Ultrasound physics Chapter 3 review

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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


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