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Intro > Ch. 6 Interaction of Sound and Media > Flashcards

Ch. 6 Interaction of Sound and Media Flashcards

1
Q

Sound waves weaken, or ______ as they travel through the body.

A

Sound waves weaken, or attenuate as they travel through the body.

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2
Q

After a transducer receives a sound wave during reception, the sound wave is converted into electrical sound. The signal is sent to the ultrasound system where it is strengthened or _____________________.

A

After a transducer receives a sound wave during reception, the sound wave is converted into electrical sound. The signal is sent to the ultrasound system where it is strengthened or amplified

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3
Q

Decibels are based on a mathematical construct called ______.

A

Decibels are based on a mathematical construct called logarithms

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4
Q

A _________ is a number that represents the number of 10s that are multiplied to create the original number.

A

A log is a number that represents the number of 10s that are multiplied to create the original number.

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5
Q

What is the log of 1,000?

A

We multiply 10 by itself 3 times to create the number 1,000 so the log of 1,000 is 3

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6
Q

Decibel notation does not measure absolute numbers; rather decibels report ________________ changes.

A

Decibel notation does not measure absolute numbers; rather decibels report relative changes

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7
Q

Positive decibels report signals that are ______ in strength or getting _______.

A

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

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8
Q

When a waves intensity doubles, the relative change is ______.

A

When a waves intensity doubles, the relative change is postive 3 decibels

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9
Q

When intensity increases ten-fold, the relative change is ________.

A

When intensity increases ten-fold, the relative change is positive 10 decibels

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10
Q

Negative decibels describe signals that are ______________ in strength, or getting ________________.

A

Negative decibels describe signals that are decreasing in strength, or getting smaller.

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11
Q

When the intensity is reduced to 1/2 its original value, the relative change is _____________.

A

When the intensity is reduced to 1/2 its original value, the relative change is negative 3 decibels

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12
Q

When the intensity is reduced to 1/10 its original value the relative change is ______.

A

When the intensity is reduced to 1/10 its original value the relative change is negative 10 decibels

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13
Q

Every 3dB change means that the intensity will ____.

A

double

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14
Q

Every 10dB change means that the intensity will _____.

A

increase ten times

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15
Q

A reduction in the intensity of a sound beam to one-half of its original value is _____ dB.

A

-3dB

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16
Q

A reduction in the intensity of a sound beam to one-quarter of its original value is _____ dB.

A

-6dB

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17
Q

-10dB means that the intensity is reduced to __________ of its original value.

A

-10dB means that the intensity is reduced to one-tenth of its original value.

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18
Q

If the final intensity of a sound beam is more than the initial intensity, then the gain in dB is ____. (+ or -)

A

Positive. The beams intensity is increasing.

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19
Q

If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is _____

A

Positive. The beams intensity is increasing.

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20
Q

Attenuation is determined by TWO factors:

A
  1. PATH LENGTH ( distance)
  2. FREQUENCY ( penetration)
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21
Q

Distance and attenuation are ______ related.

A

directly

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22
Q

Frequency and attenuation are ______ related.

A

directly

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23
Q

with longer distances and higher frequencies there is _____________ attenuation.

A

with longer distances and higher frequencies there is more attenuation

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24
Q

with shorter distances and lower frequencies there is _____________ attenuation.

A

with shorter distances and lower frequencies there is less attenuation

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25
Q

What three processes contribute to attenuation?

A
  1. Reflection
  2. Scattering
  3. Absorption
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26
Q

As sound strikes a boundary, a portion of the wave’s energy may be redirected, or _____ back to the sound source

A

reflected

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27
Q

What are the two forms of reflection?

A
  1. Specular
  2. Diffuse
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28
Q

When the boundary is smooth and the sound is reflected in only one direction in an organized manner. This is called?

A

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

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29
Q

Most interfaces in the body are not smooth, but have irregularities. When a wave reflects off an irregular surface, it radiates in more than one direction. This is called?

