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Chapter 2 Ultrasound Terms

front 1

Absorption

back 1

conversion of sound to heat

front 2

Acoustic

back 2

Having to do with sound

front 3

Acoustic Variable

back 3

Pressure, density, and particle vibration: sound wave quantities that vary in space and time.

front 4

Amplitude

back 4

Maximum variation of an acoustic variable or voltage

front 5

Attenuation

back 5

Decrease in amplitude and intensity with distance as a wave travels through a medium

front 6

Attenuation Coefficient

back 6

Attenuation per centimeter of wave travel

front 7

Backscatter

back 7

Sound scattered back in the direction from which it came

front 8

Bandwidth

back 8

Range of frequencies contained in an ultrasound pulse; range of frequencies within which a material, device, or system can operate.

front 9

Compression

back 9

Reduction in differences between small and large amplitude. Region of high density and pressure in a compressional wave

front 10

Constructive Interference

back 10

Combination of positive or negative pressures

front 11

Continuous Wave

back 11

CW

A wave in which cycles repeat indefinitely; not pulsed

front 12

Contrast Agent

back 12

A suspension of bubbles or particles introduced into circulation to enhance the contrast between anatomical structures, thereby improving their imaging

front 13

Coupling Medium

back 13

A gel used to provide a good sound path between echoes of slightly different intensities

front 14

Cycle

back 14

One complete variation of an acoustic variable

front 15

Decibel

back 15

Unit of power or intensity ratio; the number of decibels is 10 times the logarithm (to the 10 base) of the power or intensity ratio

front 16

Density

back 16

Mass divided by volume

front 17

Destructive Interference

back 17

Combination of positive and negative pressures

front 18

Duty Factor

back 18

Fraction of time that pulsed ultrasound is on

front 19

Echo

back 19

Reflection

front 20

Energy

back 20

capability to do work

front 21

Fractional Bandwidth

back 21

Bandwidth divided by operating frequency

front 22

Frequency

back 22

Number of cycles per second

front 23

Fundamental Frequency

back 23

The primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics

front 24

Harmonics

back 24

Frequencies that and odd multiples of another

sometimes called Fundamental or operating Frequency

front 25

Hertz

back 25

Hz

Unit of frequency, one cycle per second; units of pulse repetition frequency, one pulse per minute

front 26

Impedance

back 26

Density multiplied by the sound propagation speed

front 27

Incidence Angle

back 27

Angle between incident sound direction and a line perpendicular to the boundary of a medium

front 28

Intensity

back 28

Power divided by area

front 29

Intensity Reflection Coefficient

back 29

Reflected intensity divided by incident intensity; the fraction of incident intensity reflected

front 30

Intensity Transmission Coefficient

back 30

Transmitted intensity divided by incident intensity; the fraction of incident intensity transmitted into the second medium

front 31

Interference

back 31

Combination of positive and/or negative pressure

front 32

Kilohertz

back 32

kHz

One thousand hertz

front 33

Longitudinal Wave

back 33

Wave in which the particle motion is parallel to the direction of wave travel

front 34

Medium

back 34

material through which a wave travels

front 35

Megahertz

back 35

MHz

One million hertz

front 36

Nonlinear propagation

back 36

Sound propagation in which the propagation speed depends on pressure causing the wave shape to change and harmonics to be generated

front 37

Oblique Incidence

back 37

Sound direction that is not perpendicular to the media boundaries

front 38

Penetration

back 38

imaging depth

front 39

Period

back 39

time per cycle

front 40

Perpendicular

back 40

Geometrically related to 90 degrees

front 41

Perpendicular Incidence

back 41

Sound direction that is perpendicular to the boundary between media

front 42

Power

back 42

Rate at which work is done; rate ate which energy is transferred

front 43

Pressure

back 43

force divided by an area in a fluid

front 44

Propagation

back 44

progression or travel

front 45

Propagation Speed

back 45

Speed at which a wave moves through a medium

front 46

Pulse

back 46

A brief excursion of a quantity from it's normal value; a few cycles

front 47

Pulse Duration

back 47

Interval of time from beginning to end of a pulse

front 48

Pulse Repetition Frequency

back 48

PRF

Number of pulses per second; sometimes called pulse repetition rate

front 49

Pulse Repetition Period

back 49

Interval of time from the beginning of one pulse to the beginning of the next

front 50

Pulsed Ultrasound

back 50

Ultrasound produced in pulsed form by applying electric pulses or voltage of on or a few cycles to the transducer

