SPI 3 Flashcards
1
Q
Far field
A
Region distal to focal point where sound beam diverges
Intensity of beam more uniform
2
Q
Far field relationship
A
Inversely related to operating frequency and diameter of element
(Increasing frequency decreases angle of divergence)
3
Q
Focal length determined by
A
Operating frequency and diameter of element
4
Q
Focal length directly related to
A
Operating frequency and diameter of element
5
Q
Focal length inversely related to
A
Divergence of beam in far field
6
Q
Focal point is also called
A
Focus
Area of maximum intensity in the beam
7
Q
Focal Zone is located
A
1/2 in near field
1/2 in far field
8
Q
Near field length directly related to
A
Frequency of the transducer and diameter of element
9
Q
Focusing if the sound beam improves
A
Lateral resolution
10
Q
Focusing accomplished where?
A
Within near field
11
Q
Focusing creates
A
A narrower sound beam over a specific area
12
Q
Beam diameter in near field does what toward the focal point
A
Decreases in size
13
Q
Beam diameter in far field
A
Increases in size after focal point
14
Q
Increasing frequency or diameter of the element
A
Produces a narrower beam
Longer focal length
Less divergence in far field
15
Q
External focus
A
Lens placed in front of crystal to focus sound beam
16
Q
Internal focus
A
Beam diameter is reduced in the focal point
Piezoelectric element shaped concavely to focus the sound beam
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
18
Q
Axial Resolution characteristics
A
Does not vary with distance
Always better than lateral resolution
Improves with transducer dampening
19
Q
Axial resolution is equal to
A
1/2 SPL
Smaller is better
20
Q
Axial resolution is directly related to?
A
Frequency
21
Q
Axial resolution is inversely related to
A
SPL and depth
22
Q
Contrast resolution
A
Ability to differentiate. Between echoes of slightly different amplitude
23
Q
High contrast
A
Fewer shades of gray
24
Q
Low contrast
A
More shares of gray
25
Contrast resolution is directly related to
Axial and lateral resolution
26
Elevational resolution is related to
Beam width
| Thinner slice thickness produces better image quality
27
Lateral resolution improves with
Focusing
28
Lateral resolution is directly related to
Beam diameter, frequency, focus, and distance
29
Spatial resolution
Ability to see detail on image
30
Spatial resolution is directly related to
Number of scan lines
31
Spatial resolution is indirectly related to
Temporal resolution
32
Temporal resolution
Ability to position moving structures precisely
Ability to separate two points in time
33
Temporal resolution determined by
Frame rate
34
Temporal resolution is directly related to
Frame rate
35
Temporal resolution is indirectly related to
Number of focal zones depth and spatial resolution
36
Optimizing axial resolution
Increase frequency
Increase focal zones
Decrease imaging depth
37
Optimizing contrast resolution
Increase compression (dynamic range)
Increase frequency
Decrease beam width
Post process mapping
38
Optimizing lateral resolution
Proper focal placement
Decrease beam width
Decrease depth
39
Optimizing temporal resolution
Decrease focal zones
Decrease depth
Decrease beam width
Decrease persistence
40
Artifact
Anything not properly indicative of anatomy or motion imaged
41
Binary number
Group of bits
42
Bit
Binary digit; smallest amount of computer memory
43
Byte
Group of 8 bits of computer memory
44
Channel
An independent signal path consisting of a transducer element delay and other electronic components
45
Code excitation
Series of pulses and gaps allowing multiple focal zones and harmonic frequencies
46
Comet tail
Series of closely spaced reverberation echoes behind a strong reflector
47
Dynamic range
Ratio of the largest to the smallest amplitude that the ultrasound system can handle
48
Edge shadow
Loss of intensity from bending of the sound beam at a curved surface
49
Enhancement
Increase in reflection amplitude from structures that lie behind a weakly attenuating structure
50
Field of view
Displayed image of of returning echoes
51
Frame rate
The number of complete scans (images) displayed per second
52
Gain
Ratio of amplifier output to input of electric power
53
Grating lobes
Secondary sound beams produced by a multi element transducer
54
Line density
Number of scan lines per frame; scan line density
55
Matrix
Denotes the rows and columns of pixels in a digital image
56
Mirror image
Artifact gray scale, color Flow, or Doppler signal appearing on the opposite side of a strong reflector
57
Multipath
Path toward and away from a reflector are different
58
Noise
Disturbance that reduces the clarity of the signal
59
Nyquist limit
Minimum number of samples required to avoid aliasing; Doppler shift frequency above which aliasing occurs
60
Pixel
Smallest portion of digital image
61
Pixel density
Number of picture elements per inch
62
Pulse repetition frequency
Number of voltage pulses sent to transducer each second
63
Pulse repetition period
time from beginning of one voltage pulse to the start of the next voltage pulse
