Chapter 1 penny Flashcards
1
Q
the conversion of sound energy to heat
A
absorption
2
Q
the interference pattern caused by scatterers that produces the granular appearances of tissue on a sonographic image
A
acoustic speckle
3
Q
changes that occur within a medium as a result of sound traveling through that medium
A
acoustic variables
4
Q
the maximum or minimum deviation of an acoustic variable from the average value of that variable; the strength of the reflector
A
amplitude
5
Q
a decrease in the amplitude and intensity of the sound beam as sound travels through tissue
A
attenuation
6
Q
the rate at which sound is attenuated per unit depth
A
attenuation coefficient
7
Q
the ability to accurately identify reflectors that are arranged parallel to the ultrasound beam
A
axial resolution
8
Q
scattered sound waves that make their way back to the transducer and produce an image of the display
A
backscatter
9
Q
the ratio of the center intensity to the average spatial intensity; also referred to as the SP/SA factor or beam uniformity coefficient
A
beam uniformity ratio
10
Q
technology used to create comparable transducer technology to piezoelectric materials
A
CMUT
11
Q
an area in the sound wave of high pressure and density
A
compression
12
Q
sound that is continuously transmitted
A
continuous wave
13
Q
the process of reducing the number of cycles of each pulse in order to improve axial resolution
A
damping
14
Q
a unit that establishes a relationship or comparison between two values of power, intensity, or amplitude
A
decibels
15
Q
mass per unit volume
A
density
16
Q
relationship that implies that if one variable decreases, the other decreases or if one variable increases the other increases
A
directly related
17
Q
how far apart objects are; may also be referred to as vibration or displacement
A
distance
18
Q
the percentage of time that sound is actually being produced
A
duty factor
19
Q
elasticity
A
stiffness
20
Q
the number of cycles per second
A
frequency
21
Q
the depth at which sound has lost half of its intensity
A
half-intensity depth
22
Q
half intensity depth
A
half value layer thickness
23
Q
a unit of frequency
A
hertz
24
Q
a device used to measure the output intensity of the transducer
A
hydrophone
25
the resistance to the propagation of sound through a medium
impedance
26
Newton's principle that states that an object at rest stays at rest and an object in motion stays in motion unless acted on by an outside force
inertia
27
the power of the wave divided by the area over which it is spread; the energy per unit area
intensity
28
the percentage of sound reflected at an interface
intensity reflection coefficient
29
the percentage of sound transmitted at an interface
intensity transmission coefficient
30
the dividing line between two different media
interface
31
relationship that implies that if one variable decreases, the other one increases, and vice versa
inversely related
32
waves in which the molecules of the medium vibrate back and forth in the same direction that the waves are traveling
longitudinal waves
33
any form of matter
medium
34
reflectors that are smaller than the wavelength of the incident beam
nonspecular reflectors
35
angle of incidence is 90 degrees to the interface
normal incidence
36
angle of incidence is less than or greater than 90 degrees to the interface
oblique incidence
37
a measurable quantity
parameter
38
the movement of molecules due to propagating sound energy
particle motion
39
distance to the reflector
path length
40
the time is takes for one cycle to occur
period
41
a material that generates electricity when pressure is applied to it, and one that changes shape when electricity is applied to it; also referred to as the element or crystal
piezoelectric materials
42
the rate at which work is performed or energy is transmitted
power
43
force per unit area of the concentration of force
pressure
44
to transmit through a medium
propogate
45
the speed at which a sound wave travels through a medium
propagation speed
46
the time during which the sound is actually being transmitted; the "on" time
pulse duration
47
the number of pulses of sound produced in 1 second
pulse repetition frequency
48
the time taken for one pulse to occur
pulse repetition period
49
sound that is sent out in pulses
pulsed wave
50
an area in the sound wave of low pressure and density
rarefaction
51
the fixed quantity owed as the sound beam travels through tissue
rate
52
small scattering reflectors
Rayleigh Scatterers
53
the echo; the portion of sound that returns from an interface
reflection
54
the change in the direction of the transmitted sound beam that occurs with oblique incidence angles and dissimilar propagation speeds
refraction
55
the phenomenon that occers when sound waves are dispersed into different directions because of the small reflector size compared with the incident wavelength
scattering
56
law used to describe the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media
snell's law
57
a traveling variation in pressure
sound
58
the length of a pulse
spatial pulse length
59
reflections that occur when the sound impinges upon a large, smooth reflector at a 90 degree angle
specular reflections
60
the ability of an object to resist compression and relates to the hardness of a medium
stiffness
61
the total amount of sound in dB that has been attenuated at a given depth
total attenuation
62
type of wave in which the molecules in a medium vibrate at 90 degree to the direction of travel
transverse waves
63
sound waves of frequences exceeding the range of human hearing
ultrasound
64
the length of a single cycle of sound
wavelength
65
infrasound range
less than 20 Hz
66
audible sound range
20-20,000 Hz
67
ultrasound range
20,000 Hz or more
68
diagnostic ultrasound range
between 2 and 15 MHz (or higher)
69
pressure units
Pascals or pounds per square inch
70
density units
kg/cm3
71
particle motion units
feet, inches, centimeters, or miles
72
period units
us
73
frequency units
Hz, kHz, MHz
74
if frequency increases, period _______
decreases
75
if frequency decreases, period ________
increases
76
Formula for period
T = 1 / f
77
formula for frequency
f = c / ^
78