front 51

Range Equation

back 51

relationship between round-trip pulse travel time, propagation speed, and distance to a reflector

front 52

Rarefaction

back 52

region of low density and pressure in a compressional wave

front 53

Rayl

back 53

unit of impedence

front 54

Reflection

back 54

portion of a sound returned from a media boundary; echo

front 55

Reflection Angle

back 55

Angle between the reflected sound direction and a line perpendicular to the media boundary

front 56

Reflector

back 56

Media boundary that produces a reflection; reflecting surface

front 57

Refraction

back 57

change of sound direction on passing from one media to another

front 58

Scatterer

back 58

AN object that scatters sound because of its small size or its surface roughness

front 59

Scattering

back 59

Diffusion or redirection of sound in several directions upon encountering a particle suspension or rough surface

front 60

Sound

back 60

traveling wave of acoustic variable

front 61

Spatial Pulse Length

back 61

length of space over which a pulse occurs

front 62

Speckle

back 62

The granular appearance of images and spectral displays that is caused by the interference of echos from the distribution of scatterers in tissue

front 63

Specular Reflection

back 63

Reflection from large (relative to wavelength), flat, smooth boundary

front 64

Stiffness

back 64

Property of a medium; applied pressure divided b the fractional volume change produced by the pressure

front 65

Strength

back 65

Non specific term referring to amplitude or intensity

front 66

Transmission Angle

back 66

Angle between the transmitted sound direction and a line perpendicular to the media

front 67

Ultrasound

back 67

A form of sound

Sound that has a higher frequency than the sound we can hear

Over 20 kHz

front 68

Wave

back 68

is a traveling variation in one or more quantities, such as Pressure

front 69

Wavelength

back 69

length of space over which a cycle occurs

front 70

Work

back 70

Force multiplied by displacement

front 71

A wave is a traveling variations in quantities called wave _________________.

A) length
B) variables
C) cycles
D) periods

back 71

B) variables

front 72

Sound is a traveling variations in quantities called _________________ variables.

A) wave
B) pressure
C) density
D) acoustic

back 72

D) acoustic

front 73

Ultrasound is a sound with a frequency greater than ____________ Hz.

A) 2
B) 15
C) 20,000
D) 1540

back 73

C) 20,000

front 74

Acoustic variables include __________________, ____________, and particle vibration.

A) stiffness, density
B) hardness, impedance
C) amplitude, intensity
D) pressure, density

back 74

D) pressure, density

front 75

Which of the following frequencies is in the ultrasound range?

A) 12 Hz
B) 15,0000 Hz
C) 15 kHz
D) .004 MHz

back 75

D) .004 MHz

front 76

Which of the following is not an acoustic variable?

A) Pressure
B) Propagation speed
C) Density
D) Particle Motion

back 76

B) Propagation speed

front 77

Frequency is the number of ______________ an acoustic variable goes through in a second.

A) cycles
B) amplitude
C) pulse lengths
D) duty factors

back 77

A) cycles

front 78

The unit of frequency is ________________, which is abbreviated _______________.

A) hertz, Hz
B) megahertz, mHz
C) kilohurts, khts
D) cycles, cps

back 78

A) hertz, Hz

front 79

Period is the _________that it takes for one cycle to occur.

A) length
B) amplitude
C) time
D) height

back 79

C) time

front 80

Period decreases as _____________ increases.

A) wavelength
B) pulse length
C) frequency
D) bandwidth

back 80

C) frequency

front 81

Wavelength is the length of ________________ over which one cycle occurs.

A) time
B) space
C) propagation
D) power

back 81

B) space

front 82

Propagation speed is the speed with which a(n) ___________ moves though a medium.

A) wave
B) particle
C) frequency
D) attenuation

back 82

A) wave

front 83

Wavelength is equal to _______________, ____________ divided by ___________.

A) propagation speed, frequency
B) media density, stiffness
C) pulse length, frequency
D) wave amplitude, period

back 83

A) propagation speed, frequency

front 84

The _______________ and _____________ of a medium determine propagation speed.

