Absorption
conversion of sound to heat
Acoustic
Having to do with sound
Acoustic Variable
Pressure, density, and particle vibration: sound wave quantities that vary in space and time.
Amplitude
Maximum variation of an acoustic variable or voltage
Attenuation
Decrease in amplitude and intensity with distance as a wave travels through a medium
Attenuation Coefficient
Attenuation per centimeter of wave travel
Backscatter
Sound scattered back in the direction from which it came
Bandwidth
Range of frequencies contained in an ultrasound pulse; range of frequencies within which a material, device, or system can operate.
Compression
Reduction in differences between small and large amplitude. Region of high density and pressure in a compressional wave
Constructive Interference
Combination of positive or negative pressures
Continuous Wave
CW
A wave in which cycles repeat indefinitely; not pulsed
Contrast Agent
A suspension of bubbles or particles introduced into circulation to enhance the contrast between anatomical structures, thereby improving their imaging
Coupling Medium
A gel used to provide a good sound path between echoes of slightly different intensities
Cycle
One complete variation of an acoustic variable
Decibel
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
Density
Mass divided by volume
Destructive Interference
Combination of positive and negative pressures
Duty Factor
Fraction of time that pulsed ultrasound is on
Echo
Reflection
Energy
capability to do work
Fractional Bandwidth
Bandwidth divided by operating frequency
Frequency
Number of cycles per second
Fundamental Frequency
The primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics
Harmonics
Frequencies that and odd multiples of another
sometimes called Fundamental or operating Frequency
Hertz
Hz
Unit of frequency, one cycle per second; units of pulse repetition frequency, one pulse per minute
Impedance
Density multiplied by the sound propagation speed
Incidence Angle
Angle between incident sound direction and a line perpendicular to the boundary of a medium
Intensity
Power divided by area
Intensity Reflection Coefficient
Reflected intensity divided by incident intensity; the fraction of incident intensity reflected
Intensity Transmission Coefficient
Transmitted intensity divided by incident intensity; the fraction of incident intensity transmitted into the second medium
Interference
Combination of positive and/or negative pressure
Kilohertz
kHz
One thousand hertz
Longitudinal Wave
Wave in which the particle motion is parallel to the direction of wave travel
Medium
material through which a wave travels
Megahertz
MHz
One million hertz
Nonlinear propagation
Sound propagation in which the propagation speed depends on pressure causing the wave shape to change and harmonics to be generated
Oblique Incidence
Sound direction that is not perpendicular to the media boundaries
Penetration
imaging depth
Period
time per cycle
Perpendicular
Geometrically related to 90 degrees
Perpendicular Incidence
Sound direction that is perpendicular to the boundary between media
Power
Rate at which work is done; rate ate which energy is transferred
Pressure
force divided by an area in a fluid
Propagation
progression or travel
Propagation Speed
Speed at which a wave moves through a medium
Pulse
A brief excursion of a quantity from it's normal value; a few cycles
Pulse Duration
Interval of time from beginning to end of a pulse
Pulse Repetition Frequency
PRF
Number of pulses per second; sometimes called pulse repetition rate
Pulse Repetition Period
Interval of time from the beginning of one pulse to the beginning of the next
Pulsed Ultrasound
Ultrasound produced in pulsed form by applying electric pulses or voltage of on or a few cycles to the transducer
Range Equation
relationship between round-trip pulse travel time, propagation speed, and distance to a reflector
Rarefaction
region of low density and pressure in a compressional wave
Rayl
unit of impedence
Reflection
portion of a sound returned from a media boundary; echo
Reflection Angle
Angle between the reflected sound direction and a line perpendicular to the media boundary
Reflector
Media boundary that produces a reflection; reflecting surface
Refraction
change of sound direction on passing from one media to another
Scatterer
AN object that scatters sound because of its small size or its surface roughness
Scattering
Diffusion or redirection of sound in several directions upon encountering a particle suspension or rough surface
Sound
traveling wave of acoustic variable
Spatial Pulse Length
length of space over which a pulse occurs
Speckle
The granular appearance of images and spectral displays that is caused by the interference of echos from the distribution of scatterers in tissue
Specular Reflection
Reflection from large (relative to wavelength), flat, smooth boundary
Stiffness
Property of a medium; applied pressure divided b the fractional volume change produced by the pressure
Strength
Non specific term referring to amplitude or intensity
Transmission Angle
Angle between the transmitted sound direction and a line perpendicular to the media
Ultrasound
A form of sound
Sound that has a higher frequency than the sound we can hear
Over 20 kHz
Wave
is a traveling variation in one or more quantities, such as Pressure
Wavelength
length of space over which a cycle occurs
Work
Force multiplied by displacement
A wave is a traveling variations in quantities called wave _________________.
