Ultrasound physics Chapter 3 review
Two sound beams with different frequencies are traveling in soft tissue. Which of the following statements is correct?
both beams travel at the same speed and the higher frequency beam has the shorter wavelength
If sound doesn't travel at 1,540 m/s in a medium, then the medium ____.
cannot be soft tissue
Stiffness of a medium is the opposite of its
compressibility
When the elasticity of a medium is high, the _________ is high.
compressibility
As an ultrasound wave travels through the body, its amplitude usually:
decreases
Wavelength is a measure of:
distance
If the power is doubled, the intensity is
doubled
The wavelength of the 3MHz transducer is shorter than the 6 MHz transducer
false
When the power in an acoustic beam is doubled and the cross-sectional area of the beam is halved, then the intensity of the beam is:
four times larger
Number of particular events that occur in a specific duration of time
frequency
What is the reciprocal of period?
frequency
What term describes the number of cycles that an acoustic variable completes in a second?
frequency
As a general rule, which of the following lists media in increasing order of propagation speeds?
gas, liquid, solid
Ultrasound is defined as a sound with a frequency of ____
greater than 0.02 MHz
Which of the following characteristics will create the slowest speed of sound?
high density, low stiffness
The speed of sound traveling through bone is ____ soft tissue
higher than
What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz?
humans can't hear them
What happens to the intensity of an ultrasound beam when the beam's cross-sectional area remains unchanged while the amplitude of the wave triples?
increases nine fold
Concentration of the energy of a sound beam
intensity
With standard ultrasonic imaging, what happens to the period of a wave as it propagates?
it remains the same
Mathematically, when a number is squared, the number is multiplied by:
itself
Which of the following characteristics will create the fastest speed of sound
low density, high stiffness
Propagation speed is determined by
medium
What is the best estimate of the distance that sound can travel in soft tissue in one second?
one mile
The time it takes a wave to vibrate a single cycle, or time from the start of a cycle to the start of the next cycle
period
Rate of energy transfer or rate at which work is performed
power
Intensity = ____
power/beam area
Intensity and power are related to amplitude by
proportional to amplitude squared
What is the unit for period?
seconds
Compared to soft tissue, the speed of an acoustic wave through lung tissue is _____.
slower
Power is determined by
sound source
Speed of sound (propagation speed) is defined by which of the following?
speed that a wave travels through a medium
The ability of an object to resist compression
stiffness
The wavelength of an ultrasonic wave is determined by:
the sound source and the medium through which the wave travels
What determines the initial intensity of an ultrasound beam?
the source of the sound wave
What determines the initial amplitude of a sound beam?
transducer
What are the units of intensity?
watts/cm2
If the frequency of a wave increases:
wavelength decreases because they are indirectly related
What is the typical vale for wavelength?
0.1-0.8 mm
In order to be identified as ultrasound, the frequency of a wave must be greater than
20 kHz
The maximum cyclical change in a quantity is known as
Amplitude
Amplitude is measured from
Baseline to peak
Which of the following statements about decibels (dB) is not true?
Decibels are an absolute scale of measurement
The frequency of the transducer is increased from 2.5MHz to 10MHz, what happened to the wavelength?
Decreased to 1/4 original wavelength
As the frequency of a wave doubles, the wavelength ____
Decreases by half
As sound propagations through soft tissue, the amplitude
Decreases proportional to distance
Every 3dB of change in power results in a beam with double the intensity. Increase power of 3db = Increase to double the intensity; Decrease of 3dB = Decrease intensity to one half the original value If the amplitude of the ultrasound wave decreases by 1/2 with a constant beam area, what happens to the intensity of the beam?
Decreases to 25% of original value
On an ultrasound scanner, the sonographer can change the frequency of the transducer. T/F?
False
The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer. T/F?
False
The ultrasound wave travels faster than the audible wave.
False
In which tissue is the ultrasound wavelength shortest when using a 5 MHz transducer?
Fat
Which has the slowest propagation speed?
Lung
____ is defined as energy per unit of time
Power
As the wave propagates through the tissue, the amplitude
decreases
Typically, as an ultrasound wave travels through soft tissue, the power of the wave:
decreases
Relative weight of a material
density
Which of the following terms best describes the relationship between frequency and wavelength for sound traveling in soft tissue?
inverse
Infrasound is defined as sound with a frequency of ____.
less than 20 Hz
The speed at which a wave travels through a medium is determined by:
the medium's properties only
What determines the initial amplitude of an ultrasound wave?
transducer
What determines the period of an ultrasound wave?
transducer
What establishes the frequency of an ultrasound wave?
transducer
Wave Wavelength of the ultrasound wave is a physical parameter that is described as the ____.
