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PHYSICS > Chapter 2 Kremkau > Flashcards

Chapter 2 Kremkau Flashcards

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1
Q

conversion of sound to heat

A

absorption

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2
Q

derived from the Greek word for hearing

A

Acoustic

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3
Q

pressure, density, and particle vibrations

A

acoustic variables

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4
Q

indicators of the strength of sound, related to how loud the sound would be if it could be heard

A

amplitude

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5
Q

the weakening of sound while it propagates

A

attenuation

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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

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7
Q

decibels per centimeter

A

attenuation

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8
Q

sound scattered back in the direction from which it originally came

A

backscatter

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9
Q

range of frequencies

A

bandwith

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10
Q

the shorter the pulse, the _____ the bandwidth

A

broader

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11
Q

regions of high pressure and density

A

compression

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12
Q

echoes that arrive at transducer in such a way that they reinforce each other

A

constructive interference

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13
Q

ultrasound in which cycles repeat indefinitely

A

continuous wave

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14
Q

liquid suspensions that are injected into the circulation intravenously are used to increase echogenicity

A

contrast agents

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15
Q

a gel that is used to provide a good sound path from the transducer

A

coupling medium

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16
Q

pressure and density increase and decrease, and particles of the medium oscillate in motion

A

cycle

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17
Q

units used to quantify attenuation

A

decibel

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18
Q

the concentration of matter
(mass per unit volume)

A

density

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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

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20
Q

the fraction of time that pulsed ultrasound is on. Indicates how much of the time the ultrasound is on

A

duty factor

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21
Q

the reflected and scattered sound waves

A

echo

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22
Q

the ability to accomplish work

A

energy

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23
Q

bandwidth divided by operating frequency. Unitless. Describes how large the bandwidth is compared with operating frequency

A

fractional bandwidth

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24
Q

expresses the number of cycles in a wave that occur in 1 second

A

frequency

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25
Q

original frequency

A

fundamental frequency

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26
Q

any other wave shape containing additional frequencies that are even and odd multiples of the original frequency

A

harmonics

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27
Q

one cycle per second

A

hertz

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28
Q

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

A

impedance

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29
Q

unit for impedance

A

Rayl

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30
Q

the direction of travel with respect to the boundary given

A

incidence angle

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31
Q

the rate at which energy passes through a unit area

A

intensity

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32
Q

dividing the reflected (echo) intensity by the incident intensity that is reflected

A

intensity reflection coefficient

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33
Q

dividing the transmitted intensity by the incident yields the fraction of the incident intensity that is transmitted into the second medium

A

intensity transmission coefficient

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34
Q

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

A

interference

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35
Q

1,000 Hz

A

Kilohertz

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36
Q

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.

A

Longitudinal wave

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37
Q

a thing that sound propagates through

A

medium

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38
Q

1,000,000 Hz

A

Megahertz

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39
Q

propagation in which speed depends on pressure and the shape of the wave changes

A

nonlinear propagation

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40
Q

when the incident sound beam encounters the boundary between two mediums at an angle

A

oblique incidence

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41
Q

half-value depth for the specific ultrasound frequency

A

penetration

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42
Q

the time is takes for one cycle to occur

A

period

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43
Q

denotes a direction of travel of the ultrasound wave perpendicular to the boundary between the two media

A

perpendicular incidence

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44
Q

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.

A

Power

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45
Q

Units of Power

A

Watts and MilliWatts

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46
Q

sound is a traveling variation in _______.

A

pressure

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47
Q

the speed at which a particular value of an acoustic variable moves, at which a cycle moves, and at which the entire wave moves

A

propagation

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48
Q

the speed with which a wave moves through a medium

A

propagation speed

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49
Q

ultrasound pulse is a few cycles of ultrasound. They are separated in time with gaps of no ultrasound

A

pulse

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50
Q

the time it takes for one pulse to occur. Equal to period times the number of cycles in the pulse. Expressed in microseconds

A

pulse duration

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51
Q

the number of pulses that occur in 1 second

A

pulse-repetition frequency

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52
Q

refers to the time from the beginning of one pulse to the beginning of the next. Its common units are milliseconds.

A

Pulse-repetition period

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53
Q

not on continuously. a few cycles of ultrasound

A

pulsed ultrasound

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54
Q

the distance to a reflector calculated from the propagation speed and pulse-round trip travel time

A

range equation

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55
Q

regions of low pressure and density

A

rarefaction

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56
Q

return of the sound wave back to the transducer

A

reflection

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57
Q

a change in acoustic impedance across a boundary between tissues

A

refraction

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58
Q

cellular tissues or particle suspensions such a blood

A

scatterer

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59
Q

the redirection of sound in many directions by rough surfaces (sometimes called diffuse scattering) or by heterogeneous media

A

scattering

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60
Q

transverse wave

A

shear wave

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61
Q

the length of a pulse from front to back. Equal to the length of each cycle times the number of cycles in the pulse

A

Spatial pulse length

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62
Q

a form of acoustic noise in sonographic imaging

A

speckle

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63
Q

a type of surface reflectance often described as a mirrorlike reflection of light from the surface

A

specular reflection

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64
Q

the resistance of a material to compression

A

stiffness

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65
Q

related to how loud the sound would be if it could be heard. Amplitude and intensity are indicators

A

strength

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66
Q

depends on propagation speeds in the media

A

transmission angle

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67
Q

shear wave

A

transverse wave

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68
Q

frequency higher than the range of human hearing

A

ultrasound

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69
Q

a traveling variation in one or more quantities called wave variables

A

wave

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70
Q

the length of space that one cycle takes up

A

wavelength

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71
Q

sound of a frequency too low for human hearing

A

infrasound

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72
Q

if frequency increases, period _______.

