transducer has five characteristics…

A
  1. Shape and # of active elements
  2. Automatic redirection of the sound beams to create an image
  3. Focusing of each sound beam
  4. Shape of the 2D image
  5. Consequences of a damaged or nonfunctional element
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5
Q

What is the shape the an element in a mechanical transducer?

A

Circular or disk-shaped (like a coin)

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6
Q

How many active elements does a mechanical transducer have?

A

One

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7
Q

What is the image shape created by a mechanical transducer?

A

Fan or sector shaped
/\
/ \
/ \

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8
Q

What type of beam steering is used in mechanical transducers?

A

Mechanical steering - the crystal is rotated with a motor, it’s moved physically.

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9
Q

What type of beam focusing is used in a mechanical transducer?

A

Fixed, mechanical, or conventional focusing

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10
Q

What are the two methods of fixed focusing?

A
  1. Internal - the use of a curved element
  2. External - the use of an acoustic lens
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11
Q

What happens if the crystal in a mechanical transducer is damaged?

A

There is only a single crystal - so the entire image would be lost.

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12
Q

Transducer ____ contain multiple active elements.

A

Arrays

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13
Q

The combination of the active element, wire, and system electronics is called a ____.

A

Channel

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14
Q

Most modern probes are ____.

A

Arrays

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15
Q

What are the three types of array transducers?

A

Linear, annular, and convex.

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16
Q

In a ____ array transducer, the active elements are arranged in a straight line.

A

Linear

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17
Q

In a ____ array transducer, the active elements are arranged as circular rings with a common center.

A

Annular

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18
Q

In a ____ array transducer, the active elements are arranged in an arched line.

A

Convex

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19
Q

Convex can also be called ____ or ____.

A

Curved or curvilinear

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20
Q

What is the element shape in a linear phased array transducer?

A

Rectangular, small footprint

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21
Q

How many active elements are in a linear phased array transducer?

A

100-300

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22
Q

How are the elements in a linear phased array transducer organized?

A

Side by side

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23
Q

What is the shape of the image created by a linear phased array transducer?

A

Fan or sector shaped
/\
/ \
/ \

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24
Q

What type of beam steering is used in linear phased array transducers?

A

Electronic or phased (no moving parts)

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25
Q

What type of beam focusing is used in linear phased array transducers?

A

Electronic, transmit, and receive focusing

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26
Q

What happens if an element in a linear phased array transducer is damaged?

A

There will be inconsistent beam steering snd focusing.

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27
Q

Phased array always means ____ or ____.

A

Adjustable or multi-focus.

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28
Q

In phased array transducers, ____ elements are fired to create each sound beam.

A

ALL

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29
Q

____ is small time delays between the excitation pulses to each transducer element within the array.

A

Phasing

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30
Q

Phasing controls ____ and ____.

A

Steering and focusing.

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31
Q

What is the directing of the sound beam in different directions from the transducer?

A

Beam steering

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32
Q

The ____ of the electrical spike line determines the direction of propagation of the sound beam.

A

Slope

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33
Q

Any time the electrical spike line has a ____, the sound beam is being ____.

A

Slope; steered

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34
Q

The sonographer can control steering by changing the ____ ____.

A

Sector width

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35
Q

The electronics within the ultrasound system that create these patterns is called the ____ ____.

A

Beam former

36
Q

The slope of the electrical spike line determines the direction of the ____ of the sound beam.

A

Propagation

37
Q

In a linear phased array transducer, when the electrical spike pattern is ____, an unfocused sound beam is created.

A

Straight

38
Q

In a linear phased array transducer, when the electrical spike pattern is ____, a focused sound beam is created.

A

Curved

39
Q

In a linear phased array transducer, when the outer crystals are excited earlier than the inner crystals, the curved pattern created a ____ sound beam.

A

Focused (more curved = shallower focus; less curve = deeper focus)

40
Q

In a linear phased array transducer, a sound beam can be ____ and ____ at the same time.

A

Steered and focused

41
Q

A ____ beam has NO application in diagnostic imaging.

A

Defocused (outward or D-shaped pattern)

42
Q

Multi-focusing created a more ____ image.

A

Accurate

43
Q

To create an image with multiple foci at different depths, the ultrasound system must send multiple ____ ____ down each scan line.

