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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
Rayleigh scattering is equal to __________
Frequency^4
26
Doubling the frequency = Rayleigh scattering that is ________.
16 times greater
27
What frequency sound waves have longer pulses and do not attenuate as fast?
Lower frequency sound wave
28
What frequency sound wave can travel deeper, but the image quality is not as good?
Lower frequency sound wave
29
What frequency sound wave have shorter pulses and have better image quality?
Shorter frequency sound wave
30
What frequency sound wave attenuate more and are less capable of traveling deep?
Shorter frequency sound wave
31
What are methods of rating numbers or values?
Logarithms
32
The _______________ is the number of 10s multiplied to create the original number.
Log of a number
33
What is the log of 1000?
3(10 x 10 x 10)
34
What is the log of 100,000?
5(10 x 10 x 10 x 10 x 10)
35
As the logarithm increases by 1, the number value increases by ___________.
10 times
36
What is an example of a logarithmic scale?
The Richter scale
37
What measures the strength of the sound beam created by the transducer as it travels through the body?
Dcibels (dB)
38
What compares the final strength to the initial strength of the decibles?
Logarithmic scale
39
What two intensities does decibels require?
The reference (starting point- transmission) The level at the time of measurement (reception)
40
True or false Decibels are a ratio
True
41
When a wave's intensity doubles, a relative change of +3dB is called_____
A positive decibel
42
A positive decibel, when increased 10- fold, will create a change of
+10dB
43
Decibel increase/ decrease will be reported in factors of ____ or ____
3 or 10
44
When a decrease in signal strength or getting smaller is called
A negative decibel
45
A negative decibel, if intensity is reduced in half, a relative change of ____ occurs
-3dB
46
When the intensity is reduced by 1/10, a change of ____ occurs
-10dB
47
The number of decibels of attenuation that occurs when sound travels one centimeter.
Attenuation coefficient
48
Attenuation occurs as a result of
Absorption Scattering Reflection
49
Attenuation is dependent on
Frequency the medium distance
50
The reporting of a waves _________________ is a process simplified by the attenuation coefficient.
total attenuation
51
Attenuation coefficient is measured in _____
dB/cm
52
True or false Attenuation coefficient remains fluctuates no matter how far it travels
False It stays the same
53
Once the attenuation coefficient has been determined, the distance is the only factor that will change a wave's ____________
Total attenuation
54
How do you determine the attenuation coefficient in soft tissue?
1/2 the frequency(MHz)= attenuation coefficient dB/cm
55
Scattering and frequency are ______ related
Directly
56
Attenuation and coefficient are measuring the ___________________.
loss of energy
57
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?
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
True or False To determine the attenuation coefficient in soft tissue, you just need to half the operating frequency.
True
59
What is the total attenuation of 12 MHz of sound traveling in soft tissue to reflectors that are 7 cm deep?
42 dB
60
Which medium has extremely high attenuation?
Air
61
Which medium has extremely low attenuation?
Water

Sonography (39 decks)

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