if stiffness increases, propagation speed _______
increases
79
if density increases, propagation speed _______
decreases
80
formula for propagation speed
c = e / p
81
wavelength units
mm
82
if frequency increases, wavelength ______
decreases
83
if frequency decreases, wavelength _______
increases
84
formula for wavelength
^ = c / f
85
amplitude units
Pa
86
power units
W and mW
87
intensity units
W/cm2 mW/cm2
88
______ and ______ are proportional to amplitude squared
power
intensity
89
power decreases as amplitude _______
decreases
90
intensity is proportional to
power
91
formula for intensity
I = Power / Area
92
formula for impedance
z = pc
93
pulse repetition frequency units
kHz
94
if imaging depth increases PRF
decreases
95
if imaging depth decrease PRF
increases
96
PRP units
ms
97
If PRF decreases PRP
increases
98
If PRF increases PRP
decreases
99
Pulse duration units
us
100
formula for pulse duration
PD = nT
101
Duty factor units
no units
102
duty factor formula
df = pd / prp
103
SPL unit
mm
104
SPL formula
SPL = n^
105
increasing frequency = ________ attenuation
increasing
106
increasing path length = _______ attenuation
increasing
107
formula for total attenuation
TA = f / 2 x L
108
smooth surface
border is larger than incident wavelength
angle dependenct
specular reflectors
109
rough surface
border is smaller than incident wavelength
not angle dependent
nonspecular reflectors
110
Formula for ITC
ITC = 1 - IRC
111
Formula for IRC
IRC = Ir / Ii = [z2 - z1 / z2 + z1]2
112
Normal perpendicular incidence
impedance mismatch
percentage or intensity of sound reflected and transmited at an interface
reflection
113
oblique incidence
propagation speed mismatch
angle of transmitted sound
refraction
114
snells law formula
sin 0t = sin 0i (c2 / c1)
115
formula for BUR
BUR = SP/SA
116
Temporal average formula
TA = PA x DF
117
list intensities from lowest to highest
SATA, SPTA, SAPA, SPPA, SATP, SPTP
118
3 primary acoustic variables
pressure, density, particle motion
119
two parts of a cycle
compression rarefaction
120
particle motion units
mm
121
parameters of sound waves
period
frequency
amplitude
power
intensity
propagation speed
wavelength
122
average speed of sound in soft tissues
1540 m/s or 1.54 mm / us
123
Propagation speed is influenced by _____ and ______.
density stiffness
124
if frequency increases, wavelength _____
decreases
125
the faster the propagation speed, the _____ the wavelength
longer
126
wavelength formula
^ = c / f
127
amplitude doubles, power ______
quadruples
128
amplitude triples, power increases _____
9 times
129
amplitude halved, power reduced by _____
one-fourth
130
impedance units
rayls
131
large impedance = ______ reflection
stronger
132
more subtle impedance difference = _____ reflection
weaker
133
impedance the same = _____ reflection
no
134
Parameters of pulsed wave ultrasound
PRP
PRF
PD
DF
SPL
135
typical values of PRF
between 1,000 and 10,000 Hz
136
duty factor formula
DF = PD / PRP
137
reduces the long "ring" of a vibrating crystal to 2 or 3 cycles per pulse
damping
138
Spatial pulse length depends on _____ and _____.
wavelength and number of cycles in each pulse
139
shorter wavelengths result in ____ SPLs
shorter
140
device that is creating the sound
sound source
141
tissue through which sound waves are traveling
medium
142
3 mechanisms of attenuation
absorption reflection scattering
143
greatest contributor to attenuation
absorption
144
used when evaluating two intensities, powers, or amplitudes
dBs
145
if an intensity or power has doubled, it has changed by __ dB
3
146
if an intensity of power halves, it has changed by __dB
-3
147
as path length increases, attenuation ____
increases
148
average rate of attenuation in soft tissue
.7 dB/cm/MHz
149
In soft tissue the HID is equal to _____
6/f
150
higher frequency transducers = _____ intensity of scatter
higher
151
reflection formed when two criteria are met:
normal incidence
two media have different impedances
152
two types of oblique incidence
obtuse
acute
153
Intensity of sound reflected at an interface depends on:
intensity of transmitted sound
difference in impedances between two media
154
the average intensity across the face of the entire beam
spatial average
155
highest of all temporal intensities
temporal peak
156
the average of all the intensities during both transmission and the listening period
temporal average
157
lowest of all temporal intesnsities
TA
158
measured only during pulse transmission
PA
159
TA formula
TA = PA x DF
160
lowest of the intensities
SATA
161
highest of the intensities
SPTP
162
The _____ is altered by adjusting the depth control on the machine
PRF
163
In increase in PRF a _________ in DF
increase
164
As imaging depth increases prf
decreases
165
the amount of refraction that occurs at an interface
snells law
166
pressure is typically expressed in
pascals
167
the attenuation coefficient in soft tissue is equal to
one-half of the operating frequency
168
requires an oblique interface and a propagation speed mismatch
refraction
169
density is typically measured in
kilograms per cm cubed
170
what is the total amount of attenuation that occurs if a 6 MHz sound beam travels through 4 cm of tissue
12 dB
171
as imaging depth increases PRP
increases
172
What are the units of DF?
unitless
173
density and propagation speed are ____ related
inversely
174
the inertia of the medium describes its
density
175
if the angle of incidence is 40 degrees, what is the angle of transmission at the interface if medium 1 has a propagation speed of 1320 m/s and medium 2 has a propagation speed of 1700 m/s?
<40 degrees
176
In clinical imaging, the wavelength typically mesaures between
0.1 and 0.8 mm
177
whatr is the change in intensity if the power decreases by half?
intesnity is halved
178
Damping of the sound beam _____ the SPL
reduces
179
adding damping to the transducer improves which type of resolution?
axial
180
what is the change in power if amplitude triples?
it increaes nine times
181
The portion of the sound beam where teh molecules are farther apart describes an area of
rarefaction
182
if only the density of a medium is increased, then the
propagation speed will decrease
