Davies Quizlet Starred Flashcards
1
Q
A hydrophone measures (2)
A
Duty factor
Pressure amplitude
2
Q
PHI stands for
A
Protected health information
3
Q
What does mechanical index indicate on ultrasound system
A
Liklihood of cavitation during an US exam
4
Q
Potential bio effect occuring through absorption of sound energy by tissue
A
Heating
5
Q
You notice TI is greater than 1. Any increase in temp would most likely be greatest in
A
Bone
6
Q
Motion of particles in a fluid is sometimes observed in an intense US beam. This is termed
A
Acoustic streaming
7
Q
TI reading is 1. What does this indicate?
A
The output level is high enough that temperature could increase as much as 1 C if the transducer were held stationary
8
Q
When scanning with pulsed-wave dop, you would affect the acoustic exposure by changing which of the following?
A
PRF
9
Q
Tissue with the highest rate of attenuation
A
Lung
10
Q
Propagation speed is lowest in which tissue
A
Fat
11
Q
Purpose of gel coupling medium
A
Decrease impedance mismatch
Sound does not travel through air
12
Q
While imaging a cyst, you notice shadowing posterior to each lateral border of the cyst. What is the source of the shadows?
A
Bending of the sound beam due to different media propagation speeds
13
Q
Diffraction
A
Pattern produced by a sound beam after passing through a small aperture
14
Q
Sound propagates faster in materials with greater
A
Stiffness
15
Q
During an US, you would most likely encounter refraction in this fiew
A
Curved interface
16
Q
Relationship to frequency and absorption
A
If frequency is doubled, absorption is doubled
17
Q
While performing a sonogram, you encounter the following interfaces*** which will produce the weakest REFLECTED signal
A
Organ parenchyma/organ parenchyma
18
Q
You are scanning a large mass that is composed primarily of fat. What is most likely to happen?
A
Axial misrepretation of objects distal to the mass on the screen due to the slower propagation speed through fat
19
Q
When you change the transmit frequency, what is altered?
A
Number of cycles per second
20
Q
When the sound beam is refracted, what may you detect on the ultrasound image?
A
lateral misregistration
21
Q
What interaction of ultrasound and tissue is primarily responsible for imaging the internal structure of organs?
A
scattering
22
Q
when you image a specular reflector, the strength of the recieved signal depends on (2)
A
- angle of incidence
- difference in acoustic impedance
23
Q
T/F frequency, intensity, amplitude and wavelength change as the beam propagates through tissue
A
true
24
Q
axial resolution is determined chiefly by
A
pulse duration
25
benefits of harmonic imaging (2)
- improve lateral resolution
| - decrease grating lobes
26
what increases SPL?
n = number of cycles per pulse
27
increased bandwith improves what type of resolution
axial
28
For a linear array transducer consisting of a single row of elements, what method is most used to focus the beam in the elevational direction?
mechanical focusing
29
downfall to small footprint transducer
degrades resolution
30
sector display format that narrows to a point at the transducer surface. what transducer?
phased array
31
type of transduer that has the same measurement for elevational and lateral resolution
annular array
32
During the course of a sonographic exam, you notice lateral splaying of the echoes in the far field. What can you do to improve the image?
Increase the number of transmit focal zones and optimizes their location
33
You suspect that a bright spot on the B-mode image is a calcification, but a posterior acoustic shadow is not present. How can you best optimize your system to demonstrate a shadow distal to the calcification
Increase the transducer frequency
34
What is the purpose of the radiofrequency shield that is placed around the crystal and backing material of the ultrasound probe?
It reduces electromagnetic interference
35
What is the optimal thickness for the matching layer?
One-fourth of a wavelength
36
Parallel processing, define
A method used to improve frame rates with multizone electronic focusing is termed:
37
Which of the following best describes the f-number?
Focal length divided by the aperture
38
If you wish to perform a sonogram with the largest possible field of view in both the near field and at depth, what type of array transducer would be most preferable?
Curved array
39
how many cycles in a pulse with B-mode
1-3
40
What is purpose of applying multiple matching layers to the transducer face? (2)
- decreases impedance
| - increased bandwidth
41
What is the main advantage the stand-off pad provides to improve the image?
The stand-off pad increases the distance between the transducer and the mass, making it more likely that the mass will be located close to the elevational focus of
42
If you are using a transducer with poor elevation resolution, which of the following problems are you most likely to encounter?
Inability to clearly demonstrate small cystic structures
43
What can you do to improve contrast resolution in the ultrasound image?
Use a 2D or matrix array transducer
44
Which represents the best measure of resolution for modern day ultrasound scanners?
Axial
45
Which of the following transducer types is best suited to cardiac imaging?
Phased array
46
tissue equivalent phantom measures (4)
- axial resolution
- contrast resolutino
- lateral resolution
- slice thickness
47
You notice a loss of detail in the lateral dimension of the ultrasound image. What can you do to improve this?
increase scan line density
48
What is the purpose of curving the transducer elements or applying a lens over the elements?
