Ultrasound Physics Final
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Ultrasound Physics Final
Edelman Chapters 13
Name the Metric System from Billion to Billionth
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
What is an appropriate unit for area?
What is an appropriate unit for volume?
How many milliliters are in 8 liters?
How many centimeters are in 3 meters?
How many kilometers are in 3000 meters?
What is the reciprocal of 100?
1/100 or 0.01
What is the reciprocal of 1/8?
How many hertz is 3 MHz?
How many milliliters are contained in a jar filled with 5 liters of fluid?
How many liters are contained in 80 ml of fluid?
How many times bigger is a thousand than ten?
How much bigger is a billion than a million?
How much smaller is a hundred than a thousand?
Def. biologic tissue
All waves carry _____ from one location to another.
Sound is a _____ wave in which particles in the medium move.
Def. Area of increased pressure (squeezed together)
Def. Area of decreased pressure (stretched apart)
Sound waves travel in _____ lines.
Sound waves are ______ waves.
Def. the effects of the medium upon the sound wave
acoustic propagation properties
Def. the effects of the sound wave upon the biologic tissue through which it passes
Name the acoustic variables
pressure, density, distance
What is pressured measured in?
Def. concentration of force in an area
Def. concentration of mass in a volume
Def. measure of particle motion
What is density measured in?
What is distance measured in?
ft, cm, mile, etc...
What are the acoustic parameters?
Def. particles that move in a direction that is perpendicular to the direction that the wave propagates
Def. particles that move in the same direction that the wave propagates
Def. when the peaks or troughs of a pair of waves occur at the same time
Def. when the peaks or troughs of a pair of waves occur at different times
Def. when a pair of waves lose their individual characteristics and combine to form a single wave
Def. the interference of a pair of in-phase waves
Def. the interference of a pair of out-of-phase waves
Waves of with different ______ will undergo constructive and destructive interference.
Two waves are traveling in a medium and arrive at a location at the same time. What event takes place?
interference (we don't know if they are in-sync)
What is the source of a sound wave?
ultrasound system and transducer
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
What is period measured in?
seconds, ms, hours, etc...
What are the typical values for period?
.1µs to .5µs
Def. the number of particular events that occurs in a specific duration of time
What is frequency measured in?
What are the typical values for frequency?
2 MHz to 10 MHz
Def. less than 20 Hz
Def. between 20 Hz to 20 kHz
Def. greater than 20 kHz
What are the relationships between period and frequency?
What are the bigness parameters?
Def. the difference between the maximum or minimum value and the average or undisturbed value of an acoustic variable
What units can amplitude be measured in?
What are the typical values of amplitude?
1 MPa to 3 MPa
Def. the difference between maximum and minimum values of an acoustic variable
Def. the rate of energy transfer or the rate at which work is performed
What is power measured in?
What are the typical values of power?
4 - 90 milliwatts
How is power and amplitude related?
power is proportional to amplitude squared
How is intensity and amplitude related?
intensity is proportional to amplitude squared
How is intensity and power related?
intensity is proportional to power
Amplitude has increased by a factor of 3. How much has the power changed?
Amplitude has decreased by 1/2. How much has power changed?
Def. the concentration of energy in a sound beam
What is intensity measured in?
What are the typical values of intensity?
.01 - 300 W/cm^2
What is the formula for intensity?
intensity (W/cm^2) = power (w) / area (cm^2)
Def. the distance or length of one complete cycle
What is wavelength measured in?
meters, inches, cm, etc...
What are the typical values of wavelength?
.15 - .8 mm
What determines wavelength?
sound source and medium
What is the formula between wavelength and frequency?
wavelength (mm) = 1.54 mm/µs / frequency (MHz)
What type of wavelength creates better images?
Def. the distance that a sound travels through a medium in 1 second
What is propagation speed measured in?
meters per second, mm/µs
What are the typical values of propagation speed?
500 m/s to 4000 m/s
What determines the propagation speed?
What is the speed of sound in soft tissue?
What is the formula for speed of sound?
speed (m/s) = frequency (Hz) x wavelength (m)
What two characteristics of a medium effect the speed of sound?
stiffness and density
Def. describes the ability of an object to resist compression
Def. describes the relative weight of a material
What is the relationship between stiffness and speed?
What is the relationship between density and speed?
