Physics Final Ch. 13-24 Flashcards
1
Q
Accuracy in time. Describes the ability to accurately show structures from instant to instant
A
temporal resolution
2
Q
Temporal resolution is determined by
A
frame rate
3
Q
System settings that affect frame rate
A
imaging depth, number of pulses per scan
4
Q
Multiple focal zones ______ the frame rate and _______ temporal resolution but has improved ______
A
decrease, diminishes, lateral resolution
5
Q
More pulses per scan line creates multiple focal zones
A
multi focus
6
Q
Allows the sonographer to control whether the low-level gray scale information within the data will appear on the displayed image
A
Reject
7
Q
Another name for reject
A
threshold or suppression
8
Q
Reject effect on the image
A
affects all low level signals on the image, regardless of their location
9
Q
Reject does not affect
A
bright echoes
10
Q
Made up of a single PZT element in the transducer, the electronics in the beam former/pulser, and the wire that connects them
A
channel
11
Q
6 major components of an ultrasound system
A
transducer, pulser/beam former, receiver, display, master synchronizer
12
Q
During transmission, transforms electrical energy into acoustic energy and during reception, transforms acoustic energy into electrical energy
A
transducer
13
Q
Creates and controls the electrical signal sent to the transducer that generates sound pulses
A
pulser/beam former
14
Q
The pulser determines the
A
amplitude, PRP, PRF
15
Q
The beam former determines the
A
firing delay patterns for phased array systems
16
Q
Transforms the electrical signals from the transducer (produced by the reflected sound) into an image to display
A
receiver
17
Q
Presents processed data-screen
A
display
18
Q
Archival of data
A
storage
19
Q
Maintains and organizes the systems components
A
master synchronizer
20
Q
Spatial resolution is also called
A
detailed resolution
21
Q
Spatial resolution is determined by
A
pixel density
22
Q
How to calculate number of gray shades
A
multiply 2 by itself the same number of times as there are bits
23
Q
Determines the range of brilliancies within the displayed image
A
contrast
24
Q
Bistable images are _____ contrast (black and white)
A
high
25
Gray scale is ______ contrast
low
26
Composed of two shades, black and white
bistable images
27
Gray scale displays _____ levels of brightness
multiple
28
Many shades of gray have better
contrast resolution
29
With sector shaped images, the scan lines separate at increasing depths. "Gaps" or "missing information" exists between the scan lines, especially as the lines spread apart
fill-in interpolation
30
Fill-in interpolation is form of
preprocessing
31
Fill-in interpolation improves
spatial resolution
32
Creation of an image from sound reflections at twice the frequency of the transmitted sound
harmonic imaging
33
Harmonic frequency sound waves arise from _______ behavior
non-linear
34
As sound waves travel in the bod, a miniscule amount of energy is converted from the fundamental frequency to the harmonic frequency
tissue harmonics
35
Tissue harmonics occurs during
transmission
36
Tissue harmonics are
non-linear
37
Series of compressions and rarefactions
sound
38
Sound travels at an _______ speed through soft tissue
uneven
39
Sound is ______ through compression and ______ through rarefaction
faster, slower
40
As an ultrasound pulse interacts with contrast agents, _______ harmonics are generated
much stronger
41
Contrast harmonics are created because the microbubbles act in a _____ manner when struck by sound waves
non-linear
42
Contrast harmonics are created during
reflection
43
Occurs when blood moves with variable velocity
pulsatile
44
In pulsatile flow, blood accelerates and decelerates as a result of
cardiac contraction
45
Pulsatile flow commonly appears in
arterial circulation
46
Occurs when blood moves at variable velocity
phasic
47
In phasic flow, blood accelerates and decelerates as a result of
respiration
48
Phasic flow commonly appears in
venous circulation
49
Occurs when a fluid moves at a constant speed or velocity
steady
50
Steady is present in
venous circulation with held inspiration/expiration
51
Characterized by chaotic flow patterns in many different directions and at many velocities
turbulent flow
52
Sound associated with turbulence is called a
murmur or bruit
53
A narrowing in the lumen of a vessel
stenosis
54
Effects stenosis has on blood flow
changes in direction, increase in velocity, post stenotic turbulence, pressure gradient
55
Velocity is highest where the vessel is
narrowest
56
The streamlines are destroyed and turbulence in the form of
eddy currents/vortices
57
Tissue vibration is called a
thrill
58
Pressure downstream from the stenosis is _____ than the pressure upstream
lower
59
Describes the relationship between velocity and pressure in a moving fluid
bernoulli's principle
60
Pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level
hydrostatic pressure
61
If blood pressure measurement is made at the level of the heart, the hydrostatic pressure is ______, no error in measured pressure
0mmHg
62
If the blood pressure measurement is made below the level of the heart, the measured blood pressure is
