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Ultrasound Physics > Chapter 12 - Two Dimensional Imaging > Flashcards

Chapter 12 - Two Dimensional Imaging Flashcards

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
What type of beam focusing is used in linear phased array transducers?
Electronic, transmit, and receive focusing
26
What happens if an element in a linear phased array transducer is damaged?
There will be inconsistent beam steering snd focusing.
27
Phased array always means ____ or ____.
Adjustable or multi-focus.
28
In phased array transducers, ____ elements are fired to create each sound beam.
ALL
29
____ is small time delays between the excitation pulses to each transducer element within the array.
Phasing
30
Phasing controls ____ and ____.
Steering and focusing.
31
What is the directing of the sound beam in different directions from the transducer?
Beam steering
32
The ____ of the electrical spike line determines the direction of propagation of the sound beam.
Slope
33
Any time the electrical spike line has a ____, the sound beam is being ____.
Slope; steered
34
The sonographer can control steering by changing the ____ ____.
Sector width
35
The electronics within the ultrasound system that create these patterns is called the ____ ____.
Beam former
36
The slope of the electrical spike line determines the direction of the ____ of the sound beam.
Propagation
37
In a linear phased array transducer, when the electrical spike pattern is ____, an unfocused sound beam is created.
Straight
38
In a linear phased array transducer, when the electrical spike pattern is ____, a focused sound beam is created.
Curved
39
In a linear phased array transducer, when the outer crystals are excited earlier than the inner crystals, the curved pattern created a ____ sound beam.
Focused (more curved = shallower focus; less curve = deeper focus)
40
In a linear phased array transducer, a sound beam can be ____ and ____ at the same time.
Steered and focused
41
A ____ beam has NO application in diagnostic imaging.
Defocused (outward or D-shaped pattern)
42
Multi-focusing created a more ____ image.
Accurate
43
To create an image with multiple foci at different depths, the ultrasound system must send multiple ____ ____ down each scan line.
Sound beams
44
Dynamic receive focusing is focusing during ____.
Reception
45
A more accurate image can be created when the ultrasound receiver introduces ____ ____ to some of the electrical signals during reception.
Time delays
46
What is the shape of the element in an annular phased array transducer?
Circular disc-shaped
47
How many active elements are in an annular phased array transducer?
Multiple; bulls eye
48
What is the image shape created by an annular phased array transducer?
A wide fan or sector shape / \ / \ / \
49
What type of beam steering is used in annular phased array transducers?
Mechanical (physically moves)
50
What type of beam focusing is used in annular phased array transducers?
Electronic; multi-focus
51
What happens if an element in a annular phased array transducer is damaged?
Horizontal band dropout
52
The inner crystal of an annular phased array transducer is the ____ so it creates the ____ focus.
Smallest; shallowest
53
Each successively larger element in an annular phased array transducer will have a ____ focus.
Deeper
54
In an annular phased array transducer, only information from the ____ is stored.
Focus
55
What is the element shape used in a linear sequential array transducer?
Rectangular; large footprint
56
How many active elements are in a linear sequential array transducer?
120-250
57
What is the image shape created by a linear sequential array transducer?
Rectangular or parallellogram
58
What type of beam steering is used in a linear sequential array transducer?
electronic or phased
59
What type of beam focusing is used in a linear sequential array transducer?
- Old style: fixed with a lens or curved element - Modern style: electronic with transmit and receive focusing
60
What happens if an element in a linear sequential array transducer is damaged?
Vertical band dropout
61
When groups of elements are fired in a specific pattern.
Sequential
62
With ____ ____ arrays, some but not all of the crystals are fired simultaneously to create each sound beam.
Linear sequential
63
In linear sequential array transducers, the sound beams are ____ to each other and directed ____ ____.
Parallel; straight ahead
64
What is the shape of the element in a curvilinear array transducer?
Rectangular and curved; large footprint
65
How many active elements are in a curvilinear array transducer?
120-250
66
What is the shape of the image produced by a curvilinear array transducer?
Sector with a curved top
67
What type of beam steering is used in a curvilinear array transducer?
Naturally curved probe foot
68
What type of beam focusing is used in a curvilinear array transducer?
Electronic; transmit and receive focusing
69
What happens if an element in a curvilinear array transducer is damaged?
Vertical band dropout
70
A vector array is a combination of ____ ____ and ____ ____ ____ technologies.
Linear sequential and linear phased array
71
What is the shape of the element used in a vector array transducer?
Rectangular; small footprint
72
How many active elements are in a vector array transducer?
120-250
73
What is the image shape produced by a vector array transducer?
Trapezoidal (flat at top, curved at bottom)
74
What type of beam steering is used with vector array transducers?
Electronic or phased
75
What type of beam focusing is used with vector array transducers?
Electronic; transmit and receive focusing
76
What happens if an element in a vector array transducer is damaged?
Vertical band dropout
77
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?
Side lobes
78
What are the additional areas of sound energy that extend outside of the main beam?
Grating lobes
79
What are side lobes created by?
Single element transducers
80
What are grating globes created by?
Array transducers
81
____ is the use of nonuniform voltages to excite the elements.
Apodization
82
____ reduces side lobes and grating lobes.
Apodization
83
____ is the dividing of each element into a group of smaller elements.
Subdicing
84
What are the two things that subdicing does?
Weakens grating lobes and improves focusing.
85
What is the technique used to make a sound beam narrow over a greater range of depths?
Dynamic aperture/variable aperture

Ultrasound Physics (11 decks)

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