A) amplitude, intensity
B) wavelength, period
C) impedance, attenuation
D) density, stiffness

back 84

D) density, stiffness

front 85

Propagation speed increases if ____________ is increased.

A) amplitude
B) frequency
C) density
D) stiffness

back 85

D) stiffness

front 86

The average propagation speed in soft tissue ___________m/s or ______________ mm/μs.

A) 10, 3
B) 1540, 1.54
C) 3, 10
D) 1.54, 1540

back 86

B) 1540, 1.54

front 87

Propagation speed is determined by the ___________.

A) frequency
B) amplitude
C) wavelength
D) medium

back 87

D) medium

front 88

Place the following in order of increasing sound propagation speed:

A) gas, solid liquids
B) solid, liquid, gas
C) gas, liquid, solid
D) liquid, solid, gas

back 88

C) gas, liquid, solid

front 89

The wavelength of 7 MHz ultrasound in soft tissue is ___________________ mm.

A) 1.54
B) .54
C) .22
D) 33.33

back 89

C) .22

(λ=1.54/7)

front 90

Wavelength in soft tissue _________ as frequency increases.

A) is constant
B) decreases
C) increases
D) weakens

back 90

B) decreases

front 91

It takes _______ μs for ultrasound to travel 1.54 cm in soft tissue

A) 10
B) .77
C) 1.54
D) 100

back 91

A) 10

front 92

Propagation speed in bone is ____________ that in soft tissue.

A) lower than
B) equal to
C) higher than
D) 10 m/s greater than

back 92

C) higher than

front 93

Sound travels fastest in ________________.

A) air
B) helium
C) water
D) steel

back 93

D) steel

front 94

Solids have higher propagation speeds than liquids because they have greater ____________.

A) density
B) stiffness
C) attenuation
D) propagation speed

back 94

B) stiffness

front 95

Sound travels slowest in _______________.

A) gases
B) liquids
C) tissue
D) bone

back 95

A) gases

front 96

Sound is a ________ ________ wave.

back 96

mechanical, longitudinal

front 97

If propagation speed is doubled (a different medium) and frequency is held constant, the wave-length is _________________.

back 97

doubled

front 98

If frequency in soft tissue is doubled, propagation speed _________________.

back 98

unchanged

front 99

If wavelength becomes 2 mm and frequency is doubled the wavelength becomes _______________mm.

back 99

1

front 100

Waves can carry ____________ from one place to another.

back 100

information

front 101

From given values for propagation speed and frequency, which of the following can be calculated?

A) Amplitude
B) Impedance
C) Wavelength
D) A and B
E) B and C

back 101

C) Wavelength

front 102

True or False?

If two media have different stiffnesses, the one with the higher stiffness will have the higher propagation speed.

back 102

True

front 103

The second harmonic of 3 MHz is ________________.

back 103

6

front 104

The odd harmonics of 2 MHz are ________________.

A) 1, 3, 5
B) 2, 4, 6
C) 6, 9, 12
D) 6, 10, 14
E) 10, 12, 14

back 104

D) 6, 10, 14

front 105

The even harmonics of 2 MHz are ___________.

A) 1, 3, 5
B) 2, 4, 6
C) 4, 8, 12
D) 6, 10, 14
E) 10, 12, 14

back 105

C) 4, 8, 12

front 106

Nonlinear propagation means ________________.

A) the sound beam does not travel in a straight line
B) propagation speed depends on frequency
C) propagation speed depends on pressure
D) the waveform changes shape as it travels
E) more than one of the above

back 106

E) more than one of the above

C) propagation speed depends on pressure
D) the waveform changes shape as it travels

front 107

As a wave changes from sinusoidal form to sawtooth form, additional _____________ appear that are ______ and _________ multiples of the __________. They are called ________________.

back 107

Frequency, even , odd, fundamental, harmonics

front 108

If Density of a mediu is 1000 kg/m^3 and the propagation speed is 1540 m/s, the impedance is _________ rayls

back 108

1,540,000

front 109

True or False?

