Physics Final Fall 2015 Flashcards
(111 cards)
1
Q
Descriptive words Macro means _____ and Micro means _____.
A
Bigger; Smaller
2
Q
The symbol for millions is _____ and millionths is _____.
A
Mega (M) ; Micro (u)
p.6
3
Q
The symbol for hundreds is _____ and the symbol for hundredths is _____.
A
Hecto (h) ; Centi (c)
p.6
4
Q
A wave with a frequency of 15,000 MHz is _____.
A
ultrasonic
p.22
5
Q
If the power of a wave is halved, the intensity is reduced to one-fourth its original value.
A
False; if we halve power, intensity is also halved
p.43
6
Q
If the amplitude of a wave is increased to 3 times its original value, the intensity is increased by 6 times.
A
False; intensity increases by 9 times
p.41
7
Q
Propagation speed is determined by the medium.
A
True; only determined by medium
p.36
8
Q
Propagation speed increases as frequency increases.
A
False; speed and frequency are unrelated
p.43
9
Q
We need one intensity to calculate decibels.
A
False; two intensities
p.77
10
Q
As the path length increases, attenuation of US in soft tissue increases.
A
True
p.89
11
Q
Spatial peak intensity is always lower than the spatial average intensity.
A
False; spatial peak is higher than spatial average
p.70
12
Q
In addition to location within the beam, sound wave intensities also vary over time.
A
True; intensities are reported in various ways with respect to time and space
p.74
13
Q
SPTA intensity is the most relevant intensity with respect to tissue heating.
A
True
p.74
14
Q
The duty factor is a unit less number with a value between 0 and 1.
A
True
p.74
15
Q
There are two different methods to measure and report intensities.
A
False; 6 measurements
p.73
16
Q
The duty factor for a pulsed ultrasound system is 2%.
A
False; 0.2%
p.61
17
Q
An ultrasound beam has the same intensity at different depths or at different side to side locations within the beam.
A
False; the beam does not have the same intensity at different depths
p.70
18
Q
At a particular depth, the center of a sound beam is more intense than the edges.
A
True
p.70
19
Q
Temporal peak intensity is maximum in time.
A
True
p.71
20
Q
How many hertz is 3MHz?
A
3,000,000
p.9
21
Q
How much bigger is a billion than a million?
A
1000 times
p.10
22
Q
What are the units of wavelength?
A
mm (units of length)
p.33
23
Q
What are the units of frequency?
A
Hz
p.21
24
Q
What are the units of intensity?
A
W/cm squared
p.31
25
What are the units of propagation speed?
m/s (distance/time)
| p.36
26
What are the units of period?
microseconds (time)
| p.20
27
Of the following which grouping is determined by the sound source?
```
period
frequency
amplitude
power
intensity
wavelength (both sound and medium)
p.40
```
```
Pulse duration
PRP
PRF
Duty Factor
Pg 63
```
28
If the intensity remains the same while the power is doubled, what happens to the beam area?
double
| p.44
29
A sound beam travels a total of 10cm in 2 seconds. What is the speed of the sound in this medium?
5cm/sec
| p.44
30
What term describes the time from the start of a pulse to the end of that pulse?
pulse duration
| p.65
31
Pulse Repetition frequency is the reciprocal of:
PRP
| p.58
32
db is a mathematical representation with a _____ scale.
logartithmic
| p.75
33
Rayleigh scattering is related to______.
frequency to the fourth power
| p.83
34
Which of these media have the greatest attenuation and the slowest speed?
air
| p.37 & 86
35
Which of the following mathematically describes the physics of refraction?
Snell's Law
sin (transmission angle)/ sin (incident angle) =
speed of medium 2/speed of medium 1
p.102
36
Two piezoelectric crystals are made from the same material. The thicker crystal will make a pulsed
transducer with ______?
lower frequency
| p.127
37
All of the following correctly describe an imaging transducer except:
```
(these are true)
low sensitivity
low Q
wide bandwidth
damped
p.121
```
38
When PZT’s temperature exceeds the Curie point, the PZT is _______?
depolarized
| p.121
39
PZT in an ultrasound transducer is also known as all the following:
```
ceramic
active element
crystal
lead zirconate titanate
ferroelectric
p.113
```
40
Which of the following describes the transducer component that reduces the “ringing” of the pulse?
