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DSM PHY > SPI 3 > Flashcards

SPI 3 Flashcards

1
Q

Far field

A

Region distal to focal point where sound beam diverges

Intensity of beam more uniform

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2
Q

Far field relationship

A

Inversely related to operating frequency and diameter of element

(Increasing frequency decreases angle of divergence)

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3
Q

Focal length determined by

A

Operating frequency and diameter of element

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4
Q

Focal length directly related to

A

Operating frequency and diameter of element

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5
Q

Focal length inversely related to

A

Divergence of beam in far field

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6
Q

Focal point is also called

A

Focus

Area of maximum intensity in the beam

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7
Q

Focal Zone is located

A

1/2 in near field

1/2 in far field

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8
Q

Near field length directly related to

A

Frequency of the transducer and diameter of element

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9
Q

Focusing if the sound beam improves

A

Lateral resolution

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10
Q

Focusing accomplished where?

A

Within near field

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11
Q

Focusing creates

A

A narrower sound beam over a specific area

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12
Q

Beam diameter in near field does what toward the focal point

A

Decreases in size

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13
Q

Beam diameter in far field

A

Increases in size after focal point

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14
Q

Increasing frequency or diameter of the element

A

Produces a narrower beam
Longer focal length
Less divergence in far field

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15
Q

External focus

A

Lens placed in front of crystal to focus sound beam

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16
Q

Internal focus

A

Beam diameter is reduced in the focal point

Piezoelectric element shaped concavely to focus the sound beam

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17
Q

Steering sound beam

A

Created by beam former
Used to sweep sound wave over specific area
System alters electronic excitation of elements steering beam in various directions
Returning echoes delayed

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18
Q

Axial Resolution characteristics

A

Does not vary with distance
Always better than lateral resolution
Improves with transducer dampening

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19
Q

Axial resolution is equal to

A

1/2 SPL

Smaller is better

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20
Q

Axial resolution is directly related to?

A

Frequency

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21
Q

Axial resolution is inversely related to

A

SPL and depth

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22
Q

Contrast resolution

A

Ability to differentiate. Between echoes of slightly different amplitude

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23
Q

High contrast

A

Fewer shades of gray

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24
Q

Low contrast

A

More shares of gray

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25
Q

Contrast resolution is directly related to

A

Axial and lateral resolution

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26
Q

Elevational resolution is related to

A

Beam width

Thinner slice thickness produces better image quality

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27
Q

Lateral resolution improves with

A

Focusing

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28
Q

Lateral resolution is directly related to

A

Beam diameter, frequency, focus, and distance

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29
Q

Spatial resolution

A

Ability to see detail on image

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30
Q

Spatial resolution is directly related to

A

Number of scan lines

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31
Q

Spatial resolution is indirectly related to

A

Temporal resolution

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32
Q

Temporal resolution

A

Ability to position moving structures precisely

Ability to separate two points in time

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33
Q

Temporal resolution determined by

A

Frame rate

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34
Q

Temporal resolution is directly related to

A

Frame rate

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35
Q

Temporal resolution is indirectly related to

A

Number of focal zones depth and spatial resolution

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36
Q

Optimizing axial resolution

A

Increase frequency

Increase focal zones

Decrease imaging depth

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37
Q

Optimizing contrast resolution

A

Increase compression (dynamic range)

Increase frequency

Decrease beam width

Post process mapping

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38
Q

Optimizing lateral resolution

A

Proper focal placement

Decrease beam width

Decrease depth

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39
Q

Optimizing temporal resolution

A

Decrease focal zones

Decrease depth

Decrease beam width

Decrease persistence

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40
Q

Artifact

A

Anything not properly indicative of anatomy or motion imaged

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41
Q

Binary number

A

Group of bits

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42
Q

Bit

A

Binary digit; smallest amount of computer memory

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43
Q

Byte

A

Group of 8 bits of computer memory

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44
Q

Channel

A

An independent signal path consisting of a transducer element delay and other electronic components

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45
Q

Code excitation

A

Series of pulses and gaps allowing multiple focal zones and harmonic frequencies

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46
Q

Comet tail

A

Series of closely spaced reverberation echoes behind a strong reflector

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47
Q

Dynamic range

A

Ratio of the largest to the smallest amplitude that the ultrasound system can handle

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48
Q

Edge shadow

A

Loss of intensity from bending of the sound beam at a curved surface

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49
Q

Enhancement

A

Increase in reflection amplitude from structures that lie behind a weakly attenuating structure

50
Q

Field of view

A

Displayed image of of returning echoes

51
Q

Frame rate

A

The number of complete scans (images) displayed per second

52
Q

Gain

A

Ratio of amplifier output to input of electric power

53
Q

Grating lobes

A

Secondary sound beams produced by a multi element transducer

54
Q

Line density

A

Number of scan lines per frame; scan line density

55
Q

Matrix

A

Denotes the rows and columns of pixels in a digital image

56
Q

Mirror image

A

Artifact gray scale, color Flow, or Doppler signal appearing on the opposite side of a strong reflector

57
Q

Multipath

A

Path toward and away from a reflector are different

58
Q

Noise

A

Disturbance that reduces the clarity of the signal

59
Q

Nyquist limit

A

Minimum number of samples required to avoid aliasing; Doppler shift frequency above which aliasing occurs

60
Q

Pixel

A

Smallest portion of digital image

61
Q

Pixel density

A

Number of picture elements per inch

62
Q

Pulse repetition frequency

A

Number of voltage pulses sent to transducer each second

63
Q

Pulse repetition period

A

time from beginning of one voltage pulse to the start of the next voltage pulse

64
Q

RAM (random-access memory)

