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Ultrasound Physics > Exam 2 > Flashcards

Exam 2 Flashcards

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1
Q

What is the range of period commonly found in waves produced by ultrasound systems?

A

.06- .5us

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2
Q

With standard ultrasonic imaging, what happens to the period of a wave as it propagates?

A

Remains the same

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3
Q

What determines the period of an ultrasound wave?

A

The transducer

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4
Q

Which of the following units are appropriate to describe the period of an acoustic wave?

Minutes 
Meters
Microseconds
Mm/us
Cubic centimeters
A

Minutes

Microseconds

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5
Q

True or false? The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.

A

False

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6
Q

What term describes the number of cycles that an acoustic variable completes in a second?

A

Frequency

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7
Q

Which of the following cannot be considered a unit of frequency?

Per day
Cycles/sec
Hz
Hertz
Cycles
A

Cycles- informs us of the number of events but not of the duration of time

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8
Q

What is the range of frequencies emitted by transducers used in ultrasonic imaging?

1 to 3 MHz

1 to 1,000 kHz

-10,000 to +10,000Hz

2,000,000 to 15,000,000 Hz

A

2,000,000 to 15,000,000 Hz

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9
Q

What establishes the frequency of an ultrasound wave?

A

The transducer

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10
Q

True or false?

With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body.

A

False

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11
Q

When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency?

A

Remains unchanged

-imaging depth and frequency are unrelated

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12
Q

Ultrasound is defined as a sound with a frequency of ___.

A

Greater than .02MHz

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13
Q

Infrasound is defined as a sound with a frequency of ___.

A

Less than 20 Hz

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14
Q

True or false?

Waves in the ultrasound range behave in the same general manner as sound waves that are audible.

A

True

-primary diff btw audible waves and ultrasonic waves is that humans can hear audible waves

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15
Q

What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz?

A

Humans can’t hear them

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16
Q

What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared with waves having frequencies of more than 20 Hz?

A

Humans can’t hear them

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17
Q

The frequency of a continuous acoustic wave is 5 MHz. The wave is then pulsed with a duty factor of 0.1. What is the new frequency?

A

Frequency is the reciprocal of the period.

5MHz

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18
Q

True or false?

The period of an ultrasound wave is related to the frequency and is the same, regardless of whether the wave is pulsed or continuous.

A

True

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19
Q

True or false?

If the periods of the two waves are the same, then the frequencies of the waves must also be the same.

A

True

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20
Q

Compare two 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

A is 3x as long as B

Frequency and period are reciprocals

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21
Q

____ is the reciprocal of period.

A

Frequency

As one increases, the other decreases
When multiplied, the result is unity

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22
Q

A wave with a period of 1/100th of a second has a frequency of ___ per second.

A

100 per second or 100Hz

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23
Q

What determines the initial amplitude of an ultrasound wave?

A

The transducer

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24
Q

True or false?

With standard diagnostic imaging instrumentation, the sonographer has the ability to vary the amplitude of a sound wave produced by the transducer.

A

True

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25
Q

As an ultrasound wave travels through the body, it’s amplitude usually:

A

Decreases

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26
Q

Which of the following are acceptable units for the amplitude of an acoustic wave?

Watts
Cm
Pascals
Gauss

A

Cm

Pascals

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27
Q

The maximum value of the density of an acoustic wave is 60 lb/in^2 while the minimum density is 20 lb/in^2. What is the amplitude of the wave?

A

Amplitude = max value of acoustic wave- min value and then divide the number in half.

60-20= 40 lb/in^2

40/2= 20 lb/in^2

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28
Q

The power of an ultrasound wave can be reported with which units?

A

Power = watts

Watts of a lightbulb, stereo system, etc

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29
Q

Typically an ultrasound wave travels through soft tissue, the power of the wave:

Decreases
Increases
Stays the same

A

Decreases

-as a sound travels through the body the power diminishes. This is called attenuation

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30
Q

True or false

A sonographer can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imaging

A

True

Power and amplitude are related
When amplitude increases, power increases

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31
Q

Mathematically, when a number is squared, the number is multiplied by ___.

