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Ultrasound Physics > Exam 1 Study Questions > Flashcards

Exam 1 Study Questions Flashcards

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1
Q

What is time per cycle?

A

Period

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2
Q

What is it called when there is a large, smooth interface?

A

Specular reflection

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3
Q

What is the maximum variation per cycle?

A

Amplitude

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4
Q

Less than 20 Hz

A

Infrasound

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5
Q

What is length per cycle?

A

Wavelength

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6
Q

What is cycles per second?

A

Frequency

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7
Q

What is the speed of a wave through a medium?

A

Propagation speed

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8
Q

When the structure’s dimensions are much smaller than the beams wavelength (red blood cells)

A

Rayleigh scattering

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9
Q

When the incident sound beam strikes the boundary at exactly 90 degrees

A

Normal incidence

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10
Q

Backscatter

A

Diffuse reflection

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11
Q

Define axial resolution

A

The ability to clearly define two separate reflectors that are very close together and parallel to the sound beam

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12
Q

List 3 of the acoustic parameters and their applicable units

A

Period
Frequency
Amplitude
Power
Intensity
Wavelength
Propagation speed

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13
Q

Define constructive interference

A

A pair of in-phase waves results in the formation of a single wave of greater amplitude

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14
Q

Define destructive interference

A

A pair of out-of-phase waves results in the formation of a single wave of lesser amplitude

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15
Q

Define specular reflection

A

A sound wave is reflected off of a smooth, flat surface and in one direction

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16
Q

Define diffuse reflection

A

A sound wave is reflected off a rough, uneven surface in multiple directions (backscatter)

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17
Q

Define half-value layer/half-value thickness

A

The distance sound travels in a tissue that reduces the intensity of sound to one-half its original value.

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18
Q

If system A has a wavelength of 5mm for a two-cycle pulse and system B has a wavelength of 2mm for a two-cycle pulse, which one is going to provide the best axial resolution?

A

System B

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19
Q

Define impedance

A

Acoustic resistance to sound traveling in a medium

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20
Q

What is the formula for impedance?

A

Impedance = density x propagation speed
z=c(p)

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21
Q

If the intensity at the start of the path is 10 mW/cm2 and the attenuation over the path is 6dB, the intensity at the end of the path is _____ mW/cm2

A

-6 = ¼ (10 x ¼) = 2.5 mW/cm2

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22
Q

If the intensity at point A is 20 mW/cm and at point B it is 10 mW/cm, the attenuation from A to B is _____ dB.

A

-3 dB

-3 = ½ 20 x ½ = 10

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23
Q

If the incident angle is 40 degrees and the transmission angle is 30 degrees, what is the change is speed from Medium 1 to Medium 2 ____

A

Decreases

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24
Q

Propagation speed increases if stiffness ____

A

Increases

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25
Q

If power is doubled and area remains the same, intensity ____

A

Increases

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26
Q

Destructive interference results in a wave where the amplitude ____

A

Decrease

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27
Q

As a wave travels through a medium, the intensity of the wave ____

A

Increases

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28
Q
  1. Frequency decreases as period ____
A

Increases

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29
Q

If the frequency is increased, the attenuation ____

A

Increases

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30
Q

If the wavelength increases, frequency ____

A

Decreases

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31
Q

The depth is changed from 6 cm to 12 cm, the pulse repetition frequency ____

A

Decreases

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32
Q
  1. How many mm are in 8 km
A

8,000,000

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33
Q

Which is adjustable by the sonographer?

A

Amplitude

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34
Q

Refraction occurs when ____

A

An interface is encountered at oblique incidence with different propagation speeds

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35
Q

Which of the sequences of metric abbreviations are in increasing order?

A

u, m, c, d, M

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36
Q

Spatial pulse length is determined by:

A

Both the sound source and medium

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37
Q

If the frequency is doubled, the wavelength is:

A

Halved

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38
Q

What is a unit for intensity?

A

mW/cm^2

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39
Q

How are pulse repetition period and depth related?

A

Directly

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40
Q

A wave is non-perpendicular at an interface. The propagation speed of medium 1 is higher than medium 2. The transmitted wave will have an angle that _______ the incident angle

A

Is less than

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41
Q

What determines attenuation?

A

Path length and frequency

42
Q

How are cholesterol level and life span related?

A

Inversely

43
Q

What is the fraction of time that ultrasound is emitted?

A

Duty factor

44
Q

Which one of the following contributes the most to attenuation?

A

Absorption

45
Q

_____ is measured in Rayls

A

Impedance

46
Q

The horizontal axis on a graph is the _______ axis.

A

x-axis

47
Q

Convert 12 inches to centimeters (2.54 cm = 1 inch)

A

30.48 cm

48
Q

What is 1,300,000 in scientific notation?

A

1.3x10^6

49
Q

What is 0.000000351 in scientific notation?

