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Ultrasound Physics > Midterm Review > Flashcards

Midterm Review Flashcards

1
Q

Interfaces that scatter ultrasound energy are usually considered to be those that are equal to or smaller than ________.

A

Wavelength

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2
Q

Interfaces that scatter ultrasound energy are usually considered to be those that are _______ or _______wavelength.

A

Equal to

Smaller than

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3
Q

Regions of lower pressure and density are called ______.

A

Rarefactions

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4
Q

Define rarefactions

A

Regions of lower pressure and density

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5
Q

If you switch to a lower frequency for penetration, the wavelength of the transducer will ________.

A

Increase

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6
Q

Frequency and wavelength are _______ related.

A

Inversely

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7
Q

The attenuation of a 5.0 MHz transducer at a depth of 4 cm is _____.

A

10 dB

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8
Q

What is the formula for attenuation?

A

Total attenuation= attenuation coefficient X depth

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9
Q

What is the formula for attenuation coefficient?

A

Attenuation coefficient= Frequency/2

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10
Q

T or F. The higher the transducer frequency, the higher the Rayleigh scattering.

A

True

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11
Q

Transducer frequency and Rayleigh scattering are ________ related.

A

Directly

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12
Q

T or F. 15 kHz is not a ultrasound frequency.

A

True

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13
Q

The duty factor will increase with:

A

PRP
Pulse duration
Period

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14
Q

The attenuation of a 5 MHz transducer in soft tissue would be ____ dB at 2 cm of depth.

A

5

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15
Q

_____ microsec is the period of a 5.0 MHz transducer in soft tissue.

A

0.2

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16
Q

What is the formula for impedance?

A

Impedance= Density X propagation speed

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17
Q

Density X propagation speed=

A

Impedance

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18
Q

Continuous wave doppler has a duty factor of ______.

A

100%

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19
Q

What has a duty factor of 100% ?

A

Continuous wave doppler

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20
Q

For perpendicular incidence, the incidence angle is ______.

A

90 degrees

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21
Q

The incidence angle is 90 degrees for __________.

A

Perpendicular incidence

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22
Q

T or F. Attenuation decreases with an increase in wavelength.

A

True

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23
Q

Attenuation and wavelength are ________ related.

A

Inversely

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24
Q

The average propagation speed in human soft tissue is ________.

A

1.54 mm/microsec

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25
Q

1.54 mm/microsec is the average propagation speed in ___________.

A

Human soft tissue

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26
Q

Frequency is _______ related to wavelength.

A

Inversely

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27
Q

The distance to a reflector in soft tissue is 15 cm. __________ is the round trip to this depth.

A

195 microseconds

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28
Q

The time it takes for one cycle to occur is _______.

A

Period

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29
Q

What is period?

A

The time it takes for one cycle to occur

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30
Q

In __________ the sound is refracted at a boundary between two media where propagation speeds are different.

A

Oblique incidence

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31
Q

In oblique incidence the sound is refracted at a boundary between two media where propagation speeds are ________.

A

different

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32
Q

_________ relates the transmitted beam direction to the incidence beam direction and the speeds of sound in the two materials forming the interface.

A

Snell’s law

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33
Q

The number of pulses that occur in a second is called ______.

A

Pulse repetition frequency

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34
Q

When frequency increases, the period ________.

A

Decreases

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35
Q

The maximum variation that occurs in an acoustic variable is called ___________.

A

Amplitude

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36
Q

Amplitude is _________________________.

A

The maximum variation that occurs in an acoustic variable .

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37
Q

-3 dB of attenuation mean _________ the original intensity.

A

One-half

Choose best answer on test: Possibly 3dB

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38
Q

If beam power increases, intensity will __________.

A

Increase

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39
Q

Beam power and intensity are _______ related.

A

Directly

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40
Q

The speed at which a wave travels through a medium is called _________.

A

Propagation speed

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41
Q

Define propagation speed.

A

The speed at which a wave travels through a medium.

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42
Q

Sound is a _________ wave.

A

mechanical longitudinal

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43
Q

The wavelength of 3 MHz ultrasound in soft tissue is _____.

A

0.51 mm

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44
Q

________ sound is NOT described by pulse duration.

A

Continuous wave

45
Q

T or F. Continuous wave (CW) is described by pulse duration.

46
Q

The number of complete cycles per second is called ________.

47
Q

Define frequency.

A

The number of complete cycles per second

48
Q

As sound travels, the reduction in amplitude and intensity of the wave is called ________.

A

Attenuation

49
Q

Define attenuation.

A

The reduction in amplitude and intensity of the wave as sound travels.

50
Q

T or F. The propagation speed is higher in bone than soft tissue.