-Distance between successive compression zones -Distance required to complete one cycle -Acoustic velocity divided by the frequency
What is the typical value for period?
0.08-0.5 microseconds
In soft tissue, which of the following is closest to the wavelength of a 10 MHz sound wave?
0.15 millimeters
If the power in a beam is 1 watt and the area is 5cm2, the beam's intensity is
0.2 W/cm^2
What is the period for a 5 MHz transducer?
0.2 microseconds
What is the period of a 5 MHz ultrasound wave?
0.2 microseconds
The wavelength of an ultrasonic wave in tissue generated by a 3-MHz transducer is ____.
0.51 mm
What is the wavelength of a 2 MHz sound in soft tissue?
0.77 mm
What is the range of periods commonly found in waves produced by ultrasound systems?
0.8-0.5 microseconds
If the frequency is 1MHz, what is the period?
1 microsecond
What is the best estimate for the speed of sound in tendon?
1,754 m/s
Which sound waves are audible?
10 kHz
Which of the following sound waves is infrasonic?
15 Hz
The average speed of sound in soft tissue is:
1540 m/s
Usual frequency ranges in diagnostic ultrasound are
2 MHz to 15 MHz
What is the range of frequencies emitted by transducers used in ultrasonic imaging?
2,000,000 to 15,000,000 Hz
What is the standard range of audible frequencies?
20 Hz to 20,000 Hz
The maximum value of the density of an acoustic wave is 60 lb/in2 while the minimum density is 20 lb/in2. What is the amplitude of the wave?
20 lb/in2
Which of the following frequencies could be detected by the human ear?
2000 Hz
If the level of an acoustic variable ranges from 55 to 105, what is the amplitude?
25
The frequency of a transducer is 25,000,000 cycles per second. This can be written as
25 MHz
Diagnostic ultrasound is described as frequencies greater than:
2MHz
The amplitude of an acoustic wave decreases from 27 pascals to 9 pascals. If the initial power was 27 watts, what is the wave's final power?
3 watts
What is the speed of sound in air?
330 m/s
Which of the following sound waves is infrasonic?
4 Hz
Calculate the frequency for the ultrasound wave, which has a wavelength of 0.38 mm in soft tissue.
4 MHz
Which of the following sound waves is ultrasonic and most useful in diagnostic ultrasound?
4 MHz
A wave that oscillates at 40 cycles per second has a frequency of ____.
40 Hz
What is the typical value for speed
500 m/s-4000 m/s
Which of the following frequencies could be used for diagnostic ultrasound?
5MHz
Compare 2 sound waves, A and B. The frequency of wave A is 1/3 that of wave B. How does the period of wave A compare with the period of wave B?
A is 3 times as long as B
What term describes the rate of propagation of the ultrasound wave through a medium?
Acoustic velocity
With regard to amplitude, all of the following are true EXCEPT
Amplitude is difference between the maximum and the minimum values of an acoustic variable
The propagation speed used for soft tissue is:
An average based on the usual percentages of each type of tissue
If a 3.5 MHz wave is transmitted through the media listed below, the longest wavelength will be seen in the wave moving through ____.
Bone
Rank the following media in increasing order of propagation speed.
Bone, muscle, fat, lung, air
Arrange from fastest to slowest
Bone, tendons, muscles, blood, liver, soft tissue, fat, lung
Wavelength is determined by
Both the source and the medium
The property of the medium, which provides a measure of the resistance to ultrasound passing through the medium, is the ____.
Bulk modulus
Which of the following are acceptable units for the amplitude of an acoustic wave?
Cm and atmospheres
The opposite of stiffness, Increasing compressibility causes a decrease in propagation speed
Compressibility
What 2 properties establish sound's propagation speed in a given medium?
Density and stiffness
Wavelength is a measurement of ____ in units of ____
Distance in mm or cm
Wavelength is equal to the propagation speed
Divided by frequency
Stiffness of a medium is the opposite of compressibility/elasticity.
False
The propagation speed of continuous wave ultrasound is faster than pulsed wave ultrasound.
False
With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body. T/F?
False
= ____ X wavelength
Frequency
Hertz is a unit of measurement used to describe what wave characteristics?
Frequency
The number of wavelengths passing a given point in a single second is called
Frequency
The amplitude of an acoustic wave is increased. Which of the following will most likely remain unchanged?
