Lesson 7

Question 1

What 3 things make up attenuation?

Answer 1

1. Absorption
2. Reflection
3. Scattering

Question 2

Attenuation

Answer 2

Weakening of sound

Question 3

What is the result of weaker signals?

Answer 3

Weaker echoes

Question 4

What structures produce weaker signals?

Answer 4

Structures that are farther away

Question 5

Where is the near field?

Answer 5

Closest are to the transducer

Question 6

Where is the mid field?

Answer 6

Between the near field and the far field

Question 7

Where is the far field?

Answer 7

Farthest area to the transducer

Question 8

What happens to sound as it goes through a medium?

Answer 8

It gets weaker

- has to go through and come back

Question 9

What do we use that can fix attenuation?

Answer 9

TGC

Question 10

What does TGC stand for?

Answer 10

Time gain compensation

Question 11

Whats another word for TGC?

Answer 11

DGC

Question 12

What does DGC stand for?

Answer 12

Depth gain compensation

Question 13

What does the TGC slope provide?

Answer 13

Amplification of specific field echoes

Question 14

What does TGC do?

Answer 14

It amplifies the far field to promote uniform in tissues

- eg) liver

Question 15

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

Answer 15

You are getting equal amounts of amplification

Question 16

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

Answer 16

You get amplification in different spots

- leads to a more uniform image

Question 17

What is the formula for attenuation in soft tissues?

Answer 17

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

Question 18

How does attenuation occur in soft tissues?

Answer 18

0. 5 there and 0.5 back = 1
   - dB/cm x MHz
   - compensates for both directions

Question 19

What 2 things does overall gain do?

Answer 19

1. Amplification of entire field of view

2. Amplification of all incoming echo voltages

Question 20

What is attenuation’s unit?

Answer 20

Decible

- dB

Question 21

How much is 3db? (2)

Answer 21

1. 1/2x

2. 2x

Question 22

How much is 10dB? (2)

Answer 22

1. 1/10x

2. 10x

Question 23

Define decible

Answer 23

The ratio between 2 intensities

Question 24

What is the formula for attenuation in normal tissue?

Answer 24

a = ac x L
a = attenuation 
ac = attenuation coefficient 
L = length/distance

Question 25

What is the formula for attenuation coefficient?

Answer 25

ac = 1/2f
ac = attenuation coefficient 
f = frequency

Question 26

Half value layer

Answer 26

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