A

Diffuse Reflection or Backscatter is when a wave reflects off an irregular surface, it radiates in more than one direction

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30
Q

_____________________ is the random redirection of sound in many directions.

A

Scattering is the random redirection of sound in many directions.

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31
Q

Higher frequency sound beams scatter _______________ (more or less) than lower frequency beams.

A

more

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32
Q

Scattering is ______ related to frequency.

A

directly

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33
Q

______________________________ is a special form of scattering that occurs when the structures dimensions are much smaller than the beams wavelength.

A

Rayleigh Scattering is a special form of scattering that occurs when the structures dimensions are much smaller than the beams wavelength.

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34
Q

In clinical imaging, the interaction of ultrasound and ________________________________ results in rayleigh scattering.

A

In clinical imaging, the interaction of ultrasound and red blood cells results in raylegh scattering.

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35
Q

Scattering is related to _________.

A

Frequency raised to the fourth power

36
Q

When frequency doubles, Rayleigh Scattering is ________ times greater

A

When frequency doubles, Rayleigh Scattering is 16 times greater

37
Q

organized sound back to the transducer is ____________________ reflection

A

organized sound back to the transducer is Specular Reflection

38
Q

disorganized sound back to the transducer is _____________________ reflection

A

disorganized sound back to the transducer is Diffuse Reflection or Backscatter

39
Q

organized sound in all directions is _______________________________

A

organized sound in all directions is Rayleigh Scattering

40
Q

disorganized sound in all directions is ____________________________

A

disorganized sound in all directions is Scattering

41
Q

_________________________ occurs when ultrasonic energy is converted into another energy form, such as heat.

A

Absorption occurs when ultrasonic energy is converted into another energy form, such as heat.

42
Q

__________________________________ is the number of decibels of attenuation that occurs when sound travels one centimeter.

A

Attenuation Coefficient is the number of decibels of attenuation that occurs when sound travels one centimeter.

43
Q

what are the units for attenuation coefficient?

A

dB/cm

44
Q

Total Attenuation =

A

attenuation coefficient (dB/cm) x distance (cm)

45
Q

In soft tissue the attenuation coefficient is _______________ the frequency.

A

In soft tissue the attenuation coefficient is one-half the frequency

46
Q

attenuation coefficient formula:

A

frequency (MHz)/2

47
Q

Attenuation for each:
Water
Blood, Urine, Biologic Fluids
Fat
Soft Tissue
Muscle
Bone & Lung
Air

A

Water = extremely low
Blood, Urine, Biologic Fluids = low
Fat = low
Soft Tissue = intermediate
Muscle = higher
Bone & Lung = even higher
Air = extremely high

48
Q

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

A

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

49
Q

Half-Value Layer is also called: _______________________________, ______________________________, & _____________________________________.

A

Half Value Layer is also called: penetration depth, depth of penetration, half-boundary layer

50
Q

A high frequency sound and media with a high attenuation rate will have a _____________ Half-Value

A

A high frequency sound and media with a high attenuation rate will have a Thin Half-Value

51
Q

A low frequency sound and media with low attenuation rate will have a ___________ Half-Value

A

A low frequency sound and media with low attenuation rate will have a Thick Half-Value

52
Q

The half-value layer thickness depends on two factors:

A
  1. The medium
  2. the frequency of sound
53
Q

_____________________ is the acoustic resistance to sound traveling in a medium and is calculated by multiplying the density of a medium by the speed at which sound travels in the medium.

A

Impedance is the acoustic resistance to sound traveling in a medium and is calculated by multiplying the density of a medium by the speed at which sound travels in the medium

54
Q

Impedance is reported in what units?

A

Rayls (Z)

55
Q

Impedance is determined by

A

the medium, calculated not measured

56
Q

Name three components of attenuation:

A
  1. Absorption
  2. Reflection
  3. Scattering
57
Q

As the path length increases, the attenuation of ultrasound in soft tissue _______.

A

increases

58
Q

Attenuation in lung tissue is [less than, greater than, the same as] attenuation in soft tissue.

A

greater than

59
Q

Attenuation in bone is _________ attenuation in soft tissue.

