# Week 4 - Attenuation Flashcards

1
Q

As a sound wave travels through tissue, it ___________.

A

Weakens

2
Q

The deeper a sound wave propagates, it loses more and more _____________________.

A

Amplitude, power, intensity (Energy)

3
Q

Attenuation depends on what 3 things?

A

Distance, frequency, and the media

4
Q

Relation. Frequency and Attenuation.

A

Directly

5
Q

Relation. Distance and Attenuation.

A

Directly

6
Q

Attenuation is always measured in _______.

A

-dB (loss of energy)

7
Q

What are the three sources of Attenuation?

A
1. Reflection
2. Scattering
3. Absorption
8
Q

What is the most important source of attenuation?

A

Absorption

9
Q

T/F. Absorption is in the form of interference waves propagating outward and you can feel it happen internally.

A

False. Not even close. Absorption is in the form of HEAT. And you cannot feel it.

10
Q
```Which depth would show the greatest amount of attenuation?
A. 10 mm
B. 1.2 cm
C. 0.05 m
D. 4 cm```
A

C. 0.05 m = 5cm

11
Q

What is the attenuation coefficient range for soft tissue?

A

0.5 to 1 dB/cm for a 1MHz probe

12
Q

State the equation for Attenuation.

A

Attenuation = Attenuation Coefficient x Distance x Frequency

13
Q

What is enhancement caused by?

A

Lower C in fluids causing less attenuation

14
Q

Penetration improves with _________.

A

a lower frequency probe

15
Q

Resolution improves with ___________.

A

a high frequency probe

16
Q

The greatest component of Attenuation is ________.

A

Absorption

17
Q

The Attenuation coefficient in soft tissue = _________.

A

1/2 Frequency

18
Q

More Energy is lost from _______ frequency sound than _______ frequency sound.

A

high, low

19
Q

Half-Value layer thickness = _____________.

A

distance that reduces the intensity by 1/2
OR
the depth that results in 3dB of attenuation

20
Q

The attenuation of Air is _____________.

A

Very High due to absorption and scattering

21
Q

The attenuation of Bone is _________________.

A

Very High due to high absorption.

22
Q
```Which of the following transducers would be the best choice for scanning the greater saphenous vein?
Why?
a. 2 MHz
b. 5 MHz
c. 7 MHz
d. 10 MHz```
A

d. 10 MHz, the GSV is not a very deep structure, therefore a higher frequency would create the best image.

23
Q

What is the term used to describe the brighter echoes deep to a liquid mass compared to adjacent tissues?

A

Enhancement

24
Q

Why are the echoes deep to a fluid filled structure brighter?

A

The fluid has less attenuation than the adjacent tissues

25
Q

Name the three components of attenuation.

A

Absorption, reflection, and scattering

26
Q

As the path length increases, the attenuation of ultrasound in soft tissue ____________.

A

increases

27
Q

Attenuation in lung tissue is ____________ the attenuation in soft tissue.

A

greater than

28
Q

Attenuation in bone is __________ the attenuation in soft tissue.

A

greater than

29
Q

Attenuation in air is _____________ the attenuation in soft tissue.

A

greater than

30
Q

What are the units of attenuation?

A

dB (decibels)

31
Q

T/F. In a given medium, attenuation is unrelated to the speed of sound.

A

True. Attenuation and propagation speed are unrelated.

32
Q

What is the relationship between ultrasound frequency and the attenuation coefficient in soft tissue?

A

the attenuation coefficient in soft issue is approximately 1/2 the frequency.

33
Q

What are the units of the half-value layer thickness?

A

distance (cm)

34
Q

As frequency decreases, depth of penetration _________.

A

increases

35
Q

As path length increases, the half boundary layer _________.

A

remains the same

36
Q

As the path length increases, the attenuation coefficient of ultrasound in soft tissue ________.

A

remains the same