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Which axis on a graph runs horizontally?
x-axis
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Which axis on a graph runs vertically?
y-axis
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Def. two items that are not associated
unrelated
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Def. two items that are associated such that when one item increases, the other increases
directly related or directly proportional
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Def. two items that are associated or affiliated. However, the relationship between the two does not have to be specified
related or proportional
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Def. two items are associated such that when one item increases, the other decreases
inversely related or inversely proportional
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Def. when two numbers with a reciprocal relationship are multiplied together, the result is one. This is a special form of inverse relationship.
Reciprocal relationship
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Name the Powers of Ten for the metric system up to billion and billionth. Include the Exponent, Prefix, Symbol, and Meaning
- 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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What units correspond with length?
cm, feet, etc.
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What units correspond with area?
cm^2, ft^2, etc.
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What units correspond with volume?
cm^3, ft^3, etc.
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What type of energy are sound waves?
mechanical
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Pressure is measured in what units?
pascals (Pa)
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Density is measured in units of what?
kg/cm^3
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Distance is measured in units of what?
cm, mm, ft, miles, etc.
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Name are the 3 accoustic variables.
pressure, density, distance
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What are the 7 accoustic parameters?
- period
- frequency
- amplitude
- power
- intensity
- wavelength
- propagation speed
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Def. particles move in a direction that is perpendicular (at right angles) to the direction that the wave propagates
transverse waves
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Def. particles move in the same direction the the wave propagates
longitudinal waves
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Def. when a pair of waves peak (maximum value) occur at the same time and at the same location. similarly, the troughs (minimum values) occur at the same time
in-phase
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Def. peaks or troughs of two waves occur at different times
out-of-phase
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Def. when two waves combine to form a single wave
interference
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Def. the interference of a pair of in-phase waves results in the formation of a single wave of greater amplitude than either of its components
constructive interference
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Def. the interference of a pair of out-of-phase waves results in the formation of a single wave of lesser amplitude than either of its components
destructive interference
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What type of interference occurs when the frequencies of the waves differ?
both constructive and destructive interference will occur
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What do waves transfer from one location to another?
energy
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Describe sound waves.
sound waves are a series of compressions and rarefactions
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Two waves are traveling in a medium and arrive at a location at the same time. What event takes place?
interference
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Which types of waves will exhibit both constructive and destructive interference?
waves of different frequency
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Def. describe the features of a sound wave.
parameters
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What is the source of a sound wave in US?
the ultrasound system and transducer
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Def. the time it takes a wave to vibrate a single cycle, or the time from the start of a cycle to the start of the next cycle
Period
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Period is reported in units of what?
milliseconds
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What are the typical values for period in ultrasound?
.1-.5 µs
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What determines the period?
the sound source only
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Can the period be adjusted by the sonographer?
no
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Def. the number of particular events that occurs in a specific duration of time
frequency
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What does hertz mean?
per second
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Frequency is reported in what unit?
hertz which = 1 cycle/per second
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What are the typical values for hertz in ultrasound?
2 MHz - 10 MHz
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Frequency is determined by what?
the sound source only
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Can the sonographer adjust frequency?
no
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What is the audible range of human hearing?
20 Hz to 20,000 Hz
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Def. sound below 20 Hz which is below the threshold for human hearing
infrasound
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Sound above 20,000 Hz which is above the threshold for human hearing
ultrasound
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Why is frequency important in diagnostic sonography?
frequency affects penetration and image quality
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What is the relationship between period and frequency?
inversely related and they are also reciprocals
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What 3 parameters describe the size, strength, or magnitude of the sound wave?
amplitude, power, intensity
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Def. describes the "bigness" of a wave. it is the difference between the maximum value and the average or undisturbed value of an acoustic variable. (also the difference of the minimum value and average value)
amplitude
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Amplitude can be in units of what?
any of the acoustic variables (pressure, density, particle motion) also relatively in decibels
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What is the typical value in ultrasound for pressure amplitude?
1 MPa to 3 MPa
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Amplitude is determined by what?
initially the sound source but it decreases as the sound propagates which depends on the characteristics of the medium and sound wave
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Can the sonographer adjust amplitude?
yes
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How is amplitude measured?
it's measured from the middle value to the maximum value
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How is peak-to-peak amplitude measured?
the difference between maximum and minimum values of an acoustic variable
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Def. the rate of energy transfer or the rate at which work is performed describes the "bigness" of the sound wave
power
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Power is measured in what?
watts
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What is the typical value for power in ultrasound?
4 to 90 milliwatts
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What determines power?
initially the sound source but it decreases as the sound propagates which depends on the characteristics of the medium and sound wave
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Can the sonographer adjust power?
yes
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What is the relationship between power and amplitude?
- direct relationship
- power is proportional to the wave's amplitude squared
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Def. the concentration of energy in a sound beam. it relates to how the power in a wave spreads or is distributed in space. describes the sounds "bigness"
intensity
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Intensity is measured in units of what?
watts/square centimeter
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What are the typical values for intensity in ultrasound?
