Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Ultrasound Physics > Interaction Of Sound And Media > Flashcards

Interaction Of Sound And Media Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
0
Q

What results in increased attenuation?

A

Higher frequency and longer path length. The further ultrasound travels, the more attenuation occurs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

The decrease in intensity, power and amplitude of a soundwave as it travels.

A

Attenuation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What results in less attenuation?

A

Lower frequency and shorter path length. In soft tissue, lower frequency results in less attenuation. Thus, we penetrate further with lower frequency sound.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are three components of attenuation?

A
  1. Absorption – primary, sound converted into heat.
  2. Scattering
  3. Reflection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

A 3 MHz sound beam travels through 2 media. It attenuates 5 dB in medium a and 6 dB in medium be. What is the total attenuation that the sound beam undergoes as it travels through both media?

A

11 dB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

This occurs when propagating sound energy strikes a boundary between two media and some returns to the transducer.

A

Reflection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Reflections from a smooth reflector, like a mirror, are called what?

A

Specular reflections, and they return in one direction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Specular reflectors are well seen when sound strikes the reflector at how what degrees?

A

90°

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What type of reflection occurs when a boundary is rough, and reflected sound is disorganized and random?

A

Diffuse reflection or backscatter, (occurs with blood)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When a reflector is much smaller than the wavelength of sound, sound is uniformly distributed in all directions, or omnidirectional. What is this interaction of sound and media called?

A

Rayleigh scattering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is Rayleigh scattering related to frequency?

A

Rayleigh scattering is related to frequency^4.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Name two organized, systematic interactions between sound and media.

A

Specular reflection

Rayleigh scattering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Name 2 disorganized, chaotic interactions between sound and media.

A

Diffuse reflection

scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is attenuation coefficient?

A

The amount of attenuation per centimeter. A way to report attenuation without dealing with distance. Attenuation coefficient is related frequency.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the units of measurement for attenuation coefficient?

A

Decibels per centimeter

dB/cm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the attenuation coefficient in soft tissue? How is it expressed mathematically?

A

It is approximately one half of the frequency (MHz).

0.5 dB/cm/MHz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the equation for total attenuation?

A

Total attenuation (dB) = path length (cm) x attenuation coefficient (dB/cm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q 
Which of the following is the best estimate for the attenuation coefficient of sound traveling in soft tissues?
A. 1.8 dB/cm/MHz
B. 0.77 dB/cm/MHz
C. 0.45 dB/cm/MHz
D. 1.0 dB/cm/MHz
A

C. .45 dB/cm/MHz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

A calculation of the opposition of the propagation of sound through a given medium.

A

Impedance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the units for impedance?

…and it’s abbreviation?

A

Rayls, often represented by the letter Z.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the typical values for impedance?

A

1,250,000 - 1,750,000 Rayls

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the equation for impedance?

A

Impedance (Rayls) = density (kg/m^3) x propagation speed (m/s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Name the three components of attenuation. Which one is the dominant contributor to attenuation?

A

Absorption, reflection, and scattering. Absorption attenuates sound the most.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

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

A

Increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Total attenuation in soft tissue is related to ______ & ______?

A

Path length and frequency of the sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Is attenuation in lung tissue greater than, less then, or equal to that of soft tissue?

A

Greater than

26
Q

Is attenuation in bone greater than, less than, or equal to that of soft tissue?

A

Greater than

27
Q

Is attenuation in air greater than, less than, or equal to that of soft tissue?

A

Much greater than

28
Q

Is attenuation in water greater than, less then, or equal to that of soft tissue?

A

Much less than

29
Q

What are the units of attenuation?

A

Decibels

30
Q

What is the relationship between propagation speed and the attenuation coefficient in soft tissues?

A

Speed and attenuation coefficient are unrelated.

31
Q

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

A

In soft tissue, the attenuation coefficient in dB/cm is about half of the ultrasonic frequency in megahertz.

32
Q

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

A

Remains the same

33
Q

Acoustic impedance = _____x_____

A

Density (kg/m^3) x propagation speed (m/s)

34
Q

Impedance is important in ______ at boundaries.

