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Vascular I & Physics I > Ch. 5-7 Test > Flashcards

Ch. 5-7 Test Flashcards

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1
Q

Key parameter for bioeffects. It is the concentration of the power in a beam

A

intensity

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2
Q

What is the maximum value called

A

peak

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3
Q

What is the mean or average value called

A

average

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4
Q

Refers to distance or space

A

Spatial

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5
Q

Refers to all time (transmit and receive)

A

temporal

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6
Q

Refers only to the time the pulse exists (transmit only)

A

pulsed

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7
Q

All intensities have units of

A

w/cm squared

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8
Q

The largest intensity is

A

SPTP

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9
Q

The smallest intensity is

A

SATA

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10
Q

The intensity which is most important for thermal bioeffects is

A

SPTA

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11
Q

Intensities may be reported in various ways with respect to

A

time and space

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12
Q

As sound travels in the body it _______ or _______

A

weakens or attenuates

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13
Q

After a sound wave is received by the transducer and ________ into _______ and returned to the ultrasound system, it is _________ or ________

A

converted, electricity, strengthened, amplified

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14
Q

Decibels are a ______ scale.

A

logarithm

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15
Q

The _____ of any number represents the number of “10s” that are multiplied together to create the original number

A

log

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16
Q

What is the log of 100

A

2

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17
Q

What is the log of 10000

A

4

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18
Q

How many intensities are required to use decibels

A

two

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19
Q

Decibels are a ratio of the _________ to the _______

A

measured level, starting level

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20
Q

The ______ level is ______ by the starting level

A

measured, divided

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21
Q

What are the units of relative amplitude

A

dB

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22
Q

Positive decibels report signals that are ______ in strength or getting larger

A

increasing

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23
Q

Negative decibels report signals that are ______ in strength or getting smaller

A

decreasing

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24
Q

What dB means two times bigger or double

A

+3dB

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25
Q

What dB means ten times bigger or ten fold

A

+10dB

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26
Q

What dB means one half

A

-3dB

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27
Q

What dB means one tenth

A

-10dB

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28
Q

6dB means the final is _____ times bigger than the original

A

4

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29
Q

20 dB means the final is ______ times bigger than the original

A

100

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30
Q

-20dB means the final has fallen to ______ the original value

A

1/00

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31
Q

-6dB means the final has fallen to ________ the original value

A

1/4

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32
Q

A signal’s power increases from 1 to 100 watts. How is this expressed in decibels

A

20dB (10 x 10= 100)

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33
Q

The power of a system is at 100% and this is 0dB. What is the change in decibels when the system’s power is at 50%

A

-3dB

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34
Q

The power of a system is at 100% and this is 0dB. The system is adjusted to -6dB. What is the system’s power at this setting

A

25%

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35
Q

The decrease in intensity, power and amplitude of a sound wave as it travels

A

attenuation

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36
Q

The further a sound wave travels, the more

A

attenuation occurs

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37
Q

Attenuation of sound in soft tissue depends upon the wave’s _____ and the ______ the wave travels

A

frequency, distance

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38
Q

In soft tissue, ____ frequency results in less attenuation resulting in deeper imaging

A

lower

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39
Q

Distance and attenuation are

A

directly related

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40
Q

Frequency and attenuation are

A

directly related

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41
Q

list the 3 components of attenuation

A

reflection, absorption and scattering

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42
Q

The primary component of attenuation and occurs when the sound energy is converted into heat energy

A

absorption

43
Q

What has extremely high attenuation than soft tissue

A

air

44
Q

____ and ____ have more attenuation than soft tissue

A

bone, air

45
Q

What has much, much less attenuation than soft tissue

A

water

46
Q

Higher attenuation occurs with ____ because it absorbs and reflects

A

air

47
Q

Higher attenuation occurs with _____ because of scattering and absorption

A

lung

48
Q

Occurs when propagating sound energy strikes a boundary between two media and some returns to the transducer

A

reflection

49
Q

Occurs when the boundary is smooth and sound is reflected in only one direction in an organized manner

A

specular

50
Q

Occurs when the irregularities in the structure’s surface are much smaller than the wavelength

A

rayleigh scattering

51
Q

Reflections that move out equally in all directions

A

omnidirectional/rayleigh

52
Q

Occurs when the boundary has irregularities about the same size as the sound’s wave length

A

diffuse reflection or backscattering

53
Q

When a boundary is ______, reflected sound is disorganized and random

A

irregular

54
Q

Backscatter is also called

A

diffuse reflection

55
Q

Random redirection of sound in many directions

A

scattering

56
Q

Rayleigh scattering when the tissue interface is _______ or _______ than the wavelength of the incident sound beam

A

organized, much smaller

57
Q

Lung tissue scatters sound because the alveoli are filled with

A

air

58
Q

Rayleigh scattering=

A

frequency^4

59
Q

Number of decibels of attenuation that occurs when sound travels one centimeter

A

attenuation coefficient

60
Q

The units for attenuation coefficient are

A

dB, cm (dB/cm)