A

decreases

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73
Q

if frequency increases, wavelength _______.

A

decreases

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74
Q

Highest propagation speeds

A

solids

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75
Q

lowest propagation speeds

A

gases

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76
Q

average propagation speed in soft tissues

A

1.54 mm/us

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77
Q

If PRF increases, PRP ________.

A

decreases

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78
Q

Sonographic pulses are typically __-__ cycles long

A

2-3

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79
Q

Doppler pulses are typically __-__ cycles long

A

5-30

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80
Q

If frequency increases, pulse duration _______.

A

decreases

81
Q

If the number of cycles in a pulse is decreased, pulse duration is _______.

A

decreases

82
Q

If the pulse duration increases, the duty factor ______.

A

increases

83
Q

If PRF increases, duty factor _______.

A

increases

84
Q

if the number of cycles in a pulse increases, SPL ______.

A

increases

85
Q

_______ pulses improve sonographic image detail resolution

A

shorter

86
Q

if beam power increases, intensity ________.

A

increases

87
Q

if attenuation coefficient increases, attenuation _______.

A

increases

88
Q

if path length increases, attenuation _______.

A

increases

89
Q

if frequency increases, attenuation ________.

A

increases

90
Q

if frequency increases, penetration ________.

A

decreases

91
Q

impedance increases if density of propagation speed ______.

A

increase

92
Q

if the difference between the impedances increases, the ITC _______.

A

increases

93
Q

if IRC increases, ITC _______.

A

decreases

94
Q

while round trip time increases, calculated reflector distance _______.

A

increases

95
Q

frequency
period
wavelength
propagation speed
amplitude
intensity

A

terms used to describe sound

96
Q

when pressure is higher, the medium is ______.

A

denser

97
Q

when pressure is lower, the medium is ________.

A

less dense

98
Q

human hearing range

A

20-20,000 Hz

99
Q

Infrasound range

A

less than 20 Hz

100
Q

Ultrasound range

A

20,000 Hz or more

101
Q

T = 1 / f

A

Period

102
Q

also known as cycle length

A

wavelength

103
Q

propagation speed units

A

m/s mm/us

104
Q

wavelength depends on ______ and ____.

A

frequency
propagation speed

105
Q

^ = c / f

A

wavelength

106
Q

Shear wave propagation speeds in soft tissues

A

.5 - 10 m/s

107
Q

rate of change of a position of an object

A

speed

108
Q

speed with direction of motion specified

A

velocity

109
Q

propagation speed depends on ______ and ______.

A

density
stiffness

110
Q

c (m/s) = elasticity / density

A

propagation speed

111
Q

increase in stiffness, _______ propagation speed

A

increases

112
Q

increase in density ______ propagation speed

A

decreases

113
Q

In nonlinear propagation, propagation speed depends on ______.

A

pressure

114
Q

PRF units

A

kHz

115
Q

PRP units

A

milliseconds

116
Q

PRP decreases, PRF _______

A

increases

117
Q

PD = n x T

A

pulse duration

118
Q

PD decreases if number of cycles in pulse _______.

A

decreases

119
Q

PD decreases if frequency _______.

A

increases

120
Q

Duty factor continuous wave

A

100%

121
Q

_______ pulses increases duty factor

A

longer

122
Q

Higher PRFs _________ DF

A

increases DF

123
Q

units of DF

A

no units

124
Q

DF = PD (us) / PRP (us) = PD (us) x PRF (kHz) / 1000 kHz/MHz)

A

Duty Factor

125
Q

Typical DFs for sonography

A

.1-1.0%

126
Q

Typical DFs for Doppler ultrasound

A

.5-5%

127
Q

SPL = ^ x n

A

Spatial pulse length

128
Q

SPL increases with _______ and ________.

A

wavelenth

129
Q

SPL increases with _______ and ________.

A

wavelength
number of cycles in the pulse

130
Q

SPL decreases with ________ frequency.

A

increasing

131
Q

units for spatial pulse length

A

mm

132
Q

shorter pulse lengths ______ resolution

A

improve

133
Q

the higher number of frequencies, the _______ the bandwidth

A

broader

134
Q

determines the number of scan lines produced per second

A

frequency

135
Q

operating frequency / bandwidth

A

quality factor

136
Q

shorter pulses have broader bandwidth and ______ QFs.

