Quiz 4 Flashcards
(125 cards)
1
Q
What is axial resolution?
A
Two structures that are close together when the structures are parallel to the sound beam
2
Q
What are the units for axial resolution?
A
mm
3
Q
What is axial resolution determined by?
A
SPL
(Source and medium)
4
Q
What improves axial resolution?
A
Shorter pulse lengths
Shorter duration
Higher frequencies
Less cycles per pulse
5
Q
What are other names for axial resolution?
A
(LARRD)
longitudinal
Axial
Range
Radial
Depth
6
Q
Is axial resolution adjustable?
A
No
7
Q
What creates a short pulse?
A
Less ringing
High frequencies
8
Q
What is the formula for axial resolution in soft tissue?
A
Axial resolution = 0.77 TIMES #of cycles in pulse DIVIDED BY frequency
9
Q
What is lateral resolution?
A
Two structures that are very close together are perpendicular to the sound beam
10
Q
What are the units for lateral resolution?
A
mm
11
Q
What is lateral resolution determined by?
A
Width of sound beam
12
Q
What are the other names for lateral resolution?
A
(LATA)
Lateral
Angular
Transverse
Azimuthal
13
Q
What happens to lateral resolution as the sound goes deeper?
A
Worsens or decreases
14
Q
Lateral resolution is best at what point on the sound beam?
A
The focus
15
Q
Lateral resolution = ?
A
Beam diameter
16
Q
Axial resolution has ____ pulses in the _______field and _____ pulses in the ______ field
A
Short pulses in near field
Short pulses in far field
17
Q
Lateral resolution has a______ diameter crystal in the _____ field and a_____ diameter in the _____field with a _____ frequency transducer.
A
Small diameter crystal in the near field and a large diameter in the far field with a high frequency transducer.
18
Q
Is axial or lateral better for resolution?
A
Axial
19
Q
High frequency and less beam divergence in far field is better because of what resolution?
A
Lateral resolution
20
Q
High frequency and short pulses for entire image are better in what resolution?
A
Axial
21
Q
What are the 3 methods for focusing?
A
External focusing
Internal focusing
Phased array focusing
22
Q
What does external focus use and what type of focus?
A
A lens
Fixed focus
23
Q
What does internal focus use and what type of focus?
A
Curved active element (PZT)
Fixed focus
24
Q
What type of focus do phased array use?
A
Electronic
25
What are the effects of focusing?
-smaller beam diameter in near field
-focal depth is shallow
-increased beam diameter in far zone
-focal zone is smaller
26
CW frequency is determined by?
Frequency of electronic signal
27
PW wave is determined by ?
Thickness of PZT
Speed of sound in PZT
28
Focal length is determined by?
-Diameter of PZT
-Frequency
29
Beam divergence is determined by?
-Diameter of PZT
-Frequency
30
What is A-mode?
Series of upward spikes of different amplitudes
31
What does the X-axis represent in A-mode?
Depth
32
What the Y-axis represent in A-mode?
Amplitude
33
In A-mode….
Strong echos create _____ spikes and weak reflections create ____spikes?
Tall spikes
Short spikes
34
What is B-mode?
Line of does that vary in brightness
35
What is the X-axis in B-mode?
Depth
36
What is the Z-axis in B-mode?
Amplitude (strength)
37
What is the main purpose for B-mode?
Describes gray scale on an image
(B-mode is the basis for all grayscale imaging)
38
Dark gray dots mean what in B-mode?
Weak reflections
39
Brighter gray dots in B-mode mean?
Strong reflections
40
What is M-mode?
Group of horizontal wavy lines
41
What does M-mode show?
Shows motion of structures over time
42
What modality(s) are non-scanned?
A and M mode
43
What modality is M-mode used in?
Echo and OB
44
What does the X-axis represent in M-mode?
Time
45
What does the Y-axis represent in M-mode
Depth
46
Which modality provides 2D images?
B-mode
47
What are challenges of 2D imaging?
-Sound traveling in a straight line
-Sound beams must be narrow to create good lateral resolution
48
What is a Pedof transducer and what is it used for?
-non imaging
-used for CW doppler
49
How many crystals and what shape does a pedof transducer use?
2 crystals
Semi circular
50
What happens to the crystal in a Pedof transducer when it is damaged?
No signal received or transmitted
51
What type of steering does a Pedof transducer use?
Manual
52
What type of focusing does a Pedof transducer use?
Fixed focus
53
Where are Pedof transducers used in ultrasound?
Echo
54
What image shape do Mechanical transducers have?
Sector/fan
55
What is the crystal shape and how many crystals are used in a Mechanical transducer?
Circular shape
Single crystal
56
What is the beam steering in a mechanical sector transducer ?
Mechanical
57
How does the beam focus the crystal in a Mechanical transducer?
-Fixed
-internal focusing that uses a curved element
-external focusing that uses an acoustic lens
58
What happens to the crystal when it malfunctions in a Mechanical transducer?
Entire image is lost
59
Where are Mechanical transducers used?
Echo
60
What is a disadvantage to using a Mechanical transducer?
They leak oil and lose air
61
What are transducer Arrays?
-Multiple active elements that are attached to a wire and have their own electronics.
-Each element is separated from other elements and produce an electronic signal from the returned echos to send them to the systems receiver
62
Arrays consist of?
Multiple active elements attached to a wire, and produce its own electronic signals from returned echos and send them to the receiver
63
What image shape does a Mechanical Annular Array have?