erroneously high
63
If the blood pressure measurement is made above the level of the heart, the measured blood pressure is
erroneously low
64
Change in frequency from motion between the sound source and the receiver
doppler shift/doppler frequency
65
The frequency of sound changes when the sound source and the receiver move
closer together or farther apart
66
Doppler shift is a principle used to measure the
velocity of blood in the circulation
67
Doppler Shift (Hz)=
reflected frequency-transmitted frequency
68
Doppler shifts are in the ______ range of frequencies
audible
69
Doppler shifts are created when transmitted sound wave strikes
moving red blood cells
70
Blood flow is moving toward the transducer
positive doppler shift
71
Blood flow is moving away from the transducer
negative doppler shift
72
Simultaneous anatomic imaging and doppler is called
duplex imaging
73
Advantage of PW doppler
being able to select the exact location where velocities are measured
74
PW doppler exact location is called
range resolution, range specicity, range specific
75
Most common error associated with doppler ultrasound
aliasing
76
An alias is a
false identity
77
The false identity in PW doppler is that very high velocities in one direction are
incorrectly displayed as going in the opposite direction
78
Does aliasing happen with CW doppler
no
79
Aliasing occurs when the doppler sampling rate (PRF) is
too low in comparison to the measured blood velocities
80
Two ways to avoid aliasing
raise PRF (nyquist limit), reduce doppler shift
81
Color doppler reports/measures
average or mean velocities
82
Color doppler is angle
dependent
83
If the angle between the sound beam and blood flow is 90 degrees
no doppler shift is created or measured, no color will appear in the vessel
84
To correct aliasing on color doppler is to
increase scale/PRF/nyquist limit
85
Increasing the color doppler scale
decreases the sensitivity to low velocity flow
86
Identifies only the presence of a doppler shift
power doppler
87
Power doppler does not evaluate
velocity or direction
88
Power doppler mode is
non-directional color doppler
89
Advantages of power doppler mode
increases sensitivity to low flow/low velocity flow, unaffected by doppler angles, no aliasing
90
Disadvantages/limitations of power doppler mode
no velocity or flow direction, low frame rate
91
Appears as a hyperechoic region beneath tissue with abnormally LOW attenuation
enhancement
92
Enhancement is completely unrelated to
speed of sound in soft tissue
93
What assumption is not true with enhancement
#6 the strength of a reflection is related to the characteristics of the tissue creating the reflection
94
Appears when the sound energy is transmitted in a direction other than along the beams main axis
lobes
95
Lobe artifacts degrade
lateral resolution
96
What assumption is not true with lobes
#4 reflections arise from structures located along the beams main axis
97
Lobe artifact and true reflector are located ______ and ______
side by side, at the same depth
98
Created when sound reflects off a strong reflector and is redirected toward a second structure
mirror image
99
Mirror artifact is located
deeper than the real structure
100
Slice thickness artifact is related to dimension of the beam that is
perpendicular to the imaging plane
101
Small amplitude echoes and results from many sources
noise
102
Noise is more likely to affect ______ regions rather than ______
low level hypoechoic regions, bright echogenic areas
103
Phantoms are an
objective standard
104
Have ultrasonic features similar to soft tissue, used to evaluate gray scale, tissue texture, multi focus
tissue equivalent phantom
105
Tissue equivalent phantom is similar to soft tissue in what 4 ways
speed of sound in phantom is 1540 m/sec, attenuation, scattering characteristics, echogenicity
106
Region close to the transducer where images are inaccurate
dead zone
107
In dead zone, it extends from the transducer to
shallowest depth where reflection appears
108
Dead zone is assessed with the
shallowest pins in a test phantom
109
What can be used for help with dead zone for superficial structures
acoustic standoff (or gel pad)
110
Minimum distance at which two side by side pinds are displayed as two distinct images, PERPENDICULAR TO SOUND BEAM
lateral resolution
111
Smallest distance at which two pins positioned PARALLEL to the sound beam are displayed as two distinct echos
axial resolution
112
Quality of being worthy, honored or esteemed
dignity
113
Factors that make a patient vulnerable to a loss of dignity include
advanced age, infirmity, lack of privacy
114
A primary mandate regarding clinical ultrasound is that the
benefit to the patient must outweigh the risk of the exam
115
Maximal heating is related to the beams
SPTA intensity
116
Interaction of sound waves with microscopic, stabalized, gas bubbles (gaseous nuclei) in the tissues
cavitation
117
Proposed that bioeffects result from tissue temperature elevation
thermal mechanism
118
It is ______ to use diagnostic ultrasound in a non-medical setting for entertainment
inappropriate