A

Itself

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32
Q

The final amplitude of an acoustic wave is reduced to one-half of its original value. The final power is ___ the original power.

The same as
One- half
Double
None of the above

A

None of the above

Changes in the power of a wave are proportional to changes in the wave’s amplitude squared. One-half squared equals one-quarter (1/2 x 1/2 = 1/4). When one half of the wave’s original amplitude remains, then only one-fourth of the original power remains.

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33
Q

The amplitude of an acoustic wave decreases from 27 pascals to 9 pascals. If the initial power in the wave was 27 watts, what is the wave’s final power?

A

3 watts

One third squared equals one ninety

Thus only one-nineth of the wave’s original power remains. The original power was 27 watts

27/1 x 1/9 = 3 watts

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34
Q

The intensity of an ultrasound beam is defined as the ___ in a beam ___ by the ___ of the beam.

Power, multiplied, diameter
Amplitude, divided, area
Power, divided, area
Amplitude, multiplied, circumference

A

Power, divided, area

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35
Q

As sound travels in the body, what typically happens to the intensity of the wave?

A

Decreases

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36
Q

What are the units of intensity?

A

Watts/cm^2

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37
Q

True or false?

With diagnostic ultrasonic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer.

A

True

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38
Q

What determines the initial intensity of an ultrasound beam?

A

The source of the sound wave

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39
Q

What determines the intensity of an ultrasound beam after it has traveled through the body?

A

1) The sound wave’s source

2) The medium through which the sound travels

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40
Q

What are the units of the transmitted intensity of a sound wave?

A

W/cm^2

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41
Q

What happens when the power in an ultrasound beam is unchanged, and at the same time, the beam area doubles?

A

Is halved

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42
Q

What happens to an acoustic beam’s intensity when the power in the beam increases by 25% while the cross sectional area of the beam remains the same?

A

It increases by 25%

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43
Q

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:

A

Four times larger

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44
Q

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?

A

Increases ninefold

When the amplitude of a wave is tripled, the intensity is increased ninefold (3x3=9)

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45
Q

If the power of the beam is tripled while the cross sectional area of the beam remains the same, the intensity ____.

A

Triples

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46
Q

The amplitude of an acoustic wave ave is increased. Which of the following will most likely remain unchanged?

Power
Frequency
Period
Intensity

A

Frequency

Period

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47
Q

A sonographer adjusts the output power of the wave emitted by the transducer. Which of the following also changes?

Pulse repetition period
PRF
Propagation speed
Intensity

A

Intensity

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48
Q

The wavelength of a cycle in an ultrasound wave can be reported with which units?

A

Units of distance (feet, etc.)

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49
Q

The wavelength of an ultrasonic wave is determined by:

A

1) the sound source

2) the medium through which the wave travels

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50
Q

What is the wavelength of 2 MHz sound in soft tissue?

A

Wavelength (mm) = 1.54/ frequency (MHz)

For 2 MHz sound, the wavelength is 1.54/2 or .77MHz

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51
Q

Which of the following terms best describes the relationship btw frequency and wavelength for sound traveling in soft tissue?

A

Inverse

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52
Q

Two sound pulses travel through the same medium. One wave’s frequency is 2 MHz and the other is 10 MHz.

Which sound wave has a longer period?

A

The 2 MHz pulse has a period five times longer than the 10 MHz wave

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53
Q

Two sound pulses travel through the same medium. One wave’s frequency is 2 MHz and the other is 10 MHz.

Which pulse has a longer wavelength?

A

The 2 MHz pulse

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54
Q

Two sound pulses travel through the same medium. One wave’s frequency is 2 MHz and the other is 10 MHz.

Which pulse has the lowest power?

A

Cannot be determined

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55
Q

Two sound pulses travel through the same medium. One wave’s frequency is 2 MHz and the other is 10 MHz.

Which pulse has a longer spatial pulse length?

