The flashcards below were created by user
Qwizdom100
on FreezingBlue Flashcards.
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pressure, density, and particle vibration; sound wave quantities that vary in space and time
acoustic variables
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region of low density and pressure in a compressional wave
rarefaction
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reduction in differences between small and large amplitudes. region of high density and pressure in a wave
compression
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wave in which the particle motion is parallel to the direction of wave travel (compressional wave)
longitudinal wave
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number of cycles per second
frequency
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unit of frequency, one cycle per second; unit of pulse repetition frequency, one pulse per second.
hertz
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T/F
A wave is a traveling variation of some quantity or quantities.
True
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T/F
Sound is a traveling variation of acoustic variables.
True
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T/F
Acoustic variables include pressure, density, and particle motion.
True
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T/F
A cycle is one complete variation in pressure or other acoustic variable.
True
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T/F
Frequency is the number of cycles in a wave that occur in 1 second.
True
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One hertz is one cycle per second. The abbreviation for hertz is Hz.
True
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T/F
One kilohertz is 1000 cycles per second. The abbreviation for kilohertz is kHz.
True
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T/F
One megahertz is one million cycles per second. The abbreviation for megahertz is MHz.
True
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sound of frequency too low for human hearing (<20 hertz)
Infrasound
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sound of frequency too high for human hearing (>20,000 hertz)
Ultrasound
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imaging depth
penetration
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the common unit for period in ultrasound
microsecond (μs)
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Period = 1/Frequency
T (μs) = 1 / f (MHz)
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If frequency increases, period _______.
decreases
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length of space over which a cycle occurs
wavelength
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T/F
Wavelength is commonly expressed in millimeters.
True
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the speed with which a wave moves through a medium
propagation speed
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Wavelength is = propagation speed (c) divided by frequency
λ (mm) = c (mm/μs) / f (MHz)
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If frequency increases, wavelength ______.
decreases
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the resistance of a material to compression
stiffness
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Propagation speeds are highest in ______ and lowest in ______.
- solids (highest)
- gases (lowest)
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Propagation speed values in soft tissue range from _____ to _____.
1.44 to 1.64 mm/μs
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The average propagation speed of sound in tissue is _____.
1.54 mm/μs
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progression of travel
propagation
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sound propagation in which the propagation speed depends on pressure causing the wave to shape to change and harmonics to be generated
nonlinear propagation
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the primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics
fundamental frequency
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frequencies that are even and odd multiples of another, commonly called fundamental or operating frequency
harmonics
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a wave in which cycles repeat indefinitely; not pulsed.
continuous wave
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ultrasound produced in pulsed form by applying electric pulses or voltages of one or a few cycles to the transducer
pulsed ultrasound
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a brief excursion of a quantity from its normal value; a few cycles
pulse
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T/F
With continuous wave ultrasound, cycles repeat indefinitely. Pulsed ultrasound consists of pulses separated by gaps in time. A pulse is a few cycles of ultrasound.
True
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number of pulses per second
pulse repetition frequency or pulse repetition rate
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interval of time from the beginning of one pulse to the beginning of the next
pulse repetition period
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PRF is commonly expressed in
kilohertz
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PRP is commonly expressed in
milliseconds
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If pulse repetition frequency increases, pulse repetition period ______.
decreases
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Interval of time from beginning to end of a pulse
pulse duration
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T/F
Shorter pulses, compared with longer ones, improve the quality of sonographic images.
True
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T/F
Sonographic pulses are typically 2 or 3 cycles long. Doppler pulses are typically 5 to 30 cycles long.
True
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Pulse duration = period (time for one cycle) X number of cycles in the pulse (n)
PD (μs) = n X T (μs)
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T/F
Pulse duration is the time for a pulse to occur.
True
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T/F
If frequency is increased, period is decreased, reducing pulse duration. If the number of cycles in a pulse is reduced, pulse duration is decreased.
True
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fraction of time that pulsed ultrasound is on
duty factor
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T/F
Longer pulses increase the duty factor because the sound is on more of the time.
True
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DF = PD (μs) / PRP (μs)
DF =( PD (μs) X PRF (kHz) ) / 1000 (kHz / MHz)
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T/F
If pulse duration increases, duty factor ______.
increases
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if PRF increases, pulse repetition period _____ and duty factor ________.
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length of space over which a pulse occurs
spatial pulse length
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Spatial pulse length = length of each cycle X the number of cycles in the pulse
SPL (mm) = n X λ (mm)
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T/F
Spatial pulse length is the length of space that a pulse takes up.
True
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T/F
If the number of cycles in a pulse increases, spatial pulse length increases. If frequency increases wavelength and spatial pulse length decrease.
True
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T/F
Shorter pulses improve sonographic image resolution.
