Chapter 2 Kremkau Flashcards
1
Q
conversion of sound to heat
A
absorption
2
Q
derived from the Greek word for hearing
A
Acoustic
3
Q
pressure, density, and particle vibrations
A
acoustic variables
4
Q
indicators of the strength of sound, related to how loud the sound would be if it could be heard
A
amplitude
5
Q
the weakening of sound while it propagates
A
attenuation
6
Q
the attenuation that occurs with each centimeter the sound wave travels. Its units are decibels per centimeter. The farther the sound travels the greater the attenuation
A
attenuation co-efficient
7
Q
decibels per centimeter
A
attenuation
8
Q
sound scattered back in the direction from which it originally came
A
backscatter
9
Q
range of frequencies
A
bandwith
10
Q
the shorter the pulse, the _____ the bandwidth
A
broader
11
Q
regions of high pressure and density
A
compression
12
Q
echoes that arrive at transducer in such a way that they reinforce each other
A
constructive interference
13
Q
ultrasound in which cycles repeat indefinitely
A
continuous wave
14
Q
liquid suspensions that are injected into the circulation intravenously are used to increase echogenicity
A
contrast agents
15
Q
a gel that is used to provide a good sound path from the transducer
A
coupling medium
16
Q
pressure and density increase and decrease, and particles of the medium oscillate in motion
A
cycle
17
Q
units used to quantify attenuation
A
decibel
18
Q
the concentration of matter
(mass per unit volume)
A
density
19
Q
echoes that may arrive at the transducer in such a way that they partially or totally cancel each other out
A
destructive interference
20
Q
the fraction of time that pulsed ultrasound is on. Indicates how much of the time the ultrasound is on
A
duty factor
21
Q
the reflected and scattered sound waves
A
echo
22
Q
the ability to accomplish work
A
energy
23
Q
bandwidth divided by operating frequency. Unitless. Describes how large the bandwidth is compared with operating frequency
A
fractional bandwidth
24
Q
expresses the number of cycles in a wave that occur in 1 second
A
frequency
25
original frequency
fundamental frequency
26
any other wave shape containing additional frequencies that are even and odd multiples of the original frequency
harmonics
27
one cycle per second
hertz
28
determines how much of an incident sound wave is reflected back into the first medium and how much is transmitted into the second medium. Equal to the density of a medium multiplied by the propagation speed in it. Increases if density increases or if propagation speed increases
impedance
29
unit for impedance
Rayl
30
the direction of travel with respect to the boundary given
incidence angle
31
the rate at which energy passes through a unit area
intensity
32
dividing the reflected (echo) intensity by the incident intensity that is reflected
intensity reflection coefficient
33
dividing the transmitted intensity by the incident yields the fraction of the incident intensity that is transmitted into the second medium
intensity transmission coefficient
34
scatterers moving in and out of beam, interference alternates between being constructive and being destructive, resulting in a displayed dot pattern - a grainy appearance - that does not directly represent scatterers but, rather, represents the interference pattern of the scatterer distribution scanned
interference
35
1,000 Hz
Kilohertz
36
sound is a mechanical, compressional wave in which back and forth particle motion is parallel to direction of wave travel. Also know as compressional wave.
Longitudinal wave
37
a thing that sound propagates through
medium
38
1,000,000 Hz
Megahertz
39
propagation in which speed depends on pressure and the shape of the wave changes
nonlinear propagation
40
when the incident sound beam encounters the boundary between two mediums at an angle
oblique incidence
41
half-value depth for the specific ultrasound frequency
penetration
42
the time is takes for one cycle to occur
period
43
denotes a direction of travel of the ultrasound wave perpendicular to the boundary between the two media
perpendicular incidence
44
the rate at which energy is transferred from one part of a system to another or from one location to another. Energy transferred divided by the time required to transfer, that is, the transfer rate.
Power
45
Units of Power
Watts and MilliWatts
46
sound is a traveling variation in _______.
pressure
47
the speed at which a particular value of an acoustic variable moves, at which a cycle moves, and at which the entire wave moves
propagation
48
the speed with which a wave moves through a medium
propagation speed
49
ultrasound pulse is a few cycles of ultrasound. They are separated in time with gaps of no ultrasound
pulse
50
the time it takes for one pulse to occur. Equal to period times the number of cycles in the pulse. Expressed in microseconds
pulse duration
51
the number of pulses that occur in 1 second
pulse-repetition frequency
52
refers to the time from the beginning of one pulse to the beginning of the next. Its common units are milliseconds.