A

Reflections

35
Q

Which is better to use while examining a carotid artery, a 7.5 or 3.0 MHz transducer?

A

7.5 MHz transducer is better because the higher frequency transducer produces the better image. We can use the higher frequency transducer because the structure is superficial and attenuation is not a problem.

36
Q

In soft tissue, attenuation coefficient is directly related to ______.

A

Frequency (if frequency doubles, attenuation coefficient will double).

37
Q

Rayleigh scattering is related to _____.

A

Frequency^4

If frequency doubles, Rayleigh scattering increases by a factor of 16. (2x2x2x2=16)

38
Q

What are other names for normal incidence?

A

Perpendicular, orthogonal, right angle, and 90°.

‘PORNN’

39
Q

What is oblique incidence?

A

Anything other than 90°; not at right angles.

40
Q

What are two types of oblique angles?

A

Acute angles, which are less than 90°, and obtuse angles, which are greater than 90°, are oblique.

41
Q

The intensity of the soundwave at the instant prior to striking a boundary.

A

Incident intensity

42
Q

The portion of the incident intensity that, after striking a boundary, changes direction and returns back from where it came.

A

Reflected intensity

43
Q

The portion of the incident intensity that, after striking a boundary, continues on in the same general direction that it was originally traveling.

A

Transmitted intensity

44
Q

Due to the principle of the conservation of energy, what is the equation for incident intensity?

A

Incident intensity = reflected intensity + transmitted intensity

45
Q

What is the intensity reflection coefficient?

A

The percentage of the ultrasound intensity that bounces back when the sound strikes a boundary

46
Q

What is the intensity transmission coefficient?

A

The percentage of the incident intensity that, after striking a boundary, continues on in the same general direction that it was originally traveling.

47
Q

When intensity reflection coefficient and intensity transmission coefficient are added together, what is the result?

A

100%

48
Q

How are coefficients reported?

A

As percentages

49
Q

With normal incidence, reflection occurs only if the two media at the boundary have ________________.

A

Different acoustic impedances

50
Q

Will transmission or reflection occur with oblique incidence?

A

I don’t know! Transmission and reflection may or may not occur with oblique incidence. There are no simple rules to predict if so.

51
Q

With oblique incidence, incident intensity equals what?

A

Incident intensity = transmitted+ reflected

52
Q

With oblique incidence reflection angle equals what?

A

Reflection angle = incident angle

53
Q

What is refraction?

A

Refraction is transmission with a bend.

54
Q

A change in direction as sound transmits from one medium to another

A

What his refraction, Alex?

55
Q

What is required for refraction to occur?

A

We fraction requires both: oblique incidence and different speeds.

56
Q

What law describes the physics of refraction?

A

Snell’s Law

57
Q

Soundwaves strike a boundary at normal incidence. The impedances of the two media are identical. What percentage of the soundwave is refracted?

A

0%, remember refraction requires oblique incidence and different speeds.

58
Q

Which of these media has the greatest attenuation and the slowest speed? Bone, tendon, fat, air?

A

Air

59
Q

Which of these media has the greatest attenuation and the fastest speed? Bone, tendon, lung, fat, air?

A

Bone

60
Q

Which of the following describes the physics of refraction mathematically?
Bernoulli’s principal, Snell’s Law, Pouiseulle’s law, Murphy’s Law, Bernoulli’s law?

A

Snell’s Law

61
Q

Which of the following terms does not belong with the others? Oblique, normal, perpendicular, orthogonal,90°?

A

Oblique

62
Q

Which of the following terms best describes a reflection arising from a rough boundary? Non-diffuse, absolute, Rayleigh, smooth, non-specular?

A

Non-specular

63
Q

A sound wave strikes a boundary between two media with different impedance is. The angle of incidence is non-orthogonal. Which of the following statements is most correct? All of the sound will be reflected. Some of the sound will be reflected. Some of the sound may be reflected. Some of the sound will be refracted. None of the sound will be refracted.

A

Some of the sound may be reflected.

Ultrasound Physics (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions