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Sonography > Ch. 6 Physics: Interaction of sound and media > Flashcards

Ch. 6 Physics: Interaction of sound and media Flashcards

1
Q

The intensity, power, and amplitude of the sound wave weakens as it passes through tissue

A

Attenuation

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2
Q

What creates the images?

A

Reflections

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3
Q

Weak reflections are often created as a sound strikes a ______ between two different media.

A

Boundary

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4
Q

Sound wave that is sent out is 100%, what is the sound wave when it returns?

A

20%

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5
Q

What determines the attenuation?

A

Path length and frequency

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6
Q

Distance and frequency are __________ related to attenuation

A

Directly related

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7
Q

What are the units for attenuation?

A

dB (decibels)

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8
Q

What processes contribute to attenuation?

A

Absorption
reflection
scattering

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9
Q

What processes is the primary component of attenuation?

A

Absorption

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10
Q

Whats the relationship for absorption and frequency>

A

Directly

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11
Q

True or false:
Higher frequency waves attenuate more than lower frequency waves

A

True

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12
Q

What is it called when the boundary is smooth, the sound is reflected in only one direction in an organized manner?

A

Specular reflection

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13
Q

What is another name for backscatter?

A

Diffuse reflection

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14
Q

When the sound beam strikes an irregular surface, reflections radiate in multiple directions

A

Diffuse reflection

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15
Q

True or false
Backscattered signals have a higher strength than specular reflections in diffuse refelction.

A

False
They have lower strength

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16
Q

Whats the random redirection of sound from the primary path into many directions?

A

Scattering

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17
Q

What occurs when the tissue interface is smaller than or equal to the wavelength of the primary beam?

A

Scattering

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18
Q

______ allows us to see the tissue interface.

A

Scattering

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19
Q

Scattering is _______ related to frequency

A

Directly

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20
Q

What is a redirection of the sound wave equally in all directions?

A

Rayleigh Scattering

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21
Q

True or false
Rayleigh scattering is organized scattering

A

True

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22
Q

Occurs when the structure is much smaller than the beams wavelength

A

Rayleigh Scattering

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23
Q

A blood cell is considered a _______

A

Rayleigh scatterer

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24
Q

Rayleigh scattering is related to frequency
True or false

A

True

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25
Q

Rayleigh scattering is equal to __________

A

Frequency^4

26
Q

Doubling the frequency = Rayleigh scattering that is ________.

A

16 times greater

27
Q

What frequency sound waves have longer pulses and do not attenuate as fast?

A

Lower frequency sound wave

28
Q

What frequency sound wave can travel deeper, but the image quality is not as good?

A

Lower frequency sound wave

29
Q

What frequency sound wave have shorter pulses and have better image quality?

A

Shorter frequency sound wave

30
Q

What frequency sound wave attenuate more and are less capable of traveling deep?

A

Shorter frequency sound wave

31
Q

What are methods of rating numbers or values?

A

Logarithms

32
Q

The _______________ is the number of 10s multiplied to create the original number.

A

Log of a number

33
Q

What is the log of 1000?

A

3(10 x 10 x 10)

34
Q

What is the log of 100,000?

A

5(10 x 10 x 10 x 10 x 10)

35
Q

As the logarithm increases by 1, the number value increases by ___________.

A

10 times

36
Q

What is an example of a logarithmic scale?

A

The Richter scale

37
Q

What measures the strength of the sound beam created by the transducer as it travels through the body?

A

Dcibels (dB)

38
Q

What compares the final strength to the initial strength of the decibles?

A

Logarithmic scale

39
Q

What two intensities does decibels require?

A

The reference (starting point- transmission)
The level at the time of measurement (reception)

40
Q

True or false
Decibels are a ratio

A

True

41
Q

When a wave’s intensity doubles, a relative change of +3dB is called_____

A

A positive decibel

42
Q

A positive decibel, when increased 10- fold, will create a change of

A

+10dB

43
Q

Decibel increase/ decrease will be reported in factors of ____ or ____

A

3 or 10

44
Q

When a decrease in signal strength or getting smaller is called

A

A negative decibel

45
Q

A negative decibel, if intensity is reduced in half, a relative change of ____ occurs

A

-3dB

46
Q

When the intensity is reduced by 1/10, a change of ____ occurs

A

-10dB

47
Q

The number of decibels of attenuation that occurs when sound travels one centimeter.

A

Attenuation coefficient

48
Q

Attenuation occurs as a result of

A

Absorption
Scattering
Reflection

49
Q

Attenuation is dependent on

A

Frequency
the medium
distance

50
Q

The reporting of a waves _________________ is a process simplified by the attenuation coefficient.

A

total attenuation

51
Q

Attenuation coefficient is measured in _____

A

dB/cm

52
Q

True or false
Attenuation coefficient remains fluctuates no matter how far it travels

A

False
It stays the same

53
Q

Once the attenuation coefficient has been determined, the distance is the only factor that will change a wave’s ____________

A

Total attenuation

54
Q

How do you determine the attenuation coefficient in soft tissue?

A

1/2 the frequency(MHz)= attenuation coefficient dB/cm

55
Q

Scattering and frequency are ______ related

A

Directly

56
Q

Attenuation and coefficient are measuring the ___________________.

A

loss of energy

57
Q

You are scanning soft tissue with a 6 MHz transducer. Your depth of view is 5 cm.
What is your attenuation coefficient?
What is your total attenuation?

A

Atten. Coef. = 3 dB/cm
Total atten= 15 dB

atten coef (dB/cm)= frequency (MHz)/ 2

Total atten (dB)= atten coef (dB/cm) X distance (cm)

6MHz / 2 = 3 dB/cm

3dB/cm x 5 cm = 15 dB

58
Q

True or False
To determine the attenuation coefficient in soft tissue, you just need to half the operating frequency.

A

True

59
Q

What is the total attenuation of 12 MHz of sound traveling in soft tissue to reflectors that are 7 cm deep?

A

42 dB

60
Q

Which medium has extremely high attenuation?

A

Air

61
Q

Which medium has extremely low attenuation?

A

Water

Sonography (39 decks)

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