A

greater than

60
Q

Attenuation in air is _______ attenuation in soft tissue.

A

greater than

61
Q

What are the units of attenuation?

A

decibels (dB)

62
Q

What are the units of the half-value layer thickness?

A

distance: centimeters

63
Q

Impedance is associated with ____________________.

A

only the medium

64
Q

Acoustic Impedance = ______________________ x __________________________

A

Acoustic Impedance = density (kg/m^3) multipled by propagation speed (m/s)

65
Q

Impedance is important in ____ at boundaries.

A

reflections

66
Q

_________________ incidence means that the incident sound beam strikes the boundary at exactly 90 degrees

A

Normal Incidence means that the incident sound beam strikes the boundary at exactly 90 degrees

67
Q

Normal incidence is also called ____________________________, ________________________, _________________________, & _______________________________.

A

Normal Incidence is also called:
- Perpendicular
- Orthogonal
- Right Angle
- 90 degrees

68
Q

_____________________ incidence occurs when the incident sound beam strikes the boundary at any angle other than 90 degrees

A

Oblique Incidence occurs when the incident sound beam strikes the boundary at any angle other than 90 degrees

69
Q

Incident intensity = ____________________________ + ______________________________

A

Incident Intensity = reflected intensity + transmitted intensity

70
Q

___________________________ is the intensity of the portion of the incident sound beam that, after striking a boundary, returns back where it came.

A

Reflected Intensity is the intensity of the portion of the incident sound beam that, after striking a boundary, returns back where it came.

71
Q

_____________________________ is the intensity of the portion of the incident sound beam that, after striking a boundary, continues forward in the same general direction that it was traveling.

A

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

72
Q

The _______________________________________ is the percentage of the intensity that bounces back when a sound beam strikes the boundary between two media

A

The Intensity Reflection Coefficient (IRC) is the percentage of the intensity that bounces back when a sound beam strikes the boundary between two media

73
Q

IRC formula

A

Intensity reflected divided by initial intensity

74
Q

If the reflected and transmitted intensities are added, the result must be the?

A

The incident intensity

75
Q

ITC formula

A

the transmitted intensity divided by incident intensity multiplied by 100

or

1 - intensity reflection coefficient

76
Q

if IRC and ITC are added the result must equal?

A

100%

77
Q

Sound is traveling from bone to soft tissue. The impedances of the media differ significantly, and 90% of the beam’s intensity is reflected. What percentage of the intensity is transmitted?

A

100% of the energy must be counted for. If 90% is reflected, 10% must be transmitted.

78
Q

When a sound beam strikes a tissue boundary at 90 degree angle, it is a ________________________ incidence

A

When a sound beam strikes a tissue boundary at a 90 degree angle, it is a normal incidence

79
Q

reflection occurs only if the media on either side of the boundary have _______________________ impedances

A

reflection occurs only if the media on either side of the boundary have different impedances

80
Q

With an oblique incidence, two physical priciples always apply to reflection:

A
  1. conservation of energy
  2. reflection angle = incident angle
81
Q

_____________________ is a change in direction of wave propagation when traveling from one medium to another.

A

Refraction is a change in direction of wave propagation when traveling from one medium to another.

82
Q

Refraction only occurs if two conditions are satisfied:

A
  1. oblique incidence
  2. different propagation speeds of the two media
83
Q

C2 = C1

A

no refraction; transmission angle = incident angle

84
Q

Which of the following terms does not belong with the others?
A. orthogonal
B. oblique
C. normal
D. perpendicular

A

B. Oblique means “other than 90 degrees”

The other three terms all have the meaning of “equal to 90 degrees”

85
Q

C2 > C1 =

A

transmission angle greater than incident angle

86
Q

The ______________________________________ is the percentage of the intensity that continues to move forward when the beam reaches a boundary between two media.

A

The Intensity Transmission Coefficient is the percentage of the intensity that continues to move forward when the beam reaches a boundary between two media

87
Q

C2 < C1 =

A

transmission angle less than incident angle

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