A

allows access of stored data in an unsystematic order

65
Q

Range ambiguity

A

Produces when echoes are placed too superficially because a second pulse was emitted before all reflections have returned from the first pulse

66
Q

ROM (read-only memory)

A

Stored data cannot be modified

67
Q

Real time imaging

A

Two dimensional imaging of the motion of moving structures

68
Q

Reflection

A

Portion of sound reflected from the boundary of a medium

69
Q

Refraction

A

Change of sound direction on passing from one medium to another

70
Q

Reverberation

A

Multiple reflections between a structure and the transducer or within a structure

71
Q

Scattering

A

Redirection of sound in several directions on encountering a rough surface

72
Q

Shadowing

A

Reduction of reflective amplitude from reflectors that lie behind a strongly reflecting or attenuating structure

73
Q

Signal to noise ratio

A

Comparison of meaningful information in an image (signal) to the amount of signal disturbance (noise)

74
Q

Spatial compounding

A

Averaging of frames that view anatomy from different angles

75
Q

Specular

A

Large flat smooth surface

76
Q

Voxel

A

Smallest distinguishable part of a 3-D image

77
Q

A-Mode

A

Amplitude mode
Y axis- amplitude
X-axis- distance

Single sound beam one dimentional

78
Q

B-Mode

A

Brightness mode
2-D image cross-sectional using multiple sound beams
Displays strength of returning echoes as pixels in various shades of gray
Y-axis- depth
X-axis- side to side or superior to inferior aspects of body
Stronger the reflection brighter the pixel

79
Q

M-mode

A

Motion mode
Y axis- reflector depth
X axis- time

80
Q

Advantages of real time imaging

A

Rapid location of anatomy

Movement can be observed

Structures or vessels can be followed

81
Q

Limitations of real time imaging

A

Penetration depth is limited by propagation speed of the medium

Exact imaging plane cannot be systematically reproduced

Measurement of structures larger than the field of view is estimated

82
Q

Field of View is directly related to

A

PRF

83
Q

Field of view is inversely related to

A

Frame rate and temporal resolution

84
Q

Field of view is adjusted using

A

Depth and region of interest settings

85
Q

Frame rate determines

A

Temporal resolution

86
Q

Frame rate is determined by

A

Propagation speed of the medium and imaging depth

87
Q

Frame rate is proportional to

A

PRF

88
Q

Frame rate is inversely related to

A

Number of focal zones used, imaging depth, and lines per frame (beam width)

89
Q

Frame rate adjusted by

A

Using depth and PRF settings

90
Q

Line density is directly related to

A

PRF and spatial resolution

91
Q

Line density inversely related to

A

frame rate and temporal resolution

92
Q

Max imaging depth dependent on

A

Frame rate, number of lines per frame, and number of focal zones used

93
Q

Pulse repetition frequency inversely related to

A

Frequency and depth

94
Q

Pulse repetition frequency indirectly adjusted by

A

Imaging depth setting

95
Q

Coded excitation improves

A

Contrast, axial, and spatial resolution

96
Q

Coded excitation occurs where

A

Pulser

97
Q

4-D imaging

A

Real time presentation of 3-D image

98
Q

Harmonic frequencies relationships

A

Improves lateral resolution
Decreases contrast resolution
Reduces grating lobes

99
Q

Harmonics frequency generated

A

At a deeper imaging depth (reduces reverberation)

And in the highest intensity and narrowest portion of the beam

100
Q

Multifocal imaging directly related to

A

Lateral resolution and PRF

101
Q

Multifocal imaging inversely related to

A

Frame rate and temporal resolution

102
Q

Spatial compounding does what

A

Improves visualization of structures beneath a highly attenuating structure and smooths specular surfaces

103
Q

Spatial compounding reduces

A

Speckle and noise

104
Q

Spatial compounding uses

A

Phasing to interrogate the structures more than once

105
Q

Functions of pulses echo instrumentation

A

Prepare and transmit electronic signals to the transducer to produce a sound wave

Receive electronic signals from reflections

Process reflected info for display

106
Q

Power

A

Output control

Controls the amplitude of transmitted sound beam and the amplitude of the received echoes

107
Q

Power is directly related to

A

Signal to noise ratio and the intensity of acoustic exposure of patient

108
Q

Acoustic exposure measured by

A

Mechanical index and thermal index

109
Q

Master synchronizer

A

Instructs pulser to send electrical signal to transducer
Coordinates all the components of the US system
Manager of US system

110
Q

Pulser (transmitter)

A

Generates pulses to crystal producing pulsed US waves
Drives transducer through pulse delays with one voltage pulse per scan line
Adjusts PRF for imaging depth
Communicates with receiver the moment the crystal is excited to help determine distance to reflector

111
Q

Pulser determines what?

A

PRF PRP and pulse amplitude

112
Q

Digital beam former

A

Part of pulser

Determines firing delay for array systems

113
Q

What happens to beam former during reception

A

Establishes time delays used in dynamic focusing

114
Q

Advantages of beam former

A

Software programming and extremely stable with wide range of frequencies

115
Q

Receiver

A

Amplifies and modifies echo information returning from the transducer

116
Q

5 functions of receiver

A 
Amplification
Compression
Compensation
Demodulation 
Rejection
117
Q

Amplification

A

dB

Increases small electric voltages received from the transducer to a level suitable for processing

118
Q

Amplification adjusted how?

A

Using overall gain setting

119
Q

Compensation

A

TGC

compensates for the loss of echo strength caused by the depth of the reflector

120
Q

Areas of compensation

A 
Near field- minimum amplification
Delay- depth where compensation begins
Slope-region for depth compensation
Knee-deepest region attenuation compensation can occur
Far field- max amplification

DSM PHY (14 decks)

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