```
backing material (damping element)
p.115
```
41
Mathematically, the Q factor is the main frequency divided by _____?
bandwidth
| p.119
42
Imaging transducers can also be referred to as ______?
pulsed wave transducer
| p.123
43
Which of the following crystals will produce sound with the lowest frequency?
thicker PZT crystals
PZT with lower speeds
p.125
44
The damping material in the transducer improves the system’s _____ resolution?
longitudinal
| p.126
45
If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6 MHz, then the
operating frequency of the transducer is ____MHz.
Frequency is not determined by the electrical signal
| p.126
46
The impedance of a transducer active element is 1,900,000 Rayls, and the impedance of the skin is 1,400,000 Rayls. What is an acceptable impedance of the matching layer?
between the active element and skin (1,726,000 rayls)
| p.127
47
Of the following, which transducer component is a thin barrier of cork or rubber that isolates or “uncouples” the internal components of the transducer from the case?
acoustic insulator
| p.115
48
In an imaging transducer, what is the purpose of attaching the backing material to the PZT?
Reduces the ringing of the PZT
p.115
49
Which of the following probes creates a beam with the deepest focus?
large diameter PZT
high frequency
p.136
50
Frequency and near zone length are related in what way?
directly related
| p.138
51
Which of the following probes creates a beam with the least divergence?
large diameter, high frequency (6 mm diameter, 8 MHz)
| p.141
52
Which of the following probes creates a beam with more divergence?
small diameter, low frequency
| p.141
53
Which of the following determines the frequency of sound created by a pulsed wave transducer?
speed of sound in the PZT
thickness of the PZT
p.123
54
Which of the following determine the spread of a sound beam in the far field?
transducer diameter
frequency of the sound
p.139
55
```
Of the following which term does not belong with the others?
Possible multiple choice question...
A. Focus
B. End of the near zone
C. End of the Fraunhofer zone
D. Middle of focal zone
```
End of Fraunhofer zone because it is the end of the sound beam; the others are related to focus
p.134
56
The frequency of a transducer does not change. If the diameter of the new piezoelectric increases, what
happens to the wavelength?
No change
| p.143
57
Imaging to a greater depth of view requires _____ listening?
more
| p.55
58
When reporting a beam’s intensity at the location where it is maximum is referred to as?
spatial peak intensity
| p.70
59
The highest temporal intensity is which of the following?
```
temporal peak (I tp)
p.72
```
60
Choose the units for reporting intensity from the following:
watts/cm^2
| p.74
61
Of the following which has the lowest value?
| Possible question... Intensity with lowest value?
SATA
| p.74
62
Which of the following is measured where intensity is maximum and averaged over all time?
SPTA
| p.73
63
Which intensity is measured over the entire cross-sectional area of the sound beam, and over all time?
SATA
| p.73
64
Which of the following mean the same as normal incidence?
```
perpendicular
orthogonal
right angle
ninety degrees
p.91
```
65
The intensity of the sound wave at the instant prior to striking a boundary is referred to as?
incident intensity
| p.92
66
The portion of the incident intensity that, after striking a boundary, continues on in the same general
direction that it was originally traveling is referred to as the?
transmitted intensity
| p.92
67
The percentage of the US intensity that is allowed to pass through when the beam reaches a boundary between two media is referred to as?
Intensity transmission coefficient (ITC)
| p.93
68
A sound wave with an intensity of 50W/cm2 strikes a boundary and is totally reflected. What is the intensity reflection coefficient?
100%
| p.94
69
The intensity reflection coefficient of sound is 99.9%. What percent of sound is transmitted into the body?
0. 1%
| p. 93
70
Specular reflections arise when the interface is ______?
smooth
| p.81
71
What do we know about oblique incidence?
Nothing
| p.104
72
Transmission with a bend is referred to as?
Refraction
| p.101
73
Snell’s law describes what physics?
quantifies the physics of refraction
| p.102
74
Sound wave strikes a boundary at normal incidence. The impedances of the two media are identical.
What percentage of the sound wave is refracted?
0%; refraction cannot occur with normal incidence
| p.105
75
Which of these media have the greatest attenuation and the slowest speed?
Air
Lung
p.37 & 86
76
What processes occur as the ultrasound passes through all media?
attenuation (reflection, scattering, absorption)
| p.81
77
Two waves are traveling through a medium and arrive at a location at the same time. What event takes
place?
interference
| pg 14
78
The percentage of time that a system is transmitting a pulse refers to which of the following?
