Sono Physics > Unit 3 > Flashcards

Unit 3 Flashcards

(55 cards)

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1
Q

What is the concentration of power in a beam?

A

Intensity

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2
Q

What are the 6 ways to measure intensity?

A

SPTP,SATP, SPTA, SATA,SPPA,SAPA

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3
Q

What is the weakening of the ultrasound beam as it travels in a medium?

A

Attenuation “The Toll”

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4
Q

Attenuation leads to a decrease in what?

A

Intensity and Amplitude

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5
Q

What is attenuation determined by?

A

1.) Frequency
2.) the distance the pulse travels.

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6
Q

The further the ultrasound travels the ___ the attenuation.

A

Greater

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7
Q

The higher the frequency, the ___ the attenuation.

A

Greater

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8
Q

Attenuation results from what three processes?

A

1.) Absorption
2.) Reflection
3.) Scattering

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9
Q

During ____ energy is lost by tissue heating.

A

Absorption

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10
Q

It is estimated ___ % or more of the total attenuation in soft tissue is caused by absorption.

A

80%

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11
Q

When sound changes direction as it reaches the boundary between two dissimilar media.

A

Reflection

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12
Q

Reflectors off of a smooth reflector. Such as a mirror.

A

Specular

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13
Q

When a wave hits a medium that is NOT smooth. It comes back scattered.

A

Diffuse

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14
Q

Reflections act to ____ the sound beam that continues to propagate deeper into the tissues.

A

Weaken

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15
Q

Occurs when a sound wave strikes a material whose size is appx equal or smaller than the wavelength of cycles in pulse.

A

Scattering

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16
Q

When a reflector is MUCH smaller than the sound’s wavelength. Ultrasonic energy is directed in all directions.

A

Rayleigh Scattering

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17
Q

The higher the frequency, the ____the amount of Rayleigh scattering.

A

greater

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18
Q

An interaction of ultrasound and RBCs results in what?

A

Rayleigh scattering

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19
Q

The amount of attenuation per cm of tissue.

A

Attenuation Coefficient

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20
Q

Attenuation Coefficient is directly related to what?

A

Frequency

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21
Q

The Attenuation Coefficient ranges from ___ to ___ dB/cm per MHz of frequency.

A

0.5-1.1dB/cm

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22
Q

Frequency divided by 2 is the equation for what?

A

Attenuation coefficient

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23
Q

Path length times attenuation coefficient is equation for what?

Study These Flashcards
A

Total attenuation

24
Q

In soft tissue, the higher the frequency, the higher the ______.

Study These Flashcards
A

Attenuation Coefficient

25
If the path length increases, attenuation will _____.
Increase
26
The attenuation coefficient is _____ in both lungs and bone.
higher
27
What is the acoustic resistance to sound traveling through a medium?
Impedance
28
Density times propagation speed is the equation for what?
Impedance
29
What two things will cause a medium to have a high impedance?
1.) It is very dense 2.) It has a fast propagation speed
30
What is another name for diffuse reflection?
Back scatter
31
If you increase the frequency, sound will ____ more.
scatter.
32
This occurs when the sound beam strikes the boundary between different tissues at exactly 90 degrees.
Normal incidence.
33
This occurs when a sound beam strikes a boundary between tissues at an angle OTHER than 90 degrees.
Oblique incidence.
34
The intensity of the wave that is about to strike a boundary between two different media.
Incident Intensity
35
The intensity that, after striking a boundary it continues traveling in the same general direction.
Transmitted Intensity
36
The intensity that, after striking a boundary between two dissimilar tissues, changes direction and returns in the same direction it came from.
Reflected Intensity
37
___% of the incident intensity is reflected back towards the transducer at a boundary between soft tissue.
1% or less.
38
____% of a wave's intensity is reflected at a boundary between bone and soft tissue.
30-50%
39
What is calculated by dividing the reflected intensity by the incident intensity?
Intensity Reflection Coefficient (IRC)
40
What is calculated by dividing the transmitted intensity by the incident intensity?
Intensity Transmitted Coefficient (ITC)
41
If the IRC increases, then the ITC will____.
Decrease.
42
What is the percent of ultrasound intensity that is allowed to pass through when the beam strikes a boundary between two media called?
Intensity Transmitted Coefficient (ITC)
43
A change in direction or a bending from a straight line path of a wave traveling from one medium to another.
Refraction
44
Refractions only occur with what two conditions?
1.) Different propagation speeds 2.) Oblique incidence.
45
Refractions can NOT occur with what two conditions?
1.) Normal incidence 2.) Same propagation speeds.
46
Snell's Law describes what?
Refraction.
47
(Media 2 -Media 1) divided by (Media 2 + Media 1) squared is the equation for what?
IRC
48
What measurement will determine the average intensity during the most intense half-cycle?
IMAX
49
Reflected intensity + transmitted intensity is what?
Incident Intensity
50
All intensities are measured in
W/cm squared
51
If frequency is increased, Raleigh scattering will ____.
Increase
52
For every 13 microseconds of Go-Return time is equal to the object being ____ deep into the body.
1 cm (13 microsecond rule)
53
Rank of intensities.
SPTP>IMAX>SPPA>SPTA> SATA
54
What two variables are needed to calculate range?
1.) Propagation Speed 2.) Go-Return Time
55
Speed of sound times Go-Return speed divided by 2 is the____.
Range Equation.
Sono Physics
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