A) length
B) variables
C) cycles
D) periods
B) variables
Sound is a traveling variations in quantities called _________________ variables.
A) wave
B) pressure
C) density
D) acoustic
D) acoustic
Ultrasound is a sound with a frequency greater than ____________ Hz.
A) 2
B) 15
C) 20,000
D) 1540
C) 20,000
Acoustic variables include __________________, ____________, and particle vibration.
A) stiffness, density
B) hardness, impedance
C) amplitude, intensity
D) pressure, density
D) pressure, density
Which of the following frequencies is in the ultrasound range?
A) 12 Hz
B) 15,0000 Hz
C) 15 kHz
D) .004 MHz
D) .004 MHz
Which of the following is not an acoustic variable?
A) Pressure
B) Propagation speed
C) Density
D) Particle Motion
B) Propagation speed
Frequency is the number of ______________ an acoustic variable goes through in a second.
A) cycles
B) amplitude
C) pulse lengths
D) duty factors
A) cycles
The unit of frequency is ________________, which is abbreviated _______________.
A) hertz, Hz
B) megahertz, mHz
C) kilohurts, khts
D) cycles, cps
A) hertz, Hz
Period is the _________that it takes for one cycle to occur.
A) length
B) amplitude
C) time
D) height
C) time
Period decreases as _____________ increases.
A) wavelength
B) pulse length
C) frequency
D) bandwidth
C) frequency
Wavelength is the length of ________________ over which one cycle occurs.
A) time
B) space
C) propagation
D) power
B) space
Propagation speed is the speed with which a(n) ___________ moves though a medium.
A) wave
B) particle
C) frequency
D) attenuation
A) wave
Wavelength is equal to _______________, ____________ divided by ___________.
A) propagation speed, frequency
B) media density, stiffness
C) pulse length, frequency
D) wave amplitude, period
A) propagation speed, frequency
The _______________ and _____________ of a medium determine propagation speed.
A) amplitude, intensity
B) wavelength, period
C) impedance, attenuation
D) density, stiffness
D) density, stiffness
Propagation speed increases if ____________ is increased.
A) amplitude
B) frequency
C) density
D) stiffness
D) stiffness
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
B) 1540, 1.54
Propagation speed is determined by the ___________.
A) frequency
B) amplitude
C) wavelength
D) medium
D) medium
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
C) gas, liquid, solid
The wavelength of 7 MHz ultrasound in soft tissue is ___________________ mm.
A) 1.54
B) .54
C) .22
D) 33.33
C) .22
(λ=1.54/7)
Wavelength in soft tissue _________ as frequency increases.
A) is constant
B) decreases
C) increases
D) weakens
B) decreases
It takes _______ μs for ultrasound to travel 1.54 cm in soft tissue
A) 10
B) .77
C) 1.54
D) 100
A) 10
Propagation speed in bone is ____________ that in soft tissue.
A) lower than
B) equal to
C) higher than
D) 10 m/s greater than
C) higher than
Sound travels fastest in ________________.
A) air
B) helium
C) water
D) steel
D) steel
Solids have higher propagation speeds than liquids because they have greater ____________.
A) density
B) stiffness
C) attenuation
D) propagation speed
B) stiffness
Sound travels slowest in _______________.
A) gases
B) liquids
C) tissue
D) bone
A) gases
Sound is a ________ ________ wave.
mechanical, longitudinal
If propagation speed is doubled (a different medium) and frequency is held constant, the wave-length is _________________.
doubled
If frequency in soft tissue is doubled, propagation speed _________________.
unchanged
If wavelength becomes 2 mm and frequency is doubled the wavelength becomes _______________mm.
1
Waves can carry ____________ from one place to another.
information
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
C) Wavelength
True or False?
If two media have different stiffnesses, the one with the higher stiffness will have the higher propagation speed.
True
The second harmonic of 3 MHz is ________________.
6
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
D) 6, 10, 14
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
C) 4, 8, 12
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
E) more than one of the above
C) propagation speed depends on pressure
D) the waveform changes shape as it travels
As a wave changes from sinusoidal form to sawtooth form, additional _____________ appear that are ______ and _________ multiples of the __________. They are called ________________.
Frequency, even , odd, fundamental, harmonics
If Density of a mediu is 1000 kg/m^3 and the propagation speed is 1540 m/s, the impedance is _________ rayls
1,540,000
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.
True
If two media have the same density but different propagation speeds, the one with the higher propagation speed will have the higher impedance.
True
Impedance is _______________ multiplied by __________ ____________.
Density, propagation speed
The abbreviation CW stands for _______________.
Continuous wave
Pulse repetition frequency is the number of _________ occurring in 1 second.
Pulses
Pulse repetition _______________ is the time from the beginning of one pulse to the beginning of the next.
Period
Pulse repetition period _________________ as pulse repetition frequency increases.