To provide focusing in the out-of-plane (elevational) direction
49
What disadvantage and advantage is related to the use of a tightly curved array transducer?
advantage: field of view is improved
disadvantage: Lateral resolution degrades with depth
50
In order to focus a sound beam relatively far away from the transducer, it is advantageous to:
Increase the diameter of the element
51
increasing frame averaging aka persistence does what to frame rate
decreases
52
The technique of frame averaging during real-time acquisition is designed to
Reduce random noise
53
You are performing a sonographic examination and select the tissue harmonics operating mode. What advantage will you obtain over conventional imaging?
Improved contrast resolution
54
What is a typical frame rate for B/mode real-time imaging?
10-50 Hz
55
The term duty factor is defined as
The fraction of time the transducer is actively transmitting sound
56
If you increase the pulse repetition frequency and leave all other controls unchanged, what will happen?
frame rate decreases
57
What effect will you see in image if you increase the reject level?
Decreased low-level echoes
58
If sound did not attenuate with increasing depth, what system control would you no longer need?
reject
59
What system component determines the repetition frequency?
pulser
60
What is the purpose of the preamplification of the incoming signal that occurs in the transducer assembly?
To increase echo voltages before noise is induced through the cable
61
What function of the receiver converts electrical signals from radiofrequency to video form?
demodulation
62
Which of the following best describes M-mode?
Depth of reflectors along a single line of sight vs time
63
What information is present in the M-mode display? (3)
time, motion pattern, amplitude
64
A digital scan converter is another name for what system component?
image memory
65
Where are images stored in the ultrasound system?
scan converter
66
The picture elements in a scan converter matrix are termed
pixels
67
Digital to analog conversion of the ultrasound signal must occur at what part of the imaging process?
between the scan converter and the display
68
when you "freeze' the image, where is the echo information stored?
scan converter
69
What is the order in which the signal travels in the ultrasound system?
Transducer, receiver, scan converter, display
70
Of the following, which is the best choice to help you demonstrate tissue boundaries that are not perpendicular to the sound beam?
spatial compounding
71
benefits of 3D imaging over 2D (2)
- ability to display image planes impossible to obtain with 2D imaging
- Ability to display orthogonal planes simultaneously
72
You may observe a mirror image artifact with which imaging mode?
ALL OF THEM - b-mode, spectral, colour, power
73
Which imaging technique may increase visualization of the reflections from blood flow on the real-time ultrasound image?
harmonics
74
Which of the following artifacts commonly results in echoes filling in the lumen of small vessels?
partial volume
75
Propagation speed error results in which sonographic appearance?
Improper axial position of an echo
76
When you select harmonic imaging, which artifact is less likely to be observed?
Grating lobes
77
When you select compound imaging, which artifact is less likely to be observed? (4)
- refraction
- -shadowing
- enhancement
- speckle
78
what will decrease acoustic speckle in your image (2)
- frame averaging
| - compound
79
If you wish to improve border definition, what imaging enhancement should you use?
spatial compounding
80
What can you do to improve visualization of distal acoustic shadowing from calcification?
harmonics
81
What helps to improve the axial resolution in a B-mode image?
increased bandwidth
82
what helps to improve the lateral resolution in a B-mode image?
increased aperture
83
what helps to improve the elevation resolution in a B-mode image?
Focusing with an acoustic lens
84
What technique would be most likely to produce grating lobes in your image?
beam steering
85
What term is used to describe a 3-dimensional pixel element in 3D sonography?
voxel
86
What 2D limitation is addressed by 3D ultrasound imaging?
3D provides visibility of the coronal plane
87
The packet size in color Doppler refers to the number of
Pulse/listen cycles per acoustic scan line
88
A commonly used process for determining direction in a Doppler instrument is
Phase quadrature detection
89
What method is used to steer the color beam with a linear array transducer?
What method is used to steer the color beam with a linear array transducer?
90
What would be the most likely result from increasing the transmit frequency of the color Doppler?
Improved sensitivity to slow flow
91
During Doppler interrogation of the carotid artery, you detect mirroring. Which of the following is a common cause of this artifact?
Doppler angle of interrogation near 90
92
The rapid technique used in most color Doppler systems to obtain the mean doppler frequency shift is:
Autocorrelation
93
packet size
number of pulses per scan line
94
Color flash artifact obscuring the anatomy of interest in an exam of the abdominal aorta. What can you do to reduce impact of the flash?
Increase the wall filter
95
You have increased the packet size while using color Doppler to evaluate flow. What position result will occur from this action?
Improved signal-to-noise ratio
96
What two controls affect the spatial resolution of the color image?
frequency and line density
97
Which condition is most likely to occur in patients having a normal arterial waveform shape, but low velocities across all vessels?
Low cardiac output
98
Atherosclerosis begins within:
the intima
99
String test objects are used to evaluate:
Doppler accuracy
100
recommended ingredient in cleansers for intracavitary probes?
Glutaraldehyde
101
You are using a transducer with poor elevation resolution. What problem will most likely be encountered as a result?
You will not be able to clear anechoic tubes oriented with their axis in the scan plane
102
When measuring penetration on a tissue-mimicking phantom, how should the master gain and acoustic output be adjusted?
Maximum gain, maximum acoustic output