A

Cannot be determined

56
Q

True or false

Lower frequency sound creates higher quality images with greater detail.

A

False

57
Q

What is the wavelength of 10MHz sound in soft tissue?

A

1.54/10 or .15mm

Wavelength = 1.54/ frequency

58
Q

Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?

The period of 5 MHz wave is less than the period of the audible wave.

A

True

59
Q

Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?

The wavelength of the 5MHz wave is greater than the wavelength of the 5kHz wave.

A

False

60
Q

Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?

The ultrasound wave travels much faster than the audible wave.

A

False

All sound waves travel the same speed regardless of frequency

In soft tissue, speed propagates at a peed of 1,540 m/sec

61
Q

Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?

Both the 5MHz and the 5 kHz waves travel at similar speeds through the medium.

A

True

62
Q

An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?

The frequency of the wave increases as it travels through the mass.

A

False

63
Q

An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?

The period of the sound wave decreases as it travels through the mass.

A

False

64
Q

An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?

The wavelength increases while the wave travels through the mass.

A

True

65
Q

An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?

The power in the wave increases as it travels through the mass.

A

False

66
Q

Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?

The waves travel through all three media at the same speed since they have identical frequencies.

A

False

67
Q

Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?

The sound waves travel through all three media at different speeds because the waves have different powers.

A

False

68
Q

Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?

The waves travel through all three media at different speeds bc the waves have different powers.

A

False

69
Q

Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?

The waves travel through all three media at different speeds bc the media are different.

A

True

70
Q

Propagation speed can be correctly recorded with which of the following units?

Miles per hour
Mm/sec
Km/sec
Inches per year

A

All of the above

71
Q

The propagation speed of continuous wave ultrasound is 1.8 kilometer per second. The wave is then pulsed with a duty factor of 50%. What is the new propagation speed?

A
  1. 8 km/sec
    - there is no difference in sound’s speed whether the wave is continuous or pulsed. The new and old speeds will be identical
72
Q

What is the best estimate of the distance that sound can travel in soft tissue in one second?

A

1,540 meters per second in soft tissue. This is approximately one mile per second.

73
Q

True or false?

Shorter wavelength sound creates higher quality images with greater detail.

A

True

74
Q

True or false?

The wavelength of an acoustic wave is shorter when it is pulsed rather than continuous.

A

False

Wavelength doesn’t change based on whether cycle is pulsed or continuous

75
Q

The speed of sound traveling through bone is ___ soft tissue.

Lower than
Higher than
Equal to
Cannot be determined

A

Higher than

76
Q

Compared to soft tissue, the speed of an acoustic wave through lung tissue is ___.

A

Slower

-speed of sound in lung tissue is slower than in soft tissue.

77
Q

What is the best estimator the speed of sound in tendon?

1,000 m/s
1,540 m/s
1,754 m/s
5,400 m/s

A

1,754 m/s

Sound travels slightly faster in tendon than in soft tissue.

78
Q

As a general rule, which of the following lists media in increasing order of propagation speeds?

Gas, solid, liquid
Liquid, solid, gas
Solid, liquid, gas
Gas, liquid, solid

A

Gas, liquid, solid

Generally sound travels slowest in gases, faster in liquids, and fastest in solids

79
Q

What is the speed of sound in air?

A

330 m/s

80
Q

True or false?

Soft tissue is an imaginary construct that actually does not exist.

A

True

Soft tissue is an imaginary structure with characteristics that represent an “avg” of body tissues such as muscle, blood, kidney, and spleen. It is used as an approximation.

81
Q

What is the propagation speed of a 5 MHz (megahertz) sound wave in soft tissue?

A

1.54 mm/us
1,540 m/sec
1.54 km/sec

82
Q

If sound doesn’t travel at 1,540 m/sec in a medium, then the medium ___.

A

Cannot be soft tissue

83
Q

If sound travels at exactly 1,540 m/sec in a particular medium, then the medium ___.

A

May be soft tissue

84
Q

The propagation speeds of ultrasound waves in muscle, liver, kidney, and blood are ___.