What terms can describe stiffness? They are opposite of stiff.
elasticity and compressiblity
What acoustic parameters are determined by the sound source?
period, frequency, amplitude, power, intensity, wavelength
What acoustic parameters are reciprocals?
period and frequency
What acoustic parameters can be adjusted by the sonographer?
amplitude, power, intensity
What acoustic parameter is determined by both the sound source and the medium?
What acoustic parameter is determined by the medium only?
T/F A wave with a frequency of 15,000 MHz is ultrasonic?
T/F If amplitude is increased to 3 times it's original value, intensity is increased 6-fold.
T/F If power is halved intensity is reduced by 1/4.
false it's halved
T/F propagation speed increases as frequency increases.
Medium 1 has a density of 9 and a stiffness of 6.
Medium 2 has a density of 8 and a stiffness of 6.
Which medium will be slower?
If the power in a beam is 1 watt and the area is 5 cm^2, what is the beam's intensity?
If intensity remains the same while the power is doubled, what has happened to the beam area?
A sound beam travels a total of 10 cm in 2 seconds. What is the speed of sound?
T/F Propagation speed increases as frequency increases.
T/F Propagation speed increases as frequency decreases.
T/F Propagation speed does not change as frequency increases.
What is the wavelength of 3 MHz sound in soft tissue?
The effects of sound waves on tissue in the body are called ______.
The effects of tissue on sound waves are called ______.
Acoustic propagation properties
The effects of a medium on an ultrasound wave are called ________.
acoustic propagation properties
T/F Continuous wave sound can create diagnostic images.
false pulse sound
What is pulsed sound?
a collection of cycles that travel together
2 components of pulsed sound
transmit, talking, "on" time
receive, listening, "off" time
Def. the actual time from the start of a pulse to the end of that pulse
What is pulse duration measured in?
seconds, µs, ms, etc...
What are the typical values of pulse duration?
.3µs to 2µs
What are the formulas for pulse duration?
pulse duration (µs) = # of cycles x period (µs)
pulse duration (µs) = # of cyles / frequency (MHz)
What are the 2 characteristics of long duration pulses?
many cycles in the pulse
individual cycles with long periods
What are the 2 characteristics of short duration pulses?
few cycles in the pulse
individual cycles with short periods
Which type of pulse duration is desirable for imaging?
shorter duration pulses improve image accuracy
Def. the distance from the start to the end of a pulse
Spatial Pulse Length
What is spatial pulse length measured in?
mm, inches, etc...
What are the typical values for spatial pulse length?
.1 to 1 mm
What is the formula for spatial pulse length?
spatial pulse length (mm) = # of cycles x wavelength (mm)
What are 2 characteristics of long pulse length?
many cycles in the pulse
cycles with longer wavelengths
What are the 2 characteristics of short pulse length?
fewer cycles in the pulse
cycles with shorter wavelengths
Which type of spatial pulse length is more desirable?
shorter pulses create more accurate images
Def. the time from the start of one pulse to the start of the next pulse
Pulse Repetition Period
What is pulse repetition period measured in?
units of time, ms
What are the typical values for pulse repetition period?
100µs to 1 ms
Pulse repetition period is controlled by what?
Sound source specifically imaging depth
Def. the maximum distance into the body that an ultrasound system is imaging
Depth of View
What are the 2 components of pulse repetition period?
What is transmit time also known as?
What happens to the depth of view when the listening time and pulse repetition period lengthen?
What happens to the depth of view when the listening time and pulse repetition period shorten?
Def. the number of pulses that an ultrasound system transmits into the body each second
Pulse Repetition Frequency
What is pulse repetition frequency measured in?
What are the typical values of pulse repetition frequency?
1000 to 10000 hertz
How is pulse repetition frequency and depth of view related?
What are the relationships between pulse repetition frequency and pulse repetition period?
inversely related and reciprocals
What is the easiest formula to remember PRF and PRP?
PRF x PRP = 1
T/F Two waves can have identical pulse repetition frequencies , even if their pulse repetition periods are different.
T/F Two waves can have identical PRFs, even if their periods are different.
T/F PRF and PRP are determined only by the imaging depth.
Def. the percentage or fraction of time that the system is transmitting a pulse
What is unit for duty factor?
none. it's a percentage therefore dimensionless
What are the typical values for Duty Factor?