True
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range of frequencies contained in an ultrasound pulse; range of frequencies within which a material, device, or system can operate.
bandwidth
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bandwidth divided by operating frequency
fractional bandwidth
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nonspecific term referring to amplitude or intensity
strength
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maximum variation of an acoustic variable or voltage
amplitude
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power divided by area
intensity
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rate at which work is done; rate at which energy is transferred
power
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T/F
If beam power increases, intensity increases. If beam area decreases (focusing), intensity increases.
True
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force multiplied by displacement
work
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conversion of sound to heat
absorption
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decrease in amplitude and intensity with distance as a wave travels through a medium
attenuation
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portion of sound returned from a media boundary; echo
reflection
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diffusion or redirection of sound in several directions upon encountering a particle suspension or a rough surface
scattering
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unit of power or intensity ratio; the number of decibels is 10 times the logarithm (to the base 10) of the power or intensity ratio.
decibel
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attenuation per centimeter of wave travel
attenuation coefficient
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time it takes a wave to vibrate a single cycle
period
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Period is determined by the ________ _______.
sound source
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the number of particular events that occur in a specific duration of time. in ultrasound, the number of cycles that occur in one second
frequency
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Diagnostic range of frequency in ultrasound
2 MHz - 10 MHz
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Frequency is determined by the ______ _______.
sound source
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Frequency and period have what type of relationship
inversely proportional and a reciprocal relationship
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distance or length of one complete cycle
wavelength
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wavelength is determined by the ______ ______ and the _____.
sound source and medium
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shorter wavelengths produce ______ quality images
higher
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frequency and wavelength have a _______ relationship as long as they are in the same medium
inverse
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the distance that a sound wave travels through a medium in 1 second
propagation speed
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propagation speed is determined by the
medium
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order the medium that sound travels the fastest in (normal states of matter)
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2 medium characteristics that affect propagation speed
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propagation speed and stiffness are ______ related
directly
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other name for stiffness
bulk modulus
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propagation speed and density are ______ related
inversely
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the difference in the maximum value and the average or undisturbed value of an acoustic variable may also be the difference between the minimum and the average
amplitude
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amplitude is _______ by the sonographer
adjustable
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the difference between the maximum and minimum values of an acoustic variable
peak-to-peak amplitude
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rate of energy transfer
power
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power is measured in
watts
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power is _____ by the sonographer
adjustable
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power is ______ to the amplitude ______
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concentration of energy in a sound beam
intensity
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intensity = power/cross sectional area
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Intensity is measured in
watts/cm ^2
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intensity is _______ by the sonographer
adjustable
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intensity and power are ________
proportional
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intensity is proportional to the amplitude _______
squared
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What parameters describe pulsed sound?
- pulse duration
- pulse repetition period
- pulse repetition frequency
- duty factor
- spatial pulse length
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the actual time from the start of a pulse to the end of that pulse
pulse duration
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pulse = # cycles X period
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pulse duration = # cycles / frequency
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pulse duration is ______ to the number of cycles in the pulse
proportional
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pulse duration is ______ proportional to the period
directly
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Pulse duration is _______ proportional to the frequency
directly
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long pulses have either
- many cycles
- individual cycles with long periods
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short pulses have either
- few cycles in the pulse
- individual cycles with short periods
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clinical imaging uses pulses that contain how many cycles
2-4
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distance from the start of a pulse to the end of that pulse
spatial pulse length
-
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SPL is ______ proportional to the number of cycles
directly
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SPL is ______ proportional to the wavelength
directly
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SPL is _______ proportional to frequency
inversely
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The major difference between SPL and PD
- SPL refers to distance
- PD refers time
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time from the start of one pulse to the start of the next pulse . includes the pulse duration and the listening time
PRP
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PRP is related to the ____ of view
depth
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PRP and imaging depth are ______ related
directly
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the number of pulses that are transmitted into the body each second
Pulse repetition frequency
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depth of view and PRF are ______ related
inversely
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PRP and PRF are _______ related and ______
inversely related and reciprocals
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seconds (PRP) go with hertz (PRF)
milliseconds (PRP) go with ______ (PRF)
kilohertz
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the percentage of time or fraction of time that the system is transmitting a pulse
duty factor
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duty factor% = (pulse duration / PRP) X 100
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a duty factor of 1 would refer to a ______ wave
continuous wave
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a duty factor of 0 means the system is _____
off
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duty factor is _____ related to imaging depth
inversely
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What are the 7 parameters required to completely characterize a sound wave?
- period
- frequency
- wavelength
- speed
- amplitude
- power
- intensity
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tissue/material through which the sound waves travel
medium
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3 parameters describe the size, magnitude, or strength of a sound wave
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10^9 giga G billion
10^6 mega M million
10^3 kilo k thousand
10^2 hecto h hundred
10^1 deca da ten
10^-1 deci d tenth
10^-2 centi c hundredth
10^-3 milli m thousandth
10^-6 micro µ millionth
10^-9 nano n billionth
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