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Phys Agents > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

Is US audible to the human ear

A

No

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2
Q

How is US generated

A

High frequency electrical generator that is part of an oscillatory circuit which puts energy through a crystal causing it to vibrate emitting sound waves

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3
Q

What is the crystal made of and it’s thickness

A

Synthetic ceramic 2-3 mm

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4
Q

What does the crystal convert electrical energy to

A

Mechanical acoustic energy

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5
Q

True or False:

US creates a reverse piezoelectric effect

A

True

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6
Q

What is the reverse piezoelectric effect

A

Voltage creating a mechanical compression to the crystal

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7
Q

What is the soundhead made of (3)

A

Ceramic, aluminum, or stainless steel plate

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8
Q

Is the soundhead interchangeable and why or why not

A

No because it generally matches the frequency of the crystal

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9
Q

What does the applicator house (2)

A
  1. Crystal

2. Soundhead

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10
Q

What is the applicator made out of

A

Hard insulated plastic

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11
Q

What type of wave do photons move along the wave

A

Electromagnetic

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12
Q

What type of wave do molecules bump into their neighbor resulting in propagation of energy

A

Mechanical

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13
Q

What are the 2 types of therapeutic ultrasound waves

A
  1. Longitudinal waves

2. Transverse waves

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14
Q

Can sound waves travel through a vacuum why or why not

A

No because they need to be able to bump into something

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15
Q

True or False:

US creates a wave that goes positive and negative

A

True

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16
Q

What wave type do the molecules move in the direction the wave travels and perpendicular to the direction the wave travels

A

Transverse waves

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17
Q

What wave type do molecules move along the direction the wave travels

A

Longitudinal waves

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18
Q

What is the molecular flow occurring in the same direction as the wave known as

A

Microstreaming

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19
Q

What is the near field

A

Area of the US beam closest to transducer

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20
Q

What is another name for the near field

A

Fresnel zone

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21
Q

What is the far field

A

Area of the US beam where wave begins to diverge

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22
Q

What is another name for the far field

A

Fraunhofer zone

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23
Q

What does the near field look like

A

Sound waves are transmitted in a straight line

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24
Q

What does the far field look like

A

Sound wave begins to diverge or scatter

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25
Q

What are rarefactions

A

Dispersion of molecules

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26
Q

When do rarefactions occur during US

A

The peak of the wave

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27
Q

When does compression occur during US

A

The valley of the wave

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28
Q

What is power

A

Amount of energy per unit of time

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29
Q

1W equals what

A

1 joule/sec

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30
Q

What is 1 joule equal to

A

The energy expended in 1 second by an electric current of 1 ampere in a resistance of 1 ohm

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31
Q

What is a joule equal to in foot pounds

A

0.738 foot pounds

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32
Q

What is the effective radiating area (ERA)

A

The size of the area of the transducer that radiates the US beam

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33
Q

What is the ERA dependent on

A

The size of the crystal

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34
Q

Is the ERA generally larger or smaller than the size of the transducer cover

A

Smaller

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35
Q

What is the ERA measured in

A

cm2

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36
Q

What are the 2 variables that pertain to intensity of US

A
  1. Spatial

2. Temporal

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37
Q

What is spatial intensity variable

A

Relates to the size of transducer ERA

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38
Q

What is temporal intensity variable

A

Relates to time transducer is on

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39
Q

How do you determine the spatial average intensity

A

Power/ERA

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40
Q

What is spatial peak intensity

A

The peak intensity of the US beam over the area of the transducer

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41
Q

Where is the spatial peak intensity the greatest

A

The center of the US beam

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42
Q

How do you determine the spatial average temporal average (SATA) intensity

A

Spatial average temporal peak (SATP) * Duty cycle

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43
Q

What does SATA measure

A

The amount of energy delivered to tissue

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44
Q

What is beam nonuniformity ratio (BNR) technical terms

A

Ratio of spatial peak intensity to spatial average intensity

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45
Q

What is beam nonuniformity ratio (BNR) dumby terms

A

Ratio of the intensity of the highest peak to that of the average of all peaks

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46
Q

What does a lower BNR mean

A

There is a lower probability that the patient will feel any undesirable hot spots