A

Sound beams

44
Q

Dynamic receive focusing is focusing during ____.

A

Reception

45
Q

A more accurate image can be created when the ultrasound receiver introduces ____ ____ to some of the electrical signals during reception.

A

Time delays

46
Q

What is the shape of the element in an annular phased array transducer?

A

Circular disc-shaped

47
Q

How many active elements are in an annular phased array transducer?

A

Multiple; bulls eye

48
Q

What is the image shape created by an annular phased array transducer?

A

A wide fan or sector shape
/ \
/ \
/ \

49
Q

What type of beam steering is used in annular phased array transducers?

A

Mechanical (physically moves)

50
Q

What type of beam focusing is used in annular phased array transducers?

A

Electronic; multi-focus

51
Q

What happens if an element in a annular phased array transducer is damaged?

A

Horizontal band dropout

52
Q

The inner crystal of an annular phased array transducer is the ____ so it creates the ____ focus.

A

Smallest; shallowest

53
Q

Each successively larger element in an annular phased array transducer will have a ____ focus.

A

Deeper

54
Q

In an annular phased array transducer, only information from the ____ is stored.

A

Focus

55
Q

What is the element shape used in a linear sequential array transducer?

A

Rectangular; large footprint

56
Q

How many active elements are in a linear sequential array transducer?

A

120-250

57
Q

What is the image shape created by a linear sequential array transducer?

A

Rectangular or parallellogram

58
Q

What type of beam steering is used in a linear sequential array transducer?

A

electronic or phased

59
Q

What type of beam focusing is used in a linear sequential array transducer?

A
  • Old style: fixed with a lens or curved element
  • Modern style: electronic with transmit and receive focusing
60
Q

What happens if an element in a linear sequential array transducer is damaged?

A

Vertical band dropout

61
Q

When groups of elements are fired in a specific pattern.

A

Sequential

62
Q

With ____ ____ arrays, some but not all of the crystals are fired simultaneously to create each sound beam.

A

Linear sequential

63
Q

In linear sequential array transducers, the sound beams are ____ to each other and directed ____ ____.

A

Parallel; straight ahead

64
Q

What is the shape of the element in a curvilinear array transducer?

A

Rectangular and curved; large footprint

65
Q

How many active elements are in a curvilinear array transducer?

A

120-250

66
Q

What is the shape of the image produced by a curvilinear array transducer?

A

Sector with a curved top

67
Q

What type of beam steering is used in a curvilinear array transducer?

A

Naturally curved probe foot

68
Q

What type of beam focusing is used in a curvilinear array transducer?

A

Electronic; transmit and receive focusing

69
Q

What happens if an element in a curvilinear array transducer is damaged?

A

Vertical band dropout

70
Q

A vector array is a combination of ____ ____ and ____ ____ ____ technologies.

A

Linear sequential and linear phased array

71
Q

What is the shape of the element used in a vector array transducer?

A

Rectangular; small footprint

72
Q

How many active elements are in a vector array transducer?

A

120-250

73
Q

What is the image shape produced by a vector array transducer?

A

Trapezoidal (flat at top, curved at bottom)

74
Q

What type of beam steering is used with vector array transducers?

A

Electronic or phased

75
Q

What type of beam focusing is used with vector array transducers?

A

Electronic; transmit and receive focusing

76
Q

What happens if an element in a vector array transducer is damaged?

A

Vertical band dropout

77
Q

What are the additional areas of sound energy at depths equal to and greater than the focal zone, that extend outside of the main beam?

A

Side lobes

78
Q

What are the additional areas of sound energy that extend outside of the main beam?

A

Grating lobes

79
Q

What are side lobes created by?

A

Single element transducers

80
Q

What are grating globes created by?

A

Array transducers

81
Q

____ is the use of nonuniform voltages to excite the elements.

A

Apodization

82
Q

____ reduces side lobes and grating lobes.

A

Apodization

83
Q

____ is the dividing of each element into a group of smaller elements.

A

Subdicing

84
Q

What are the two things that subdicing does?

A

Weakens grating lobes and improves focusing.

85
Q

What is the technique used to make a sound beam narrow over a greater range of depths?

A

Dynamic aperture/variable aperture

Ultrasound Physics (11 decks)

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