If two media have the same propagation speed but different densities, the one with the higher density will have the higher impedance.

back 109

True

front 110

If two media have the same density but different propagation speeds, the one with the higher propagation speed will have the higher impedance.

back 110

True

front 111

Impedance is _______________ multiplied by __________ ____________.

back 111

Density, propagation speed

front 112

The abbreviation CW stands for _______________.

back 112

Continuous wave

front 113

Pulse repetition frequency is the number of _________ occurring in 1 second.

back 113

Pulses

front 114

Pulse repetition _______________ is the time from the beginning of one pulse to the beginning of the next.

back 114

Period

front 115

Pulse repetition period _________________ as pulse repetition frequency increases.

back 115

Decreases

front 116

Pulse duration is the _________________ it takes for a pulse to occur.

back 116

time

front 117

Spatial pulse length is the ___________ of ___________ that a pulse occupies as it travels.

back 117

length, space

front 118

_________________ ________________ is the fraction of time that pulse ultrasound is actually on.

back 118

Duty factor

front 119

Pulse duration equals the number of cycles in the pulse multiplied by __________________.

back 119

Period

front 120

Spatial pulse length equals the number of cycles in the pulse multiplied by __________________.

back 120

wavelength

front 121

The duty factor of continuous wave sound is ______________.

back 121

1 (100%)

front 122

If the length is 2 mm, the spatial pulse length for a three-cycle pulse is ______________ mm.

back 122

6

3 cycles x 2 mm

front 123

The spatial pulse length in soft tissue for a two-cycle pulse of frequency 5 MHz is _____________ mm.

back 123

.616

(1.54 mm/μs x 2) / 5 MHz

front 124

The pulse duration in soft tissue for a two-cycle pulse of frequency 5 MHz is _______________ μs.

back 124

.4

2 / 5 MHz

front 125

For a 1-kHz pulse repetition frequency, the pulse repetition period is ________________ ms.

back 125

1

1 /1 kHz

front 126

The pulse duration in soft tissue for a two-cycle pulse of frequency 5 MHz is _______________ μs.

For a 1-kHz pulse repetition frequency, the pulse repetition period is ________________ ms.

The duty factor is ____________________.

back 126

.0004 (.04%)

.4 μs x .001 μs = .0004

front 127

How many cycles are there in a 1 second of continuous wave 5-MHz ultrasound.

A) 5
B) 500
C) 5000
D) 5,000,000
E) none of the above

back 127

D) 5,000,000

front 128

How many cycles are there in a 1 second of pulsed 5-MHz ultrasound with a duty factor of .01 (1%).

A) 5
B) 500
C) 5000
D) 5,000,000
E) none of the above

back 128

E) none of the above

5,000,000 x .01 = 50,000

front 129

How many cycles are there in a 1 second of pulsed 5-MHz ultrasound with a duty factor of .01 (1%).

How many cycles did pulsing eliminate?

A) 100%
B) 99.9%
C) 99%
D) 50%
E) 1%

back 129

C) 99%

front 130

For pulsed ultrasound, the duty factor is always ____________ __________________ one.

back 130

less than

front 131

_____________ is a typical duty factor for sonography.

A) .1
B) .5
C) .7
D) .9

back 131

A) .1

front 132

Amplitude is the maximum _________ that occurs in an acoustic variable.

back 132

variation

front 133

Intensity is the ________________ in a wave divided by ________________.

back 133

Power, area

front 134

The unit for intensity _____________.

back 134

W/cm^2

front 135

Intensity is proportional to _____________ squared.

back 135

amplitude

front 136

If power is doubled and area remains unchanged, intensity is _______________.

back 136

doubled

front 137

If area is doubled and power remains unchanged intensity is ________________.

back 137

halved

front 138

If both power and area are doubled, intensity is ___________.

back 138

unchanged

front 139

If amplitude is doubled, intensity is ______________.

back 139

quadrupled

front 140

If a sound beam has a power of 10 mW and a beam area of 2 cm^2, the spatial average intensity is __________________ mW/cm^2.

back 140

5 mW/cm^2

10mW/2cm2= 5

front 141

Attenuation is the reduction in _____________ and _______________ as a wave travels through a medium.

back 141

amplitude, intensity

front 142

Attenuation consists of _______________, ______________, and ______________.

back 142

absorption, reflection, scattering

front 143

The attenuation coefficient is attenuation per ____________ of sound travel.