Duty Factor
| p. 60
79
A 3MHz sound beam travels through two media. It attenuates 5 dB in medium A and 6 dB in medium B.
What is the total attenuation that the sound beam undergoes as it travels through both media?
11dB as sound travels attenuation simply adds up.
80
Which of these are considered the dominant contributor to attenuation?
absorption
| p.84
81
Attenuation in soft tissue is less than which of the following?
Muscle
Bone and lung
Air
p.86
82
Impedance is a characteristic of:
the medium only
| p.88
83
Which of these media have the greatest attenuation and the fastest speed?
Bone
| p.37 & 86
84
Hertz is a unit of measurement used to describe what wave characteristic?
Frequency
| p.24
85
A low frequency transducer is best at imaging which anatomical structure?
Deep organs
86
The percentage of the US intensity that is allowed to pass through when the beam reaches a boundary
between two media is?
intensity transmission coefficient
| pg. 93
87
Which of the following is the best estimate for attenuation coefficient of sound traveling in soft tissue?
one-half the frequency
0. 5dB/cm/MHz
p. 85
88
Attenuation is determined by two factors:
path length
frequency of sound
p.80
89
With longer distances and higher frequencies you have?
more attenuation
| p.80
90
With shorter distances and lower frequencies you have?
less attenuation
| p.80
91
Because attenuation means a weakening or a decrease, the dbs must be?
negative
92
Which term best describes redirection of sound in many directions?
scattering
| p.82
93
Reflections from a smooth reflector are referred to as?
specular
| p.81
94
When a boundary is rough, reflected sound is disorganized and random, also called?
diffuse reflection
backscatter
p.82
95
Rayleigh scattering increases dramatically with increasing frequency, which is the relation?
Rayleigh scattering = frequency to the fourth
| p.83
96
Acoustic Impedance is equal to?
density (kg/m^3) x prop speed (m/s)
| p.88
97
A sound wave is created by the transducer, reflects off of an object and returns to the transducer. The
depth of the reflector is 10 cm. The round trip time is 2 seconds. What is the speed of sound in the medium?
```
speed=distance/time
20 cm (there and back)/2 sec = 10 cm/sec
```
98
The time needed for a pulse to travel to and from the transducer and the reflector is called?
time of flight
| pg. 107
99
A sound wave is created by the transducer, reflects off an object and returns to the transducer in 52 microseconds.. How deep is the object and what is the total distance traveled?
4 cm; 8 cm
| p 108
100
The maximum imaging depth during an ultrasound exam is 5 cm. The sonographer adjusts the depth to
10cm. What happens to pulse repetition frequency?
PRF is halved; PRF is inversely related to depth
| p.112
101
The maximum imaging depth during an ultrasound exam is 4 cm. The sonographer adjusts the imaging depth to 8 cm. What happens to the pulse repetition period?
PRP is doubled; PRP is directly related to depth
| p.112
102
A sound wave is created by the transducer, reflects off an object, and returns to the transducer. The time of flight is 130 microseconds. What is the maximum PRF?
7,700 Hz
| p.112
103
A sound wave is created by the transducer, reflects off an object, and returns to the transducer. The go return time is 39 microseconds. What is the total distance traveled?
6 cm
| p.108
104
Axial resolution deals with structures that are ______ to the sound beam.
parallel
| p.145
105
As frequency increases, the numerical value of LARRD resolution _______?
is lower
| p.147
106
Which of the following has the highest axial resolution?
Less ringing (fewer cycles/pulse)
Higher frequency
p.147 & 150
107
Superior axial resolution is associated with the following?
Less ringing (fewer cycles per pulse)
Higher frequency
p.147
108
Two different transducers create pulses. Both transducers create sound with a frequency of 5MHZ.
Which of the following is more likely to create a better image in regards to axial resolution?
Transducer with lowest # cycles/pulse
| p.148
109
Which of the following transducers will create the lowest numerical value of axial resolution?
```
Shorter pulse duration
Shorter spatial pulse length
Less ringing (less cycles/pulse)
High frequency
p.148
```
110
Effects of focusing
```
Beam diameter in near field and focal zone are reduced
Focal depth is shallower
Beam diameter in far zone increases
Focal zone is smaller
pg. 156
```
111
Display modes
```
A-mode: amplitude
x-axis = depth y-axis = amplitude
B-mode: brightness
x-axis = depth z-axis = amplitude
M-mode: motion
x-axis = time y-axis = depth
```
