Ultrasound Flashcards Preview

Phys Agents > Ultrasound > Flashcards

Flashcards in Ultrasound Deck (116):
1

Is US audible to the human ear

No

2

How is US generated

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

3

What is the crystal made of and it's thickness

Synthetic ceramic 2-3 mm

4

What does the crystal convert electrical energy to

Mechanical acoustic energy

5

True or False:
US creates a reverse piezoelectric effect

True

6

What is the reverse piezoelectric effect

Voltage creating a mechanical compression to the crystal

7

What is the soundhead made of (3)

Ceramic, aluminum, or stainless steel plate

8

Is the soundhead interchangeable and why or why not

No because it generally matches the frequency of the crystal

9

What does the applicator house (2)

1. Crystal
2. Soundhead

10

What is the applicator made out of

Hard insulated plastic

11

What type of wave do photons move along the wave

Electromagnetic

12

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

Mechanical

13

What are the 2 types of therapeutic ultrasound waves

1. Longitudinal waves
2. Transverse waves

14

Can sound waves travel through a vacuum why or why not

No because they need to be able to bump into something

15

True or False:
US creates a wave that goes positive and negative

True

16

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

Transverse waves

17

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

Longitudinal waves

18

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

Microstreaming

19

What is the near field

Area of the US beam closest to transducer

20

What is another name for the near field

Fresnel zone

21

What is the far field

Area of the US beam where wave begins to diverge

22

What is another name for the far field

Fraunhofer zone

23

What does the near field look like

Sound waves are transmitted in a straight line

24

What does the far field look like

Sound wave begins to diverge or scatter

25

What are rarefactions

Dispersion of molecules

26

When do rarefactions occur during US

The peak of the wave

27

When does compression occur during US

The valley of the wave

28

What is power

Amount of energy per unit of time

29

1W equals what

1 joule/sec

30

What is 1 joule equal to

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

31

What is a joule equal to in foot pounds

0.738 foot pounds

32

What is the effective radiating area (ERA)

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

33

What is the ERA dependent on

The size of the crystal

34

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

Smaller

35

What is the ERA measured in

cm2

36

What are the 2 variables that pertain to intensity of US

1. Spatial
2. Temporal

37

What is spatial intensity variable

Relates to the size of transducer ERA

38

What is temporal intensity variable

Relates to time transducer is on

39

How do you determine the spatial average intensity

Power/ERA

40

What is spatial peak intensity

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

41

Where is the spatial peak intensity the greatest

The center of the US beam

42

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

Spatial average temporal peak (SATP) * Duty cycle

43

What does SATA measure

The amount of energy delivered to tissue

44

What is beam nonuniformity ratio (BNR) technical terms

Ratio of spatial peak intensity to spatial average intensity

45

What is beam nonuniformity ratio (BNR) dumby terms

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

46

What does a lower BNR mean

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

47

What is the recommended range for BNR values

2:1 and 8:1

48

What is the duty cycle

The percent of time the US beam is on

49

What does a continuous duty cycle mean

The US beam is always on

50

What does a pulsed duty cycle mean

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

51

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

Pulse

52

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

Continuous

53

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

Continuous

54

What does the pulse duty cycle do

Limits the amount of energy put in the patient

55

What is the frequency equivalent to for US

The number of compression-rarefaction cycles per unit of time

56

What is the frequency range for TUS

0.75 MHz to 3.3 MHz

57

How deep does 1 MHz US penetrate

Up to 5 cm

58

How deep does 3 MHz US penetrate

1-2 cm

59

True or False:
Absorption decreases as frequency increases

False

60

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

1/3 the time

61

What is absorption considered

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

62

What types of tissues absorb US the best

Tissues high in collagen

63

What is reflection

Redirection of the US beam away from the surface

64

How much does the soft tissue bone interface reflect US

35%

65

How much does the skin air interface reflect US

100%

66

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

0.1%

67

What is refraction

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

68

What does attenuation measure

The decrease in US intensity as the wave travels through tissues

69

What causes the intensity of US to decrease (2)

1. Absorption of US wave by tissue
2. Dispersion of US wave due to reflection and refraction

70

What types of tissues have higher attenuation coefficients

Tissues with higher collagen content

71

True or False:
Penetration and absorption of the US beam are inversely proportional to one another

True

72

What happens to absorption as frequency increases

Absorption increases

73

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

True

74

How do you minimize standing waves

Keep the sound head moving

75

What is cavitation

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

76

What is the compression phase

The bubbles compress

77

What is the rarefaction phase

The bubbles expand

78

True or False:
Cavitation can be stable or unstable

True

79

True or False:
Stable cavitation is thought to produce a thermal effect of US

False

80

Does true unstable cavitation occur at the therapeutic level

NOOOOOO!!!!!!!

81

What is microstreaming

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

82

What is microstreaming a result of

Pressure of the sound wave that moves ions or small molecules

83

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

True

84

What is the velocity of the sound wave dependent on

The physical properties of the medium it travels through

85

How fast does the sound wave move through bone

3360 m/sec

86

How fast does the sound wave move through water

1500 m/sec

87

How fast does the sound wave move through air

300 m/sec

88

What is a couplant

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

89

What percent of the US does degassed water transmit

100%

90

What percent of the US does mineral oil transmit

97%

91

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

96%

92

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

90%

93

What does non thermal US do

Alters cell membrane permeability

94

True or False:
It may not be the cavitation that causes the effects it may be the frequency (resonant frequency)

True

95

True or False:
Higher intensities and more continuous beam produces more vigorous vibration

True

96

What is the absorption coefficient

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

97

True or False:
Absorption coefficient increases proportionally with US frequency

True

98

What are the thermal effects of US (7)

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

What is considered mild heating of tissue

1 C

100

What is considered moderate heating of tissue

2-3 C

101

What is considered vigorous heating of tissue

4 C

102

What is the effect of mild heating (2)

1. Increased metabolism
2. Reduces mild swelling

103

What is the effect of moderate heating (2)

1. Reduces pain and muscle spasm
2. Increases blood flow

104

What is the effect of vigorous heating (1)

1. Increases ROM and tissue extensibility

105

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

1 MHz: 0.04 C
3 MHz: 0.3 C

106

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

1 MHz: 0.2 C
3 MHz: 0.6 C

107

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

1 MHz: 0.3 C
3 MHz: 0.9 C

108

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

1 MHz: 0.4 C
3 MHz: 1.4 C

109

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

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

110

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

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

111

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

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

112

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

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

113

What are the non thermal effects of US (11)

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

How do non thermal effects of US occur (3)

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

115

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

The cell membrane

116

What is the frequency response theory

Specific frequency will cause specific tissue resonance