A

Very similar to each other

85
Q

The speed at which a wave travels through a medium is determined by:

A

The characteristics of the medium only

86
Q

What two properties establish sound’s propagation speed in a given medium

A

Density and stiffness

87
Q

The characteristics of four media are described below. Which of the media has the slowest propagation speed?

A

High density and high elasticity

88
Q

Compressibility describes a characteristic of a medium. Which two terms describe the same property as compressibility?

A

Stiffness and elasticity

89
Q

When the elasticity of a medium is high, the ___ is high.

A

Compressibility

90
Q

Two sound waves with frequencies of 5 and 3 MHz travel to a depth of 8 cm in a medium and then reflect back to the surface of the body. Which acoustic wave arrives first at the surface of the body?

A

Neither

Both travel at the same speed and reach body at the same time- frequency is irrelevant to speed

91
Q

What are the units of pulse duration?

A

Units of time (sec, min, years, etc)

.3 to 2 usec

92
Q

What determines the pulse duration?

A

The source of the wave

Pulse duration- the actual time that a transducer is creating one sound pulse and is determined by the ultrasound system. Pulse duration does not include the listening time.

93
Q

True or false?

The pulse duration of an ultrasound and transducer system does not change significantly as long as the system components remain unchanged.

A

True

94
Q

The pulse duration is expressed in the same units as ___.

A

Period

95
Q

True or False?

A sonographer can adjust the duration of an acoustic pulse since it depends upon the pulse’s propagation speed.

A

False

96
Q

True or False?

A sonographer can adjust the duration of an acoustic pulse since it depends upon the maximum imaging depth.

A

False

Pulse duration has a constant value and can’t be changed nor is it dependent on imaging depth

97
Q

True or False?

The pulse duration cannot be changed under any circumstances or by any action of the sonographer.

A

False

It can be altered by switching to a different imaging transducer

98
Q

True or False?

The sonographer cannot change the duration of a sound pulse unless the transducers are switched.

A

True

99
Q

What is the pulse duration equal to?

A

Period multiplied by the number of cycles in the pulse

100
Q

What happens to the pulse duration when a sonographer decreases the maximum imaging depth in an ultrasound scan?

A

Remains the same

The time that a transducer is “pulsing” does not change with alterations in depth of view

101
Q

The spatial pulse length describes certain characteristics of an ultrasound pulse. What are its units?

A

Meters

102
Q

In diagnostic imaging, what determines the spatial pulse length?

A

1) The ultrasound system

2) the medium through which the pulse travels

103
Q

Which of the following best describes the spatial pulse length?

Frequency multiplied by wavelength

PRF multiplied by wavelength

Wavelength multiplied by the number of cycles in the pulse

Duty factor multiplied by the wavelength

A

Wavelength multiplied by the number of cycles in the pulse

104
Q

Two transducers send ultrasound pulses into soft tissue. One transducer emits sound with a 4MHz frequency, and the other produces sound at 6MHz frequency. Each pulse contains 4 cycles. Which has a greater spatial pulse length?

A

The 4MHz pulse

4MHz wave has a longer wavelength than the 6MHz wave and therefore will have a longer spatial pulse length.

105
Q

Using a specific transducer, what happens to the spatial pulse length as the sonographer increases the maximum imaging depth?

A

Remains the same

106
Q

True or false?

While imaging soft tissue, the spatial pulse length does not change as long as the components of the ultrasound system are the same.

A

True

107
Q

On what does the pulse repetition period depend?

A

The source of the sound wave

108
Q

A sonographer adjusts the maximum imaging depth of an ultrasound system. Which of the following also changes?

A

Pulse repetition period

Pulse repetition frequency

109
Q

Which of the following correctly describes pulse repetition period?

A

The sum of the pulse’s “on” time and the listening “off” time

110
Q

What happens to the pulse repetition period if the sonographer decreases the maximum imaging depth achieved in an ultrasound scan?

A

Decreases

111
Q

Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?

The period of the 3MHz sound is greater than the period of the 6 MHz sound.