A

lower

137
Q

indicators of the strength of sound

A

amplitude and intensity

138
Q

energy transferred divided by time required to transfer energy (transfer rate)

A

power

139
Q

units for power

A

watts and milliwatts

140
Q

beam area units

A

cm squared

141
Q

intensity units

A

w/cm2 mw/cm2

142
Q

power divided by amplitude

A

Intensity

143
Q

increase in power ______ intensity

A

increases

144
Q

increase in area _______ intensity

A

decreases

145
Q

proportional to amplitude squared

A

intensity

146
Q

if amplitude is doubled, intensity is ________.

A

quadrupled

147
Q

if amplitude is halved, intensity is _______.

A

quartered

148
Q

the greatest intensity found across the beam

A

spatial peak

149
Q

the average for all values found near the center and the small values near the periphery

A

spatial average

150
Q

the greatest intensity found in the pulses as it passes by

A

temporal peak

151
Q

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

A

pulse average

152
Q

includes the “dead” time between pulses where there is zero intensity

A

temporal average

153
Q

TA = PA x DF

A

temporal average

154
Q

reduction in amplitude and intensity as sound travels through

A

attenuation

155
Q

dominant factor of attenuation

A

absorption

156
Q

attenuation coefficient units

A

db/cm

157
Q

corresponds to an intensity ratio of one-half, that is, an intensity reduction of 50%

A

3dB

158
Q

corresponds to an intensity ratio of one-tenth, that is, an intensity reduction of 90%

A

10 db

159
Q

a (dB) = ac (db/cm) x L (cm)

A

attenuation

160
Q

attenuation coefficient increases, attenuation _______.

A

increases

161
Q

attenuation increases with _______ frequency.

A

increasing

162
Q

in soft tissues, there is approximately _____dB of attenuation per centimeter for each megahertz of frequency for a longitudinal wave

A

.5

163
Q

a = 1/2 f (MHz) x L (cm)

A

attenuation

164
Q

equal to the fraction of the intensity (at the beginning of the path) that remains at the end of the path

A

intensity ratio

165
Q

Penetration decreases while frequency ______.

A

increases

166
Q

Intensities of the echo and transmitted sound depend on:

A

incident intensity at boundary
impedances of the media on either side of the boundary

167
Q

Impedance increases if density or propagation speed ______.

A

increases

168
Q

z = pc

A

impedance

169
Q

average soft tissue impedance

A

1,630,000 rayls

170
Q

IRC depends on _____

A

impedances

171
Q

IRC = R / I = z2 - z1 / z2 + z1 ^2

A

intensity reflection coefficient

172
Q

the greater the differences in impedances the _____ the echo

A

stronger

173
Q

ITC = T/I = 1 - IRC

A

intensity transmission coefficient

174
Q

if ITC increases, IRC

A

decreases

175
Q

if impedances are equal than _____

A

no echo

176
Q

Reflection angle always equals the _______.

A

incidence angle

177
Q

No refraction occurs if propagation speeds are ______.

A

equal

178
Q

2 requirements for refraction to occur

A

oblique incidence
different propagation speeds

179
Q

Most contrast agents contain

A

microbubbles of gas

180
Q

In soft tissue, the round trip time is ___ us for each centimeter of depth.

A

13

181
Q

D (mm) = 1/2 [c x pulse round trip time]

A

range equation

182
Q

a wave is a traveling variation in quantities called wave _____.

A

variables

183
Q

sound is a traveling variation in quantities called _____ variables.

A

acoustic

184
Q

acoustic variables include ______, _______, and particle motion.

A

pressure, density

185
Q

The wavelength of a 7-MHz ultrasound in soft tissues is ____.

A

.22

186
Q

It takes __ us for ultrasound to travel 1.54 cm in soft tissue.

A

10

187
Q

If propagation speed is doubled and frequency is held constant, the wavelength is ______.

A

doubled

188
Q

if frequency in soft tissue is doubled, propagation speed is ______.

A

unchanged

189
Q

if wavelength is 2mm and frequency is doubled, the wavelenth becomes ____.

A

1

190
Q

The second harmonic of 3 MHz is ____ MHz.

A

6 MHz

191
Q

Odd harmonics of 2 MHz are ______ MHz.

A

6, 10, 14

192
Q

Even harmonics of 2 MHZ are _____ MHz.

A

4, 8, 12

193
Q

If the density of a medium is 1000 kg/cm3 and the propagation speed is 1540 m/s, the impedance is ____ rayls.

A

1,540,000

194
Q

If the wavelength is 2mm, the SPL for a three-cycle pulse is ____ mm.

A

6

195
Q

the SPL in soft tissue for a two-cycle pulse of frequency 5 MHz is ____ mm.

A

.6

196
Q

The PD in soft tissue for a two-cycle pulse of frequency 5 MHz is ____us.

A

.4

197
Q

For a 1-kHz PRF, the PRP is _____ ms.

A

1

198
Q

How many cycles are there in 1 second of continuous wave 5 MHz ultrasound?

A

5.000,000

199
Q

how many cycles are there in 1-seecond of pulsed 5 MHz ultrasound with a DF of .01 (1%)?

A

none of the above

PHYSICS (26 decks)

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