Brainscape's Knowledge GenomeTM

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


See full index

Ultrasound Physics > Bioeffects > Flashcards

Bioeffects Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

Acoustic Variable

A

Pressure, Temperature, particle displacement, density

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

Attenuation

A

sound is absorbed by tissue (heat), non-linear frequency dependent absorption

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

Pulsed Wave Operation

A

Scanned vs non-scanned modality (M-mode vs B-mode)

Duty factor, frame rates

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

Transudcers

A

Focal point of beam, highest intensity,

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

System Operation

A

Output power, SNR

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

Doppler

A

Spectral Doppler and Continuous Doppler

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

Contributions to Bioeffects

A

Heating and Cavitation Mechanisms

Epidemiologic studies in human beings

Observation based research in cells, cultures, plants, and experimental animal studies.

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

Studies for bioeffects

A

Begin at the cellular level which provides information on interaction of mechanisms to guide

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

In animal studies…..

A

Information on thermal and non-thermal bio effects is provided

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

In epidemiology studies…..

A

Long term effects on patients with a history of previous ultrasound examinations are studied

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

Bioeffect

A

Refers to an undesired biological change to tissues as a result of interaction with the insonating beam

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

Sound beam is a

A

Transportation of energy

Energy is work with the possibility of work performed within the body can indicate a potential of adverse biological situations

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

Mechanisms of bioeffects

A

Thermal

Mechanical

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

What are the two principle mechanisms for bioeffects

A

Thermal effects

Mechanical bioeffects

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

Thermal bioeffects

A 
Temperature rise related to: 
temporal average intensity
 duty factor
 scan time
 scanned vs. non-scanned modalities
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

mechanical bioeffects

A

Cavitation related to :

peak rarefactional pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What occurs with thermal bioeffects

A

Temperature in a region rises too high metabolic breakdown occurs and cellular damage can occur

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

What occurs with Mechanical bioeffects

A

Risk involves mechanical damage from interaction between the wave and the tissues within the body

This should not be surprising since sound is a mechanical wave

19
Q

What are possible forms of mechanical bioeffects

A

Inertial / Transient Cavitation

Stable Cavitation

Radiation Force

20
Q

Cavitation

A

Hollow space

21
Q

Cavitation is when….

A

Bubbles are produced, vibrate or oscillate; bubbles burst or implode and a potential for biological effects is present

22
Q

Stable Cavitation

A
  • When oscillation of the microbubbles does not lead to collapse
  • Bubbles oscillate with the varying acoustic pressure field in a stable manner
  • Fluids surrounding the bubbles may begin to flow or stream
  • Flow is the result of eddy currents which develop as energy is imparted to the fluid through the oscillating bubbles
  • Referred to as micro-streaming
  • Momentum of flow is potentially capable of inducing cellular wall stresses that can cause cellular harm
23
Q

Inertial/Transient Cavitation

A

Unlike stable cavitation, this results in implosion of the microbubbles
The microbubbles may completely fragment or the ‘destruction’ may lead to a collection of smaller microbubbles
The likelihood of implosion is related to the peak rarefactional pressure
During this rarefaction phase, the pressure within the bubble relative to the lower decreasing pressure external to the bubble causes the bubble to expand
Clearly during the compression, the increasing external pressure causes the bubble to contract
With increasing ‘negative’ pressure of rarefaction, the bubble expands more and more

24
Q

Inertial Transient Cavitation (Con’t)

A

Eventually the bubble expands so much that when compression begins, there is so much inertia from the surrounding fluid, that the bubble collapses inwardly (implodes)
This collapse can be extremely violent generating high amplitude shock waves and producing extremely high temperatures (as high as 10,000 Kelvin)
These shock waves and localized high temporature increases can cause damage to surrounding regions

25
Q

Inertial Transient Cavitation Con’t 2

A

This can lead to cellular death
Fortunately the affected region is small, potentially only a few cells
The term transient is also used synonymously with the term inertial cavitation
The term transient is indicative of the fact that there is a change in “state” of the bubble
The word inertial is indicative of the fact that the dramatic change in state is the result of inertia

26
Q

Radiation force

A

Is the force exerted by a sound beam on an absorber or a reflector

This force cab deform or disrupt structures

Can cause flow in an absorbing fluid

This flow can cause shear stresses that can deform or disrupt structures

Noncavitational mechanical interaction

27
Q

Radiation force or direct force

A

is the interaction force of an ultrasound beam on an absorber or a reflector.
Basically when the ultrasound wave propagates through the medium it interacts between particles in the tissues
Target particles are pushed away from the transducer which causes acoustic streaming
This produces shear stresses that can disrupt or deform structures

28
Q

Threshold Effect

A

limit or boundary

It implies that there is a limit above which a specific outcome is achieved, and below which a different outcome is occurs

29
Q

Threshold effect-bioeffects

A

threshold bioeffects will force different behaviour and protocols than non-threshold effects

30
Q

cavitation is stable up to…

A

A certain threshold, above which inertial cavitation occur

31
Q

Long periods of time at lower refratctional pressures

A

will not produce inertial cavitation

32
Q

There is no specific point…

A

at which a slight increase in power or scan duration will cause a dramatic increase in tissue temperature
Instead, the temperature change tends to be gradual over periods of time
This behavior is in stark contrast to the threshold behavior of cavitation

33
Q

Mechanical bioeffects ehixibit

A

Threshold behaviour

34
Q

What are mechanical bioeffects are related to ?

A

short-term event during the transmit burst and are not related to longer periods of time

35
Q

Intensity

A

Power/Area

36
Q

What is used to measure the risk of bioeffects

A

Common intensities

37
Q

Common intensities: Concept 1

A

A peak is always greater than or equal to an average

38
Q

Therefore an…..

A

SP is greater than an SA and

a TP is greater than a TA.

39
Q

Common intensities: Concept 2

A

The first letter (S) refers to how the beam is distributed over physical space

40
Q

Common Intensities: Concept 3

A

Pulse measurements

41
Q

Common intensities: Concept 4

A

Temporal (PRP) measuremnts

42
Q

Spatial Distribution

A

Refers to how the beam energy is distributed over physical space in the body.
The beam parameters principally determine the spatial distribution of the beam.

43
Q

Temporal Distribution

A

Refers to how the energy is distributed over time.

Ultrasound Physics (10 decks)

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