Decreases
Pulse duration is the _________________ it takes for a pulse to occur.
time
Spatial pulse length is the ___________ of ___________ that a pulse occupies as it travels.
length, space
_________________ ________________ is the fraction of time that pulse ultrasound is actually on.
Duty factor
Pulse duration equals the number of cycles in the pulse multiplied by __________________.
Period
Spatial pulse length equals the number of cycles in the pulse multiplied by __________________.
wavelength
The duty factor of continuous wave sound is ______________.
1 (100%)
If the length is 2 mm, the spatial pulse length for a three-cycle pulse is ______________ mm.
6
3 cycles x 2 mm
The spatial pulse length in soft tissue for a two-cycle pulse of frequency 5 MHz is _____________ mm.
.616
(1.54 mm/μs x 2) / 5 MHz
The pulse duration in soft tissue for a two-cycle pulse of frequency 5 MHz is _______________ μs.
.4
2 / 5 MHz
For a 1-kHz pulse repetition frequency, the pulse repetition period is ________________ ms.
1
1 /1 kHz
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 ____________________.
.0004 (.04%)
.4 μs x .001 μs = .0004
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
D) 5,000,000
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
E) none of the above
5,000,000 x .01 = 50,000
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%
C) 99%
For pulsed ultrasound, the duty factor is always ____________ __________________ one.
less than
_____________ is a typical duty factor for sonography.
A) .1
B) .5
C) .7
D) .9
A) .1
Amplitude is the maximum _________ that occurs in an acoustic variable.
variation
Intensity is the ________________ in a wave divided by ________________.
Power, area
The unit for intensity _____________.
W/cm^2
Intensity is proportional to _____________ squared.
amplitude
If power is doubled and area remains unchanged, intensity is _______________.
doubled
If area is doubled and power remains unchanged intensity is ________________.
halved
If both power and area are doubled, intensity is ___________.
unchanged
If amplitude is doubled, intensity is ______________.
quadrupled
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.
5 mW/cm^2
10mW/2cm2= 5
Attenuation is the reduction in _____________ and _______________ as a wave travels through a medium.
amplitude, intensity
Attenuation consists of _______________, ______________, and ______________.
absorption, reflection, scattering
The attenuation coefficient is attenuation per ____________ of sound travel.
centimeter
Attenuation and the attenuation coefficient are given in units of _____________ and _______________ respectively.
dB. dB/cm
For soft tissues, there is approximately ___________ dB of attenuation per centimeter for each megahertz of frequency.
.5 dB
3 MHz/.5dB
For soft tissue the attenuation coefficient at 3 MHz is approximately ________________.
1.5 dB/cm
The attenuation coefficient in soft tissue __________ as frequency increases
increases
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 __________________.
doubled, doubled, quadrupled
If frequency is doubled and path length is halved attenuation is ________________.
unchanged
Absorption is the conversion _________ to _______________.
sound, heat
Can absorption be greater than attenuation in a given medium at a given frequency?
No
Is attenuation in bone higher or lower than in soft tissue?
higher
The imaging depth (penetration) ____________ as frequency increases.
decreases
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
.32
(.5 * 4 MHz) * 4cm = 8 dB attenuation
intensity ratio is .16 * 2 W/cm2 = .32 W/cm2
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
.000 000 02
(.5 *40 MHz) * 4 cm = 80 dB attenuation
.000 000 01 * 2 W/cm2 = .000 000 02 W/cm2
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
C) .8 cm
.5 * 7.5 MHz * .8 cm = 3 dB
When ultrasound encounters a boundary with perpendicular incidence, two ___________ of the tissue must be different to produce a reflection (echo).
impedances
With perpendicular incidence, two media _____________ and the incident ____________ must be known to calculate the reflected intensity.
impedances, intensity
with perpendicular incidence, two media ___________ must be known to calculate the intensity reflection coefficient.
impedances
For an incident intensity of 2 mW/cm^2 and impedances of 49 and 51 rayle, the reflected intensity is ____________ mW/cm^3
.0008, 1.9992
True or False
If the impedance of the media are equal, there is not reflection.
True
for perpendicular incidence
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
D) b and c
B) impedance difference
C) impedance sum
Refraction is a change in ______________ of sound when it crosses a boundary, Refreaction is caused by a change in __________ ____________ at the boundary.
Direction Propagation speed
Under what two conditions does refraction not occur?
Perpendicular incidence, equal media propagation speeds
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.
32
Redirection of sound in many directions as it encounters rough media junctions or particle suspensions (heterogeneous media) is called __________.
scattering
True or False?
Back scatter helps make echo reception less dependent on incident angle.
True
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
D) travel time and speed
No reflection will occur with perpendicular incidence if the media ________________ are equal.
impedances
True or False?
Scattering occurs at smooth boundaries and within homogeneous media.
False