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47
Q

What is the recommended range for BNR values

A

2:1 and 8:1

48
Q

What is the duty cycle

A

The percent of time the US beam is on

49
Q

What does a continuous duty cycle mean

A

The US beam is always on

50
Q

What does a pulsed duty cycle mean

A

The US beam is on 10%, 20%, or 50% of the time

51
Q

What duty cycle should be used for the acute phase of healing

A

Pulse

52
Q

What duty cycle should be used for the subacute phase of healing

A

Continuous

53
Q

What duty cycle should be used for the chronic phase of healing

A

Continuous

54
Q

What does the pulse duty cycle do

A

Limits the amount of energy put in the patient

55
Q

What is the frequency equivalent to for US

A

The number of compression-rarefaction cycles per unit of time

56
Q

What is the frequency range for TUS

A

0.75 MHz to 3.3 MHz

57
Q

How deep does 1 MHz US penetrate

A

Up to 5 cm

58
Q

How deep does 3 MHz US penetrate

A

1-2 cm

59
Q

True or False:

Absorption decreases as frequency increases

A

False

60
Q

How much quicker does absorption occur for 3 MHz US compared to 1 MHz US

A

1/3 the time

61
Q

What is absorption considered

A

Conversion of mechanical energy of US wave into kinetic or heat energy

62
Q

What types of tissues absorb US the best

A

Tissues high in collagen

63
Q

What is reflection

A

Redirection of the US beam away from the surface

64
Q

How much does the soft tissue bone interface reflect US

A

35%

65
Q

How much does the skin air interface reflect US

A

100%

66
Q

How much does the skin air interface reflect US with a couplant

A

0.1%

67
Q

What is refraction

A

Wave enters tissue at one angle and continues through at another angle

68
Q

What does attenuation measure

A

The decrease in US intensity as the wave travels through tissues

69
Q

What causes the intensity of US to decrease (2)

A
  1. Absorption of US wave by tissue

2. Dispersion of US wave due to reflection and refraction

70
Q

What types of tissues have higher attenuation coefficients

A

Tissues with higher collagen content

71
Q

True or False:

Penetration and absorption of the US beam are inversely proportional to one another

A

True

72
Q

What happens to absorption as frequency increases

A

Absorption increases

73
Q

True or False:
Reflected US waves interact with the wave moving in the opposite direction potentially making the wave more intense if both waves are in phase

A

True

74
Q

How do you minimize standing waves

A

Keep the sound head moving

75
Q

What is cavitation

A

Formation, growth, and pulsation of bubbles exposed to US beam

76
Q

What is the compression phase

A

The bubbles compress

77
Q

What is the rarefaction phase

A

The bubbles expand

78
Q

True or False:

Cavitation can be stable or unstable

A

True

79
Q

True or False:

Stable cavitation is thought to produce a thermal effect of US

A

False

80
Q

Does true unstable cavitation occur at the therapeutic level

A

NOOOOOO!!!!!!!

81
Q

What is microstreaming

A

The minute unidirectional flow of fluid in the vicinity of pulsating bubbles

82
Q

What is microstreaming a result of

A

Pressure of the sound wave that moves ions or small molecules

83
Q

True or False:

The US waves that bounce off of bone can great a double heating effect to tissues between the bone and applicator

A

True

84
Q

What is the velocity of the sound wave dependent on

A

The physical properties of the medium it travels through

85
Q

How fast does the sound wave move through bone

A

3360 m/sec

86
Q

How fast does the sound wave move through water

A

1500 m/sec

87
Q

How fast does the sound wave move through air

A

300 m/sec

88
Q

What is a couplant

A

Any agent that allows for smooth transmission of US from sound head to tissue

89
Q

What percent of the US does degassed water transmit

A

100%

90
Q

What percent of the US does mineral oil transmit

A

97%

91
Q

What percent of the US does US gel (ultraphonic) transmit

A

96%

92
Q

What percent of the US does US lotion (polysonic) transmit

A

90%

93
Q

What does non thermal US do

A

Alters cell membrane permeability

94
Q

True or False:

It may not be the cavitation that causes the effects it may be the frequency (resonant frequency)

A

True

95
Q

True or False:

Higher intensities and more continuous beam produces more vigorous vibration

A

True

96
Q

What is the absorption coefficient

A

The amount of absorption of US energy that occurs in a tissue type at a specific frequency

97
Q

True or False:

Absorption coefficient increases proportionally with US frequency

A

True

98
Q

What are the thermal effects of US (7)

A
  1. Increased extensibility of collagen fibers
  2. Reduced viscosity of fluid elements in tissues
  3. Decreased joint stiffness
  4. Reduced muscle spasm
  5. Diminished pain perception
  6. Increased metabolism
  7. Increased blood flow
99
Q

What is considered mild heating of tissue

A

1 C

100
Q

What is considered moderate heating of tissue

A

2-3 C

101
Q

What is considered vigorous heating of tissue

A

4 C

102
Q

What is the effect of mild heating (2)

A
  1. Increased metabolism

2. Reduces mild swelling

103
Q

What is the effect of moderate heating (2)

A
  1. Reduces pain and muscle spasm

2. Increases blood flow

104
Q

What is the effect of vigorous heating (1)

A
  1. Increases ROM and tissue extensibility
105
Q

How much does 1 MHz and 3 MHz increase tissue temperature per minute at 0.5 W/cm2

A

1 MHz: 0.04 C

3 MHz: 0.3 C

106
Q

How much does 1 MHz and 3 MHz increase tissue temperature per minute at 1.0 W/cm2

A

1 MHz: 0.2 C

3 MHz: 0.6 C

107
Q

How much does 1 MHz and 3 MHz increase tissue temperature per minute at 1.5 W/cm2

A

1 MHz: 0.3 C

3 MHz: 0.9 C

108
Q

How much does 1 MHz and 3 MHz increase tissue temperature per minute at 2.o W/cm2

A

1 MHz: 0.4 C

3 MHz: 1.4 C

109
Q

How long does the temperature change last for 1 MHz at 2.5 cm depth and 5 cm depth and 3 MHz 1.2 cm depth when temperature is raised 1 C

A

1 MHz 2.5 cm: 2:34
1 MHz 5 cm: 2:31
3 MHz 1.2 cm: 1:20

110
Q

How long does the temperature change last for 1 MHz at 2.5 cm depth and 5 cm depth and 3 MHz 1.2 cm depth when temperature is raised 2 C

A

1 MHz 2.5 cm: 6:35
1 MHz 5 cm: 6:50
3 MHz 1.2 cm: 3:22

111
Q

How long does the temperature change last for 1 MHz at 2.5 cm depth and 5 cm depth and 3 MHz 1.2 cm depth when temperature is raised 3 C

A

1 MHz 2.5 cm: 12:10
1 MHz 5 cm: 14:32
3 MHz 1.2 cm: 5:50

112
Q

How long does the temperature change last for 1 MHz at 2.5 cm depth and 5 cm depth and 3 MHz 1.2 cm depth when temperature is raised 4 C

A

1 MHz 2.5 cm: 21:14
1 MHz 5 cm: 27:49
3 MHz 1.2 cm: 9:13

113
Q

What are the non thermal effects of US (11)

A
  1. Increased histamine release
  2. Influx of Ca++
  3. Increased phagocytosis of macrophages
  4. Increased protein synthesis
  5. Increased capillary density of ischemic tissue
  6. Tissue regeneration
  7. Wound healing
  8. Cell membrane alteration
  9. Attraction of immune cells to injured tissues
  10. Increased fibroblast activity
  11. Vascular regeneration
114
Q

How do non thermal effects of US occur (3)

A
  1. Membrane deforms slightly due o pressure against cell wall
  2. frequency response theory
  3. Micromassage, microstreaming, and cavitation
115
Q

Where do most of the non thermal effect of US take place

A

The cell membrane

116
Q

What is the frequency response theory

A

Specific frequency will cause specific tissue resonance

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