Frequency and period
Wavelength depends on which two factors?
Frequency and propagation speed
Which of the following best describes a medium in which sound will propagate at the slowest rate?
High density and low stiffness
The formula for intensity is
I = Power (w)/ area (cm^2)
If the amplitude of the sound wave doubles, what happens to the beam intensity?
Increases by a factor of 4
Which of the following sound wave characteristics is adjustable by the Sonographer?
Intensity
If the power in an ultrasound beam is unchanged, while at the same time, the beam area doubles, then the beam's intensity:
Is halved
As sound travels in the body, what typically happens to the intensity of the wave? It increases or decreases
It decreases through attenuation
What happens to an acoustic beam's intensity when the power in the beam increases by 25% while the cross-sectional area remains the same?
It increases by 25%
Arrange from slowest of fastest
Lung, fat, soft tissue, liver, bood, muscle, tendons, bone
Wavelength is determined by
Medium and source
The unit for the period of a diagnostic ultrasound wave is:
Microseconds
Which of the following are appropriate to describe the period of an acoustic wave?
Minutes and microseconds
Comparing the velocity of sound in soft tissue with that in bone, the velocity of sound in bone is ____.
More than twice as fast
Is wavelength adjustable?
No
If the frequency of the beam increases, the propagation speed in the media will ____.
Not change
The unit of measurement for wave frequency is a measurement of:
Number
When you change the fundamental frequency, which of the following changes?
Numbers of cycles per second
The ____ of a sound wave refers to the time it takes to complete one cycle.
Period
The ____ of a wave is defined as the time for one wavelength.
Period
You should be familiar with the equation L=C/F. What does the "C" stand for in this equation?
Propagation speed
The formula for wavelength is:
Propagation speed / frequency
Which statement is true considering the propagation speed of sound through air?
Propagation speed in air is slower than in soft tissue
What is the relationship between power and intensity
Proportional
As a sound wave travels through soft tissue, what happens to the period of the wave?
Remains constant
What is the units for propagation speed
Seconds
Which of the following is correct regarding the wavelength of a sound wave?
Shorter wavelengths are preferred for better image resolution
As a general rule, which of these lists identify media in decreasing order of propagation speed?
Solid, liquid, gas
Which statement is accurate regarding sound propagation through a vacuum?
Sound cannot travel through a vacuum
Intensity is determined by?
Sound source
The distance that a sound wave travel through a medium in a second
Speed
Sound propagates faster in media (materials) with greater
Stiffness
Which pulse has a longer wavelength, 2 or 10MHz?
The 2 MHz pulse
Which sound has the longer period, 2 or 10MHz??
The 2 MHz pulse
The velocity of sound waves is primarily dependent on:
The media in which the sound travels
Two sound pulses travel through the same medium. One's wave's frequency is 2 MHz and the other is 10 MHz. Which pulse has the lower propagation speed?
The propagation speeds of all sound waves are identical while traveling in a specific media, regardless of frequency.
What determines the intensity of an ultrasound beam after it has traveled through the body?
The sound source and the medium at which the sound travels
Frequency of a sound wave is determined by
The source of the sound
Which pulse has the lower propagation speed?
They are the same
The definition of period of a wave cycle is
Time for one complete cycle to occur
If the power of the beam is tripled while the cross-sectional area remains the same, the intensity ____.
Triples
A songrapher can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imaging. T/F?
True
If the periods of two waves are the same, then the frequencies of the waves must also be the same. T/F?
True
With diagnostic ultrasonic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer. T/F?
True
With standard diagnostic imaging instrumentation, the sonographer has the ability to vary the amplitude of a sound wave produced by the transducer. T/F?
True
The wavelength of a cycle in an ultrasound wave can be reported with which units?
Units of distance (feet, etc)
The propagation speeds of ultrasound waves in muscle, liver, kidney and blood are____.
Very similar to each other
What is a unit of power?
Watt
Intensity is expressed in units of ____.
Watt/cm^2
The power of an ultrasound wave can be reported with which of the following units?
Watts
The units for intensity are:
Watts/cm^2
Which of the following sound wave parameters varies as the propagation speed changes in different media?
Wavelength
You should be familiar with the equation L=C/F. What does the "L" stand for in this equation?
Wavelength
Is intensity adjustable?
Yes
Terms that can be used to describe the strength of a sound beam are
amplitude and intensity
The highest speed of sound is through which body structure?
bone