.2% to .5%
What is the relationship between depth of view and duty factor?
What is the formula for duty factor?
duty factor (%) = (pulse duration / PRP) x 100
What are the factors that determine shallow imaging?
higher duty factor
What are the factors that determine deeper imaging?
lower duty factor
Def. refers to the intensity of the beam at different locations or distances
Def. the maximum intensity
Def. the mathematical middle intensity
Def. refers to the intensity at all time, transmit and receive
Def. refers to the intensity at the transmit time
Def. the beams intensity at the location where it is maximum
spatial peak intensity
Def. the beams intensity across the entire cross-sectional area
spatial average intensity
Def. the beams intensity at the instant in time of its maximum value
Def. the average intensity during the most intense half-cycle
Def. the average intensity during the pulse duration
pulse average intensity
Def. averaging the intensity during the entire PRP (includes both the transmit and recieve times)
temporal average intensity
T/F Intensities may be reported in various ways with respect to time and space.
The different measurements of intensities are important in the study of ________.
______ intensity is the most relevant intensity with respect to tissue heating.
What units are all intensities are measured in?
What intensity if the highest and which is the lowest?
SPTP is the highest
SATA is the lowest
Def. describes the spread of a beam in space
beam uniformity coefficient or SP/SA factor
Def. describes the relationship of beam intensities with time
Continuous wave ultrasound. The pulse average and temporal average intensities are the ______.
T/F For continuous wave ultrasounds, SPTA = SPPA and SATA = SAPA.
T/F When pulsed and continuous waves have the same SPTP, the continous wave will have the higher intensity.
T/F When pulsed and continuous waves have the same SATP intensities, the continuous wave will have the higher SPTA intensity.
Rank the types of intensities from largest to smallest.
SPTP > Im > SPPA > SPTA > SATA
Def. the weakening of sound as it travels in the body
Def. strengthening of the ultrasound signal
Def. the unit that quantifies the strength of sound beams as they are created by tranducers and travel through the body
Def. Decibels that are increasing in strength or getting larger.
Def. decibels that are decreasing in strength or getting smaller
The 3 decibel rule.
a change of 3 decibel is equal to doubling or having the intensity of the ultrasound beam
The 10 decibel rule.
a change of 10 decibels it equal to 10-fold or one-tenth of the intensity of the ultrasound beam
A reduction in the intensity of a sound beam to one-half of its original value is _____dB.
A reduction in the intensity of a sound beam to one-quarter of its original value is ______ dB.
-10 dB means that the intensity is reduced to ______ of its original value.
dB is a mathematical representation with a ______ scale.
logarithmic and relative
T/F We need one intensity to calculate dB.
A wave's intensity is 2mW/cm^2. There is a change of +9 dB. What is the final intensity?
2 factors determine attenuation
frequency of sound
3 processes contribute to attenuation
Def. when the wave's energy strikes a boundary and is redirected back toward the sound source
2 types of reflection
specular and diffuse
Def. type of reflection when sound is reflected back by a smooth boundary and in only one direction
Def. type of reflection when sound is reflected back by and irregular surface and radiates in more than one direction
Def. random redirection of sound in many directions that occurs when the tissue interface is smaller or equal to the wavelength of the sound beam
Def. a special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength and the sound wave is redirected equally in all directions
Def. occurs when ultrasonic energy is converted into another energy form, such as heat
Def. the number of decibels of attenuation that occurs when sound travels one cm
What is the attenuation coefficient measured in?
What is the formula for total attenuation?
total attenuation (dB) = atten coefficient (dB/cm) x distance (cm)
What is the formula for attenuation coefficient in soft tissue?
atten. coef. (dB/cm) = frequency (MHz) / 2
Def. the distance that sound travels in a tissue that reduces the intensity of sound to one-half its original value
half-value layer thickness
What are typical values for half-value layer thickness?
.25 - 1 cm
What are synomyns for half-value layer?
penetration depth, depth of penetration, half-boundary layer
2 factors that determine half-value layer thickness
the frequency of sound
Def. the acoustic resistance to sound traveling in a medium
What is the formula for impedance?
impedance (rayls) = density (kg/m^3) x prop. speed (m/s)
What unit is impedance measured in?
What are the typical values for impedance?
1.25 to 1.75 Mrayls
What is another name for acoustic impedance?