51
Q

Is propagation speed higher in soft tissue or bone?

52
Q

Sound requires ___________.

A

a medium through which to travel.

53
Q

Ultrasound pulses contain a range of frequencies called ___________.

54
Q

What is bandwidth?

A

Ultrasound pulses with a range of frequencies.

55
Q

Does duty factor have a unit?

56
Q

T or F. Duty factor is unitless.

57
Q

T or F. The spatial pulse length does not increase with frequency

58
Q

Spatial pulse length and frequency are _________.

59
Q 
The propagation speed for a round trip time of 39 microseconds is \_\_\_\_\_\_\_ mm/microsecond.
1540.0
15.4
1.45
NONE OF THE ABOVE
A

NONE OF THE ABOVE

60
Q

Examples of acoustic parameters:

A

Cycle
Period
Frequency

61
Q

Cycle, period, and frequency are examples of ___________.

A

Acoustic parameters

62
Q

The fraction of time that pulsed ultrasound is on is called _____________.

A

Duty factor

63
Q

What is duty factor?

A

The fraction of time that pulsed ultrasound is on

64
Q

Pulse repetition frequency is the number of pulses occurring in ___ second.

65
Q

The number of pulses occurring in 1 second is _________

A

Pulse repetition frequency

66
Q

What is pulse repetition frequency?

A

The number of pulses occurring in 1 second

67
Q

T or F. Attenuation is higher in bone than in soft tissue.

68
Q

Is attenuation higher is soft tissue or bone?

69
Q

Is compression an acoustic variable?

70
Q

_________ is not an acoustic variable.

A

Compression

71
Q

What are the acoustic vatiables?

A

Pressure
Density
Distance

72
Q

The best way to describe the role of ultrasound scattering in diagnostic imaging is that ________________________.

A

It allows us to see the tissue interfaces

73
Q

The distance to the reflector in soft tissue with a round-trip time of 39 microseconds is _______.

A

30 mm or 3 cm
because
1 cm=10mm

74
Q

If the beam area decreases, the intensity will _______.

75
Q

Beam area and Intensity are ______ related.

76
Q

The four intensity values from the greatest to the least are:

A

SPTP
SATP
SPTA
SATA

77
Q

Heat production depends most directly on the ______________.

A

temporal average (TA) intensities.

78
Q

__________ depends most directly on the temporal average (TA) intensities.

A

Heat production

79
Q

Continuous wave ultrasound is described by:

A

Frequency
Wavelength
Propagation speed

80
Q

The rate at which energy passes through a unit area is called _______.

81
Q

Define intensity.

A

The rate at which energy passes through a unit area

82
Q

If the density of medium 2 is 10% greater than that of medium 1 and the propagation speeds are equal. The impedance of medium 2 is _____% higher for medium 1.

83
Q

Propagation speed is primarily determined by ___________.

A

The stiffness of the medium

84
Q

________ is primarily determined by the stiffness of the medium.

A

Propagation speed

85
Q

What is the units for impedance?

86
Q

Rayls is the unit for _______.

87
Q

In oblique incidence, the incidence and reflection angles are always ______.

88
Q

In __________, the incidence and reflection angles are always equal.

A

Oblique incidence

89
Q

If frequency increases, period will ________.

90
Q

Frequency and period is ________ related.

91
Q

Stiffer media have ______ sound speeds.

92
Q

T of F. Intensity is equal to the power of a wave divided by the area over which the power is spread.

93
Q

Intensity is equal to the __________ divided by the ____________.

A

Power of a wave

Area over which the power is spread.

94
Q

20kHz is equal to _________.

95
Q

500 Hz is equal to

96
Q

T of F. Stiffer media have higher sound speeds.

97
Q

______ media have higher sound speeds.

98
Q

The ____ of the media determine how much of the incident sound wave is reflected and transmitted into the ________.

A

Impedances

Second media

99
Q

The impedances of the media determine how much of the ___________ is reflected and transmitted into the second media.

A

Incident sound wave

100
Q

Attenuation encompasses:

A

Absorption
Scattering
Reflection

101
Q

Is spatial pulse length determined by the length of the pulse and the propagation speed?

102
Q

Impedance increases when ______ and __________ increases.

A

Density

Propagation speed

103
Q

Impedance, density, and propagation speed are ________ related.

104
Q

Will pulse duration increase with frequency?

105
Q

T or F. Pulse duration will increase with frequency.

106
Q

Can sound travel through a vacuum?

107
Q

Can sound travel through air, lung, and bone?

108
Q

Spatial pulse length is determined by ________.

A

Wavelength

Ultrasound Physics (30 decks)

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