Sector shape
64
How many crystals and what shape does a Mechanical Annular Array have?
Concentric(many)
Circular
65
When a crystal is damaged in a Mechanical Annular Array what does it look like?
A horizontal band across the image
66
What type of steering does a Mechanical Annular Array have?
Mechanical (motor)
67
What type of focus is used in a Mechanical Annular Array?
And how ?
Fixed focus by firing each concentric circle in order to have a focus at different depths
68
What is an advantage to using Mechanical Annular Array?
Great lateral resolution
69
What is a disadvantage to using Mechanical Annular Array?
Poor temporal resolution
Oily and lose air
70
What image shape does a Linear Switched Array have?
Rectangle
71
What crystal shape and how many crystals are in a Linear Switched Array?
Rectangle
200 crystals
72
What happens to a Linear Switched Array when it is damaged?
Vertical drop out
(gap in the image)
73
What type of focus is used in a Linear Switched Array?
Fixed
(Internal/external)
74
Where are Linear Switched Arrays used?
Vascular and some general
75
How many crystals do Linear Phased Arrays have? And what shape?
100-300
Rectangle
76
What image shape do Linear Phased Arrays have?
Sector / fan
77
What is the beam steering for Linear Phased Array?
Electronic
(Steered in different directions)
78
What is the beam focusing for Linear Phased Array?
-Electronic phasing
79
What is the advantage to Linear Phased Arrays?
Multi focusing
(the sonographer can choose the depth and how much focus there is)
80
What happens to a Linear Phased Arrays transducer when the crystal is damaged?
Issues with steering and focusing
81
Linear phased array
82
What is dynamic receiving focusing?
allow for time delays of the received echos which allows for focusing at many depths to create clear images
(Used by array transducers)
83
What is the crystal shape of Linear Sequential Array? And how many crystals?
Rectangular
125-250
84
What is the image shape of a Linear Sequential Array?
Rectangular (wide scan)
85
What is the beam steering for Linear Sequential Arrays?
Electronic
86
What is the beam focusing for Linear Sequential Arrays?
Electronic
87
What happens to the crystal in Linear Sequential Arrays if damaged?
Only the portion of the image directly below the damaged crystal will be missing
88
Why are linear sequential arrays good?
They use multiple side by side elements that create better direction
Good lateral resolution
89
What type of transducer is this?
Linear Sequential Array
90
What type of transducer is this?
Convex, curved (curvilinear) array
91
How many crystals are in a convex/curved array? And what shape?
125-250
Rectangular pattern
92
What is the image shape in convex / curved array?
Blunt sector shaped
93
What is the beam steering for a convex,curved array?
Electronic
94
What is the beam focusing for Convex, curved arrays?
-Electronic
95
What happens to the crystal if it is damaged in a convex, curved array?
Only the part of the image below the damaged crystal will be missing
96
What is the combo for Vector arrays?
Part linear sequential and linear phased
97
How many crystals are in a vector array?
120-250 formed in a line
98
Why do Vector arrays use a 1 1/2 dimensional format?
It provides better elevational resolution
99
What is the image shape of a Vector array?
Trapezoid with a flat top
100
What is the beam steering for a vector array?
Electronic
101
What is the beam focusing for Vector arrays?
-Electronic focusing
(Transmit and receive phased delays)
-Provides good lateral resolution
102
What happens to a vector array when a crystal is damaged?
Poor steering and focusing
103
What type of transducer is this?
Vector array
104
How is slice thickness measured?
Perpendicular to the image plane (above to below)
105
Why is Slice Thickness Resolution important?
It affects the accuracy and quality of the image.
106
How does a thin beam affect image quality?
A thin beam can differentiate better between structures, resulting in a more accurate and higher quality image.
107
What happens when a beam is thick?
It may include structures that are above or below the beam and place them in the image.
108
Fill in the blank: A _______ beam would be able to differentiate better between structures.
[thin]
109
How many crystals do 1 1/2D arrays use?
100wide
7tall
110
What is another name for 3D imaging?
Volume imaging
111
What does 3D imaging use?
2D array transducer with crystals arranged in a checkerboard pattern
112
How is 3D imaging focused?
Electronically
113
What is 3D rendering?
Takes the data from scanning to create 3D images, makes it more realistic
114
What are side lobes?
Occurs with single element transducers
Off axis side beams that create artifacts and poor lateral resolution
115
What are grating lobes?
Occur with array transducers that cause artifacts and decrease lateral resolution
116
What is apodization and how is it achieved?
Reduced the intensity of side and grating lobes
Different strengths of voltages are applied
117
What is subdicing?
Reduces grating lobes by dicing up single crystals into smaller crystals called sub elements
118
What is dynamic aperture?
Keeps the sound beam narrow to improve lateral resolution
119
What type of transducers use dynamic aperture?
Array transducers
120
How do array transducers use dynamic aperture?
By changing the number of elements that are transmitted and received
121
A high Q-factor means what type of bandwidth?
Narrow bandwidth with a long SPL
122
Beams are focused by using?
Lens
Curved elements
Electronic phasing
123
Which array is best for imaging abdomen?
Curved phased array
124
How are 3D images created and in what pattern?
With 2D in checkerboard pattern
125
What is the beam steering for annular phased array?
What is the focus for annular phased array?
What is the image shape?
Mechanical
Electronic
Sector
