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Physics 1 > Lesson 7 > Flashcards

Lesson 7 Flashcards

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1
Q

What 3 things make up attenuation?

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

Attenuation

A

Weakening of sound

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3
Q

What is the result of weaker signals?

A

Weaker echoes

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4
Q

What structures produce weaker signals?

A

Structures that are farther away

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5
Q

Where is the near field?

A

Closest are to the transducer

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6
Q

Where is the mid field?

A

Between the near field and the far field

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7
Q

Where is the far field?

A

Farthest area to the transducer

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8
Q

What happens to sound as it goes through a medium?

A

It gets weaker

- has to go through and come back

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9
Q

What do we use that can fix attenuation?

A

TGC

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10
Q

What does TGC stand for?

A

Time gain compensation

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11
Q

Whats another word for TGC?

A

DGC

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12
Q

What does DGC stand for?

A

Depth gain compensation

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13
Q

What does the TGC slope provide?

A

Amplification of specific field echoes

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14
Q

What does TGC do?

A

It amplifies the far field to promote uniform in tissues

- eg) liver

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15
Q

What does it mean when your TGC is straight on the ultrasound machine?

A

You are getting equal amounts of amplification

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16
Q

What does it mean when your TGC is on a diagonal on the machine?

A

You get amplification in different spots

- leads to a more uniform image

17
Q

What is the formula for attenuation in soft tissues?

A 
a = 1/2f x L
a = attenuation 
f = frequency 
L = length/distance/thickness
18
Q

How does attenuation occur in soft tissues?

A
  1. 5 there and 0.5 back = 1
    - dB/cm x MHz
    - compensates for both directions
19
Q

What 2 things does overall gain do?

A
  1. Amplification of entire field of view

2. Amplification of all incoming echo voltages

20
Q

What is attenuation’s unit?

A

Decible

- dB

21
Q

How much is 3db? (2)

A
  1. 1/2x

2. 2x

22
Q

How much is 10dB? (2)

A
  1. 1/10x

2. 10x

23
Q

Define decible

A

The ratio between 2 intensities

24
Q

What is the formula for attenuation in normal tissue?

A 
a = ac x L
a = attenuation 
ac = attenuation coefficient 
L = length/distance
25
Q

What is the formula for attenuation coefficient?

A 
ac = 1/2f
ac = attenuation coefficient 
f = frequency
26
Q

Half value layer

A

The thickness of material that will halve the original intensity
- the distance it takes to drop 3dB

Physics 1 (42 decks)

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