Pulse-repetition period
53
not on continuously. a few cycles of ultrasound
pulsed ultrasound
54
the distance to a reflector calculated from the propagation speed and pulse-round trip travel time
range equation
55
regions of low pressure and density
rarefaction
56
return of the sound wave back to the transducer
reflection
57
a change in acoustic impedance across a boundary between tissues
refraction
58
cellular tissues or particle suspensions such a blood
scatterer
59
the redirection of sound in many directions by rough surfaces (sometimes called diffuse scattering) or by heterogeneous media
scattering
60
transverse wave
shear wave
61
the length of a pulse from front to back. Equal to the length of each cycle times the number of cycles in the pulse
Spatial pulse length
62
a form of acoustic noise in sonographic imaging
speckle
63
a type of surface reflectance often described as a mirrorlike reflection of light from the surface
specular reflection
64
the resistance of a material to compression
stiffness
65
related to how loud the sound would be if it could be heard. Amplitude and intensity are indicators
strength
66
depends on propagation speeds in the media
transmission angle
67
shear wave
transverse wave
68
frequency higher than the range of human hearing
ultrasound
69
a traveling variation in one or more quantities called wave variables
wave
70
the length of space that one cycle takes up
wavelength
71
sound of a frequency too low for human hearing
infrasound
72
if frequency increases, period _______.
decreases
73
if frequency increases, wavelength _______.
decreases
74
Highest propagation speeds
solids
75
lowest propagation speeds
gases
76
average propagation speed in soft tissues
1.54 mm/us
77
If PRF increases, PRP ________.
decreases
78
Sonographic pulses are typically __-__ cycles long
2-3
79
Doppler pulses are typically __-__ cycles long
5-30
80
If frequency increases, pulse duration _______.
decreases
81
If the number of cycles in a pulse is decreased, pulse duration is _______.
decreases
82
If the pulse duration increases, the duty factor ______.
increases
83
If PRF increases, duty factor _______.
increases
84
if the number of cycles in a pulse increases, SPL ______.
increases
85
_______ pulses improve sonographic image detail resolution
shorter
86
if beam power increases, intensity ________.
increases
87
if attenuation coefficient increases, attenuation _______.
increases
88
if path length increases, attenuation _______.
increases
89
if frequency increases, attenuation ________.
increases
90
if frequency increases, penetration ________.
decreases
91
impedance increases if density of propagation speed ______.
increase
92
if the difference between the impedances increases, the ITC _______.
increases
93
if IRC increases, ITC _______.
decreases
94
while round trip time increases, calculated reflector distance _______.
increases
95
frequency
period
wavelength
propagation speed
amplitude
intensity
terms used to describe sound
96
when pressure is higher, the medium is ______.
denser
97
when pressure is lower, the medium is ________.
less dense
98
human hearing range
20-20,000 Hz
99
Infrasound range
less than 20 Hz
100
Ultrasound range
20,000 Hz or more
101
T = 1 / f
Period
102
also known as cycle length
wavelength
103
propagation speed units
m/s mm/us
104
wavelength depends on ______ and ____.
frequency
propagation speed
105
^ = c / f
wavelength
106
Shear wave propagation speeds in soft tissues
.5 - 10 m/s
107
rate of change of a position of an object
speed
108
speed with direction of motion specified
velocity
109
propagation speed depends on ______ and ______.
density
stiffness
110
c (m/s) = elasticity / density
propagation speed
111
increase in stiffness, _______ propagation speed
increases
112
increase in density ______ propagation speed
decreases
113
In nonlinear propagation, propagation speed depends on ______.
pressure
114
PRF units
kHz
115
PRP units
milliseconds
116
PRP decreases, PRF _______
increases
117
PD = n x T
pulse duration
118
PD decreases if number of cycles in pulse _______.
decreases
119
PD decreases if frequency _______.
increases
120
Duty factor continuous wave
100%
121
_______ pulses increases duty factor
longer
122
Higher PRFs _________ DF
increases DF
123
units of DF
no units
124
DF = PD (us) / PRP (us) = PD (us) x PRF (kHz) / 1000 kHz/MHz)
Duty Factor
125
Typical DFs for sonography
.1-1.0%
126
Typical DFs for Doppler ultrasound
.5-5%
127
SPL = ^ x n
Spatial pulse length
128
SPL increases with _______ and ________.
wavelenth
129
SPL increases with _______ and ________.
wavelength
number of cycles in the pulse
130
SPL decreases with ________ frequency.
increasing
131
units for spatial pulse length
mm
132
shorter pulse lengths ______ resolution
improve
133
the higher number of frequencies, the _______ the bandwidth
broader
134
determines the number of scan lines produced per second
frequency
135
operating frequency / bandwidth
quality factor
136
shorter pulses have broader bandwidth and ______ QFs.
