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Ultrasound Physics > Ch 24: Bioeffects > Flashcards

Ch 24: Bioeffects Flashcards

1
Q

This is a probe similar to a small hypodermic needle with a tiny piece o PZT attached to its end.

A

hydrophone or microprobe

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2
Q

T/F? Hydrophones measure the pressure of the entire sound beam.

A

FALSE, specific locations within the beam

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3
Q

What does a hydrophone measure?

A

acoustic pressure, period, PRP, PRF, and pulse duration

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4
Q

What does a calibrated hydrophone measure?

A

intensities and output

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5
Q

When is transducer output lowest?

A

gray scale

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6
Q

When is transducer output highest?

A

pulsed Doppler

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7
Q

What do we call the hydrophones made from a very thin layer of PZT plastic?

A

membrane hydrophone

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8
Q

This shadowing system allows us to view the shape of a sound beam in a medium.

A

Schlieren

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9
Q

What three devices measure the output of u/s transducers by absorption?

A
  1. calorimeter
  2. thermocouple
  3. liquid crystal
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10
Q

This measures the total power in a sound beam through the process of absorption.

A

calorimeter

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11
Q

This measures the sound beam at a particular location with a tiny electronic thermometer.

A

thermocouple

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12
Q

This measures the sound beam via thermal energy levels represented by color changes.

A

liquid crystals

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13
Q

A primary mandate regarding clinical u/s is that…

A

benefits to the patient must outweigh the risks.

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14
Q

This is the science of identifying and measuring the characteristics of an u/s beam that are relevant to its potential for producing biological effects.

A

dosimetry

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15
Q

Bioeffects research may be conducted in what two broad areas?

A

in vivo and in vitro

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16
Q

This kind of research is performed within the living body of an animal or plant.

A

in vivo

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17
Q

This kind of research is performed outside the living body in an artificial environment.

A

in vitro

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18
Q

Summary statements from the AIUM statement on in vitro bioeffects are…

A
  1. the research is important
  2. the effect are real (even if they don’t apply to the clinical setting)
  3. be skeptical of any research claiming otherwise
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19
Q

What two techniques can be used to study bioeffects?

A
  1. mechanistic

2. empirical

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20
Q

This research approach searches for a relationship between cause and effect.

A

mechanistic

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21
Q

This research approach searches for a relationship between exposure and response.

A

empirical

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22
Q

In which research approach can a broad exposure range be evaluated?

A

mechanistic

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23
Q

In which research approach is there no need to understand the mechanism?

A

empirical

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24
Q

In which research approach can there be uncertainty about assumptions?

A

mechanistic

25
Q

In which research approach is the biological significance obvious?

A

empirical

26
Q

In which research approach may other mechanisms than the one in question be involved?

A

mechanistic

27
Q

In which research approach may species difference alter results?

A

empirical

28
Q

In which research approach may the bioeffect in study be clinically insignificant?

A

mechanistic

29
Q

Is the mechanistic or empirical research approach better?

A

Neither, but conclusions are strongest when the results from both agree.

30
Q

Two important bioeffects mechanisms are…

A
  1. thermal

2. cavitation (nonthermal)

31
Q

This mechanism proposes that bioeffects result from tissue temperature elevation.

A

thermal

32
Q

This is a useful predictor of maximum temperature increase under most clinically relevant conditions.

A

thermal index (TI)

33
Q

This index assumes that sound is traveling in soft tissue.

A

soft tissue thermal index (TIS)

34
Q

This index assumes that bone is at or near the focus of the sound beam.

A

bone thermal index (TIB)

35
Q

This index assumes that cranial bone is in the sound beam’s near field.

A

cranial bone thermal index (TIC)

36
Q

T/F? Thermal indexes are the best measurements or estimates of in vitro tissue temperature elevation.

A

FALSE, in vivo

37
Q

A combination of __ and __ determine the likelihood of harmful bioeffects.

A

temperature and exposure time

38
Q

Tissue heating is related to the __ of the transducer and the __ of the tissues.

A

output characteristics, properties

39
Q

Which intensity’s rating is the most important in the study of bioeffects?

A

SPTA

40
Q

This mechanism proposes that bioeffects result from cavitation and radiation force.

A

nonthermal (cavitation) or mechanical

41
Q

This is exerted by a sound beam on tissues, creating sheer stresses and streaming fluids that can distort or disturb biological structures.

A

radiation force

42
Q

This is the interaction of sound waves with microscopic, stabilized, gas bubbles in the tissues.

A

cavitation

43
Q

Cavitation bubbles are known as…

A

gaseous nuclei.

44
Q

T/F? Cavitation bubbles are the same as the gas bubbles of contrast agents.

A

FALSE, different

45
Q

The two forms of cavitation are..

A
  1. stable

2. transient

46
Q

In this form of cavitation, the bubbles may double in size but not burst, absorbing acoustic energy and causing microstreaming and sheer stress.

A

stable cavitation

47
Q

In this form of cavitation, the bubbles burst causing colossally increased temperatures and shock waves.

A

transient cavitation

48
Q

T/F? The bioeffects of transient cavitation are very concerning in clinically ultrasound.

A

FALSE, not considered clinically important

49
Q

Stable cavitation is associated with __ MI levels.

A

lower

50
Q

Transient cavitation is associated with __ MI levels.

A

higher

51
Q

Transient cavitation is also known as…

A

inertial or normal cavitation.

52
Q

The likelihood of cavitation bioeffects and higher MI occurs with __ pressure and __ frequency.

A

more, lower

53
Q

This is an empirical branch of medicine associated with population studies and clinical surveys.

A

epidemiology

54
Q

What are the three limitations to epidemiologic studies?

A
  1. retrospective
  2. ambiguous
  3. other risk factors can’t be controlled for
55
Q

The best epidemiologic studies are..

A
  1. prospective

2. randomized

56
Q

These kinds of studies are forward-looking.

A

prospective

57
Q

These kinds of studies create two groups of patients.

A

randomized

58
Q

T/F? It is never appropriate to use diagnostic u/s for entertainment.

A

true

59
Q

T/F? The greatest risk to the patient undergoing ultrasound is yet unknown thermal or mechanical bioeffects.

A

FALSE, electrical shock from a cracked transducer housing

Ultrasound Physics (23 decks)

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