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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