A

3.51x10^-7

50
Q

All sound waves carry __________ from one location to another.

A

Energy

51
Q

What type of wave is a sound wave?

A

Longitudinal

52
Q

What is the definition of density?

A

Concentration of mass in a volume

53
Q

Acoustic parameters include:

A

Period, frequency, amplitude, power, intensity, wavelength, and propagation speed

54
Q

A _________ is a collection of cycles that travel together.

A

Pulse

55
Q

________ are desirable for imaging because they create images with better axial resolution.

A

Shorter pulses

56
Q

What determines axial resolution?

A

Spatial resolution

57
Q

A cycle includes ________.

A

One positive half wave and one negative half wave

58
Q

Used to help focus the beam

A

Lens

59
Q

Converts electrical to mechanical energy

A

Piezoelectric materials

60
Q

Lowers the acoustic impedance mismatch between the transducer and the patient

A

matching layer

61
Q

Delivers the drive voltage to the crystal and echo voltage to the recievers

A

Wires

62
Q

Dampening component

A

Backing material

63
Q

The ability to distinguish between two structures

A

Resolution

64
Q

The operating or main frequency

A

Resonant frequency

65
Q

Where the beam reaches its minimal diameter

A

Focus

66
Q

Fresnal

A

Near field zone

67
Q

Fraunhofer

A

Far field zone

68
Q

True or false: damping lengthens the pulse

A

False

69
Q

True or false: PZT stands for lead zirconate titanate

A

True

70
Q

In the near zone beam width ____ as distance from the transducer increases.

A

Decreases

71
Q

Doubling the aperture ____ the near zone length.

A

Increases

72
Q

A higher-frequency transducer produces more or less divergence in the far field?

A

Less

73
Q

True or false: in pulse-echo system, the desired Q factor is an large as possible

A

False

74
Q

True or false: the beam diameter is constant in the near zone

A

False

75
Q

Divergence of a sound beam of an unfocused transducer occurs in the ____ zone

A

Fraunhofer

76
Q

In a sound wave, regions where the pressure is higher than normal are called regions of ____.

A

Compression

77
Q

Bandwidth can be increased by increasing ____.

A

Damping

78
Q

What is the depth of the object if the go-return time is 7 us?

A

1.54 x 7 / 2 = 5.39 mm

79
Q

At what part of the beam is the intensity the greatest?

A

At the focus

80
Q

What is the name given to describe electronic focusing of multi-element transducers?

A

Phasing

81
Q

According to the range equation, which of the following are necessary to calculate the distance to the reflector?

A

Propagation speed and go-return time.

82
Q

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

A

It decreses

83
Q

The reverse piezoelectric effect describes the ____ of a sound wave.

A

Transmission

84
Q

The thickness of the element is equal to ____ the wavelength of the resonate frequency.

A

1/2

85
Q

Reflection of the sound beam from a large interface with a rough surface is called ____.

A

Diffuse reflection

86
Q

The optimal impedance of the matching layer would be about ____ rayls if the element is 25 rayls and tissue is 3.5 rayls.

A

15 rayls

87
Q

The optimal thickness of the matching layer is ____ of the wavelength of resonant frequency.

A

25%

88
Q

For modern day ultrasound scanners, the most favorable resolution factor is ____.

A

Axial

89
Q

The size of the focus of a 2 MHz, 8mm diameter single element unfocused transducer is ____

A

4 mm

90
Q

The most commonly used material in modern transducer elements is ____.

A

Lead zirconate titanate

91
Q

What determines the PRF of a sound wave?

A

Imaging depth

92
Q

Backing material improves____ axial resolution.

A

Improves

93
Q

Heating a transducer above the ____ ____ will cause depolarization.

A

Curie point

94
Q

Two ultrasound systems have near zone lengths of 8cm. At the focus System G has a lateral resolution of 3.0mm, whereas System p has a lateral resolution of 5.0mm. Which system is more likely to produce higher quality pictures at the focus?

A

System G

95
Q

Slice thickness can be improved by ____.

A

Curving the element or using a lens

96
Q

Which of the following transducers would give the shallowest focus?

A

Diameter = 1mm; Frequency = 2 MHz (smaller diameter and lower frequency)

97
Q

What is the most common form of fixed focusing?

A

Internal

98
Q

The range equation relates ____, ____, and ____.

A

Distance, velocity, and time.

99
Q

Two crystals of the same thickness are used for transducers A and B. The propagation velocity on transducer A’s crystal is twice that of transducer B. Which means transducer ____ operates at ____ the operating frequency.

A

A; twice

100
Q

Which quantity is unitless?

A

Q-factor

101
Q

The Q value of a transducer is determined by ____.

A

Bandwidth

102
Q

What can be used to focus an ultrasound beam?

A

Curved crystal, acoustic lens, and phasing.

Ultrasound Physics (11 decks)

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