lower
137
indicators of the strength of sound
amplitude and intensity
138
energy transferred divided by time required to transfer energy (transfer rate)
power
139
units for power
watts and milliwatts
140
beam area units
cm squared
141
intensity units
w/cm2 mw/cm2
142
power divided by amplitude
Intensity
143
increase in power ______ intensity
increases
144
increase in area _______ intensity
decreases
145
proportional to amplitude squared
intensity
146
if amplitude is doubled, intensity is ________.
quadrupled
147
if amplitude is halved, intensity is _______.
quartered
148
the greatest intensity found across the beam
spatial peak
149
the average for all values found near the center and the small values near the periphery
spatial average
150
the greatest intensity found in the pulses as it passes by
temporal peak
151
the average for all values found in a pulse include the large values found at its beginning and the smaller values found near the end
pulse average
152
includes the "dead" time between pulses where there is zero intensity
temporal average
153
TA = PA x DF
temporal average
154
reduction in amplitude and intensity as sound travels through
attenuation
155
dominant factor of attenuation
absorption
156
attenuation coefficient units
db/cm
157
corresponds to an intensity ratio of one-half, that is, an intensity reduction of 50%
3dB
158
corresponds to an intensity ratio of one-tenth, that is, an intensity reduction of 90%
10 db
159
a (dB) = ac (db/cm) x L (cm)
attenuation
160
attenuation coefficient increases, attenuation _______.
increases
161
attenuation increases with _______ frequency.
increasing
162
in soft tissues, there is approximately _____dB of attenuation per centimeter for each megahertz of frequency for a longitudinal wave
.5
163
a = 1/2 f (MHz) x L (cm)
attenuation
164
equal to the fraction of the intensity (at the beginning of the path) that remains at the end of the path
intensity ratio
165
Penetration decreases while frequency ______.
increases
166
Intensities of the echo and transmitted sound depend on:
incident intensity at boundary
impedances of the media on either side of the boundary
167
Impedance increases if density or propagation speed ______.
increases
168
z = pc
impedance
169
average soft tissue impedance
1,630,000 rayls
170
IRC depends on _____
impedances
171
IRC = R / I = z2 - z1 / z2 + z1 ^2
intensity reflection coefficient
172
the greater the differences in impedances the _____ the echo
stronger
173
ITC = T/I = 1 - IRC
intensity transmission coefficient
174
if ITC increases, IRC
decreases
175
if impedances are equal than _____
no echo
176
Reflection angle always equals the _______.
incidence angle
177
No refraction occurs if propagation speeds are ______.
equal
178
2 requirements for refraction to occur
oblique incidence
different propagation speeds
179
Most contrast agents contain
microbubbles of gas
180
In soft tissue, the round trip time is ___ us for each centimeter of depth.
13
181
D (mm) = 1/2 [c x pulse round trip time]
range equation
182
a wave is a traveling variation in quantities called wave _____.
variables
183
sound is a traveling variation in quantities called _____ variables.
acoustic
184
acoustic variables include ______, _______, and particle motion.
pressure, density
185
The wavelength of a 7-MHz ultrasound in soft tissues is ____.
.22
186
It takes __ us for ultrasound to travel 1.54 cm in soft tissue.
10
187
If propagation speed is doubled and frequency is held constant, the wavelength is ______.
doubled
188
if frequency in soft tissue is doubled, propagation speed is ______.
unchanged
189
if wavelength is 2mm and frequency is doubled, the wavelenth becomes ____.
1
190
The second harmonic of 3 MHz is ____ MHz.
6 MHz
191
Odd harmonics of 2 MHz are ______ MHz.
6, 10, 14
192
Even harmonics of 2 MHZ are _____ MHz.
4, 8, 12
193
If the density of a medium is 1000 kg/cm3 and the propagation speed is 1540 m/s, the impedance is ____ rayls.
1,540,000
194
If the wavelength is 2mm, the SPL for a three-cycle pulse is ____ mm.
6
195
the SPL in soft tissue for a two-cycle pulse of frequency 5 MHz is ____ mm.
.6
196
The PD in soft tissue for a two-cycle pulse of frequency 5 MHz is ____us.
.4
197
For a 1-kHz PRF, the PRP is _____ ms.
1
198
How many cycles are there in 1 second of continuous wave 5 MHz ultrasound?
5.000,000
199
how many cycles are there in 1-seecond of pulsed 5 MHz ultrasound with a DF of .01 (1%)?
none of the above