back 143

centimeter

front 144

Attenuation and the attenuation coefficient are given in units of _____________ and _______________ respectively.

back 144

dB. dB/cm

front 145

For soft tissues, there is approximately ___________ dB of attenuation per centimeter for each megahertz of frequency.

back 145

.5 dB

3 MHz/.5dB

front 146

For soft tissue the attenuation coefficient at 3 MHz is approximately ________________.

back 146

1.5 dB/cm

front 147

The attenuation coefficient in soft tissue __________ as frequency increases

back 147

increases

front 148

For soft tissue, if frequency is doubled, attenuation is ________________. If path length is doubled attenuation is ________________. If both frequency and path length are doubled, attenuation is __________________.

back 148

doubled, doubled, quadrupled

front 149

If frequency is doubled and path length is halved attenuation is ________________.

back 149

unchanged

front 150

Absorption is the conversion _________ to _______________.

back 150

sound, heat

front 151

Can absorption be greater than attenuation in a given medium at a given frequency?

back 151

No

front 152

Is attenuation in bone higher or lower than in soft tissue?

back 152

higher

front 153

The imaging depth (penetration) ____________ as frequency increases.

back 153

decreases

front 154

If intensity of 4-MHz ultrasound entering soft tissue is 2 W/cm^2, the intensity at a depth of 4 cm is ______________W/cm^2

back 154

.32

(.5 * 4 MHz) * 4cm = 8 dB attenuation
intensity ratio is .16 * 2 W/cm2 = .32 W/cm2

front 155

If the intensity of 40-MHz ultrasound entering soft tissue is 2 W/cm^2, the intensity at a depth of 4 cm is ______________ W/cm^2

back 155

.000 000 02

(.5 *40 MHz) * 4 cm = 80 dB attenuation
.000 000 01 * 2 W/cm2 = .000 000 02 W/cm2

front 156

The depth at which half-intensity occurs in soft tissue at 7.5 MHz is _________________.

A) .6 cm
B) .7 cm
C) .8 cm
D) .9 cm
E) 1.0 cm

back 156

C) .8 cm

.5 * 7.5 MHz * .8 cm = 3 dB

front 157

When ultrasound encounters a boundary with perpendicular incidence, two ___________ of the tissue must be different to produce a reflection (echo).

back 157

impedances

front 158

With perpendicular incidence, two media _____________ and the incident ____________ must be known to calculate the reflected intensity.

back 158

impedances, intensity

front 159

with perpendicular incidence, two media ___________ must be known to calculate the intensity reflection coefficient.

back 159

impedances

front 160

For an incident intensity of 2 mW/cm^2 and impedances of 49 and 51 rayle, the reflected intensity is ____________ mW/cm^3

back 160

.0008, 1.9992

front 161

True or False

If the impedance of the media are equal, there is not reflection.

back 161

True

for perpendicular incidence

front 162

With perpendicular incidence, the reflected intensity depends on the _________________.

A) density difference
B) impedance difference
C) impedance sum
D) b and c
E) a and b

back 162

D) b and c

B) impedance difference
C) impedance sum

front 163

Refraction is a change in ______________ of sound when it crosses a boundary, Refreaction is caused by a change in __________ ____________ at the boundary.

back 163

Direction Propagation speed

front 164

Under what two conditions does refraction not occur?

back 164

Perpendicular incidence, equal media propagation speeds

front 165

The low speed of sound in fat is a source of image degradation because of refraction. If incidence angle at a boundary between fat (1.45 mm/μs) is 30 degrees, the transmission angle is ______________ degrees.

back 165

32

front 166

Redirection of sound in many directions as it encounters rough media junctions or particle suspensions (heterogeneous media) is called __________.

back 166

scattering

front 167

True or False?

Back scatter helps make echo reception less dependent on incident angle.

back 167

True

front 168

What must be known to calculate the distance to a reflector?

A) attenuation, speed, and density
B) attenuation and impedance
C) attenuation and absorption
D) travel time and speed
E) density and speed

back 168

D) travel time and speed

front 169

No reflection will occur with perpendicular incidence if the media ________________ are equal.

back 169

impedances

front 170

True or False?

Scattering occurs at smooth boundaries and within homogeneous media.

back 170

False