.01 to 300 W/cm^2
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How is intensity determined?
initially the sound source but it decreases as the sound propagates which depends on the characteristics of the medium and sound wave
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Can the sonographer adjust intensity?
yes
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All three "bigness" parameters (amplitude, power, intensity) are ______ related.
directly
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What is relationship between intensity and power?
power and intensity are directly proportional
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What is the relationship between intensity and amplitude?
intensity is directly proportional to amplitude squared
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Def. the distance or length of one complete cycle
wavelength
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Wavelength is measured in units of what?
mm, meters, etc.
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What are typical values for wavelength?
.15 to .8 mm
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What determines wavelength?
source and medium
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Can the sonographer adjust wavelength?
no
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What is the relationship between wavelength and frequency?
inversely proportional
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What is the rule that defines the relationship between frequency and wavelength of sound in soft tissue?
To find wavelength of a sound wave in soft tissue, divide 1.54 mm by the frequency in MHz
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Why is wavelength important in diagnostic ultrasound?
shorter wavelengths produce higher quality images with greater detail
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Def. the distance that a sound wave travels through a medium in 1 second
propagation speed
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Propagation speed is measured in units of what?
meters per second, mm/µs, etc.
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What are the typical values for propagation speed in ultrasound?
500 m/s to 4000 m/s depending on the tissue
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What determines propagation speed?
determined by the medium only
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Can the sonographer adjust propagation speed?
no
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What is the speed of sound in soft tissue?
1,540 m/s
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What characteristics of a medium determine the speed of sound in that medium?
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Def. describes the ability of an object to resist compression.
stiffness
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Def. describes the relative weight of a material
density
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How does stiffness affect speed?
stiffness and speed are directly related
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How does density affect speed?
density and speed are inversely related
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Elasticity and compressiblity refer to what type of media?
non-stiff
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What 5 additional parameters describe pulsed sound?
- pulse duration
- pulse repetition period
- pulse repetition frequency
- duty factor
- spatial pulse length
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Def. a collection of cycles that travel together with a beginning and move as a single unit
-
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What are the two components of pulsed ultrasound?
- transmit, talking, "on" time
- receive, listening, "off" time
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Def. the actual time from the start of a pulse to the end of that pulse with a fixed duration
pulse duration
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What are typical values for pulse duration?
.3 to 2 µs
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What determines pulse duration?
the sound source
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What are the formulas for pulse duration?
pulse duration (µs) = # cycles X period
pulse duration (µs) = # cycles / frequency (MHz)
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What characteristics create pulses with long durations?
- many cycles in a pulse
- individual cycles with long periods
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What characteristics create pulses with long durations?
- few cycles in the pulse
- individual cycles with short periods
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Which type of pulse is more desirable in diagnostic imaging, and why?
shorter duration pulses because they create images with greater accuracy
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Def. the distance a pulse occupies in space from the start to the end of a pulse
spatial pulse length
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What are typical values for spatial pulse length?
.1 to 1 mm
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What determines spatial pulse length?
sound source and medium
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What is the formula for spatial pulse length?
SPL (mm) = # cycles X wavelength (mm)
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Spatial pulse length is:
______ proportional to the number of cycles in the pulse
______ proportional to wavelength
______ proportional to frequency
- directly
- directly
- inversely
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What are the characteristics of short and long pulses?
- Long:
- many cycles in the pulse
- cycles with longer wavelengths
- Short
- fewer cycles in the pulse
- cycles with shorter wavelengths
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Which type of pulse is the most desirable in diagnostic imaging?
shorter pulses because they create more accurate images
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Def. the time from the start of one pulse to the start of the next pulse
pulse repetition period
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What units are pulse repetition period reported in?
units of time (ms)
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What are some typical values of pulse repetition period?
100 µs - 1 ms
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What determines pulse repetition period?
- sound source
- specifically imaging depth
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How are pulse repetition period and depth of view related?
- directly related
- prp increases depth of view increases
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What are the two components of pulse repetition period?
- transmit time
- receive time
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What is the other name for transmit time?
pulse duration
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When sonographers adjust the depth what are they actually adjusting?
listening time
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How does listening time change with depth?
depth increases listening time increases
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Def. the number of pulses that an US system transmits into the body each second
Pulse Repetition Frequency
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Typical value of PRF?
1000 - 10,000 hertz
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PRF determined by?
- sound source
- specifically max imaging depth
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PRF and imaging depth are ____ related.
inversely
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Increasing depth will do what to PRF?
lower PRF
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An US machine is imaging to a depth of 2 cm. How would the PRF be described?
high
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When the depth is increased to 20 cm, what happens to PRF?
PRF is reduced
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How are PRP and PRF related?
inversely and reciprocals
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Formula for PRF and PRP
PRF X PRP = 1
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