61
Q

The value of the _____ DOES NOT CHANGE as path length changes

A

attenuation coefficient

62
Q

In soft tissue, the attenuation coefficient is

A

0.5 dB/cm/MHz

63
Q

Attenuation is extremely high in

A

air, lung and bone

64
Q

Attenuation is extremely low in

A

fat, water and biological fluids

65
Q

Gel is used to remove ______ from the path of ultrasound

A

air

66
Q

Acoustic resistance to sound traveling in a medium

A

impedance

67
Q

Impedance=

A

density x prop speed

68
Q

The units for impedance are

A

rayls

69
Q

Rayls are represented by

A

z

70
Q

Normal incidence means that the incident sound beam strikes the boundary at

A

90 degrees

71
Q

What are the other names for normal incidence

A

perpendicular, orthogonal, right angle, 90 degrees

72
Q

Oblique incidence occurs when the incident sound beam strikes the boundary at any angle

A

other than 90 degrees

73
Q

Sound wave’s intensity immediately before it strikes a boundary

A

incident intensity

74
Q

Intensity of the portion of the incident sound beam that, after striking a boundary, returns back in the direction from which it came

A

reflection intensity

75
Q

Intensity of the portion of the incident beam that, after striking a boundary, continues forward in the same general direction that it was traveling

A

transmission intensity

76
Q

There is __________ of ______ at a boundary, which means the incident intensity equals reflected + transmitted intensities

A

conservation of energy

77
Q

Incident intensity=

A

reflected intensity + transmitted intensity

78
Q

Percentage of the intensity that bounces back when a sound beam strikes the boundary between two media

A

Intensity reflection coefficient (IRC)

79
Q

Percentage of the intensity that passes in the forward direction when the beam strikes an interface between two media

A

Intensity transmitted coefficient (ITC)

80
Q

IRC + ITC=

A

100% (incident intensity)

81
Q

Intensities are reported with units of

A

w/cm squared

82
Q

Intensity coefficients are reported with

A

percentages

83
Q

In soft tissue, ______ of the incident US energy is reflected at a soft-tissue boundary between different biologic media

A

less than 1%

84
Q

How much is reflected at an air-tissue interface

A

> 99%

85
Q

How much is reflected at a bone-tissue interface

A

greater %

86
Q

If the intensity reflection coefficient of sound is 99.9% at an air tissue interface, what percent of sound is transmitted into the body

A

0.1%

87
Q

A sound beam with the intensity of 45 w/cm squared strikes a boundary and 70% is transmitted, how much is reflected

A

30%

88
Q

Reflection with _______ occurs only if the two media at the boundary have different acoustic impedances

A

normal incidence

89
Q

Whatever is not transmitted must be

A

reflected

90
Q

Reflection and transmission with ________ MAY OR MAY NOT occur

A

oblique incidence

91
Q

With oblique incidence, reflection angle equals

A

incidence angle

92
Q

Refraction is ______ with a bend

A

transmission

93
Q

Change in direction as sound transmits from one medium to another at an oblique angle

A

refraction

94
Q

Refraction requires two conditions to be met

A

oblique incidence, 2 different media prop speeds

95
Q

Refraction cannot occur with

A

normal incidence, 2 media with same speed

96
Q

Describes the physics of refraction

A

snell’s law

97
Q

Sound wave strikes a boundary at normal incidence. The impedance of the two media are identical. What percentage of the sound wave is refracted

A

0%

98
Q

The impedance of medium 1 is 8 rayls and the prop speed is 1450 m/sec. The impedance of medium 2 is 6 rayls and the prop speed is 1.855 km/s. A sound beam strikes a boundary between the media and is both partially transmitted and reflected. The angle of the incident sound beam is 30 degrees. What is the angle of reflection

A

30 degrees (angle of incidence=angle of reflection)

99
Q

The elapsed time from pulse creation to the pulse reception is called the

A

go-return time or time-of-flight

100
Q

The time-of-flight is directly related to

A

how deep a sound wave travels

101
Q

In soft tissue, every _____ of go-return time means the reflector is 1 cm deeper in the body

A

13 microseconds

102
Q

When a reflector is 3cm deep, a pulse’s time-of-flight is

A

39 miscroseconds

103
Q

A sound pulse is produced by a transducer and travels in a patient. It travels from the transducer to the kidney, reflects off of it and returns to the transducer in 130 microseconds. How deep is the kidney

A

10cm

104
Q

A sound pulse emitted from a transducer travels in a patient, reflects off of the pancreas and returns to the transducer is 52 microseconds. How deep is the pancreas? What is the total distance that the pulse traveled?

A

4cm, 8cm

Vascular I & Physics I (19 decks)

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