A

True

112
Q

Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?

The wavelength of the 3MHz ultrasound is greater than the 6MHz sound.

A

True

113
Q

Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?

The pulse produced by both systems travel at the same speed in the patient.

A

True

114
Q

Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?

The PRF of the 6 MHz transducer is greater than the PRF of the 3 MHz transducer.

A

False

The PRF changes only when imaging depth changes. Since the depth of view for both systems is the same, the PRFs are also the same.

115
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?

The pulse repetition period is increased.

A

False

116
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?

The pulse repetition frequency is increased.

A

False

117
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?

The duty factor is increased.

A

True

118
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?

The frequency is increased.

A

False

119
Q

What are the units of pulse repetition frequency (PRF)?

A

1/seconds

PRF has the same units as frequency, and these units are Hz or per second

120
Q

The pulse repetition frequency of ultrasound produced by a transducer typical of diagnostic imaging systems ___.

A

Can be changed by the changed by the sonographer

Sonographers alter PRF when they adjust imaging depth. As depth increases, PRF must decrease. This occurs bc transducer must wait a longer time for echoes to return from deeper depths.

121
Q

I’m diagnostic imaging, what establishes the pulse repetition frequency?

A

The source of the sound/acoustic wave

Medium through which sound travels does not directly affect PRF

122
Q

When a sonographer increases the maximum imaging depth during an exam, what happens to the PRF?

A

PRF decreases

123
Q

True or False?

The PRF and frequency are unrelated.

A

True

  • PRF is only determined by depth
  • Frequency is determined by characteristics of transducer
124
Q

The pulse repetition frequency is the ___.

A

Reciprocal of pulse repetition period

If PRF is 100 per second, then PRP is one-one hundredth of a second (.01)

125
Q

What is the typical value for the duty factor/ duty cycle of pulsed sound waves used in diagnostic imaging?

A

.001

126
Q

What is the value of the duty cycle for continuous wave ultrasound?

A
  1. 0 or 100%

- this means the transducer is producing an acoustic signal at all times

127
Q

In the case of pulsed ultrasound, what is the maximum value of the duty factor?

A

Less than 100%

-this is bc at least a tiny bit of time must be spent listening rather than transmitting the wave. Therefore, the percentage of time transmitting must be less than 1 or less than 100%.

If the percentage equals 100%, then the system is a continuous wave.

128
Q

While using a particular imaging system, what happens to the duty factor when the depth of view increases?

A

Decreases

Duty factor and depth are inversely related

129
Q

True or False?

The sonographer alters the duty cycle when adjusting the maximum imaging depth of a scan.

A

True

Duty factor and depth are inversely related

-depth increases, duty factor decreases

130
Q

True or false?

The duty factor is a characteristic of an ultrasound and transducer system and does not change as long as the system components remain unchanged.

A

False.

Duty cycle changes when depth changes during an exam

131
Q

While using the same ultrasound machine and transducer, which of the following can a sonographer alter?

Pulse repetition period

Pulse repetition frequency

Frequency

Duty cycle

Pulse duration

A

PRP
PRF
Duty cycle

132
Q

Which of the following terms does not belong with the others?

Increased depth of view
Increased duty factor
Increased pulse repetition period
Decreases pulsed repetition frequency

A

Increased duty factors are related to shallower imaging

The other three are consistent with deeper imaging

133
Q

Which of the following terms does not belong with the others?

Increased depth of view
Decreases duty factor
Increased pulse repetition period
Decreased spatial pulse length

A

Decreased spatial pulse length is unrelated to alterations in depth of view imaging

The other three are all related to deeper imaging

134
Q

What is the importance of describing sound beam intensities in a variety of ways with regard to space and time?

A

It’s important when studying bioeffects

Describing the intensity of a sound beam as they vary in time and space is important in the study of bioeffects

135
Q

Which intensity is most closely correlated to tissue heating?

SPTP
SATP
SPTA
SATA

A

The SPTA intensity relates most closely to the tissue temperature elevation.

Ultrasound Physics (6 decks)

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