64
RAM (random-access memory)
allows access of stored data in an unsystematic order
65
Range ambiguity
Produces when echoes are placed too superficially because a second pulse was emitted before all reflections have returned from the first pulse
66
ROM (read-only memory)
Stored data cannot be modified
67
Real time imaging
Two dimensional imaging of the motion of moving structures
68
Reflection
Portion of sound reflected from the boundary of a medium
69
Refraction
Change of sound direction on passing from one medium to another
70
Reverberation
Multiple reflections between a structure and the transducer or within a structure
71
Scattering
Redirection of sound in several directions on encountering a rough surface
72
Shadowing
Reduction of reflective amplitude from reflectors that lie behind a strongly reflecting or attenuating structure
73
Signal to noise ratio
Comparison of meaningful information in an image (signal) to the amount of signal disturbance (noise)
74
Spatial compounding
Averaging of frames that view anatomy from different angles
75
Specular
Large flat smooth surface
76
Voxel
Smallest distinguishable part of a 3-D image
77
A-Mode
Amplitude mode
Y axis- amplitude
X-axis- distance
Single sound beam one dimentional
78
B-Mode
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
M-mode
Motion mode
Y axis- reflector depth
X axis- time
80
Advantages of real time imaging
Rapid location of anatomy
Movement can be observed
Structures or vessels can be followed
81
Limitations of real time imaging
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
Field of View is directly related to
PRF
83
Field of view is inversely related to
Frame rate and temporal resolution
84
Field of view is adjusted using
Depth and region of interest settings
85
Frame rate determines
Temporal resolution
86
Frame rate is determined by
Propagation speed of the medium and imaging depth
87
Frame rate is proportional to
PRF
88
Frame rate is inversely related to
Number of focal zones used, imaging depth, and lines per frame (beam width)
89
Frame rate adjusted by
Using depth and PRF settings
90
Line density is directly related to
PRF and spatial resolution
91
Line density inversely related to
frame rate and temporal resolution
92
Max imaging depth dependent on
Frame rate, number of lines per frame, and number of focal zones used
93
Pulse repetition frequency inversely related to
Frequency and depth
94
Pulse repetition frequency indirectly adjusted by
Imaging depth setting
95
Coded excitation improves
Contrast, axial, and spatial resolution
96
Coded excitation occurs where
Pulser
97
4-D imaging
Real time presentation of 3-D image
98
Harmonic frequencies relationships
Improves lateral resolution
Decreases contrast resolution
Reduces grating lobes
99
Harmonics frequency generated
At a deeper imaging depth (reduces reverberation)
And in the highest intensity and narrowest portion of the beam
100
Multifocal imaging directly related to
Lateral resolution and PRF
101
Multifocal imaging inversely related to
Frame rate and temporal resolution
102
Spatial compounding does what
Improves visualization of structures beneath a highly attenuating structure and smooths specular surfaces
103
Spatial compounding reduces
Speckle and noise
104
Spatial compounding uses
Phasing to interrogate the structures more than once
105
Functions of pulses echo instrumentation
Prepare and transmit electronic signals to the transducer to produce a sound wave
Receive electronic signals from reflections
Process reflected info for display
106
Power
Output control
Controls the amplitude of transmitted sound beam and the amplitude of the received echoes
107
Power is directly related to
Signal to noise ratio and the intensity of acoustic exposure of patient
108
Acoustic exposure measured by
Mechanical index and thermal index
109
Master synchronizer
Instructs pulser to send electrical signal to transducer
Coordinates all the components of the US system
Manager of US system
110
Pulser (transmitter)
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
Pulser determines what?
PRF PRP and pulse amplitude
112
Digital beam former
Part of pulser
| Determines firing delay for array systems
113
What happens to beam former during reception
Establishes time delays used in dynamic focusing
114
Advantages of beam former
Software programming and extremely stable with wide range of frequencies
115
Receiver
Amplifies and modifies echo information returning from the transducer
116
5 functions of receiver
```
Amplification
Compression
Compensation
Demodulation
Rejection
```
117
Amplification
dB
| Increases small electric voltages received from the transducer to a level suitable for processing
118
Amplification adjusted how?
Using overall gain setting
119
Compensation
TGC
| compensates for the loss of echo strength caused by the depth of the reflector
120
Areas of compensation
```
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
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