Ch 24: Bioeffects Flashcards
This is a probe similar to a small hypodermic needle with a tiny piece o PZT attached to its end.
hydrophone or microprobe
T/F? Hydrophones measure the pressure of the entire sound beam.
FALSE, specific locations within the beam
What does a hydrophone measure?
acoustic pressure, period, PRP, PRF, and pulse duration
What does a calibrated hydrophone measure?
intensities and output
When is transducer output lowest?
gray scale
When is transducer output highest?
pulsed Doppler
What do we call the hydrophones made from a very thin layer of PZT plastic?
membrane hydrophone
This shadowing system allows us to view the shape of a sound beam in a medium.
Schlieren
What three devices measure the output of u/s transducers by absorption?
- calorimeter
- thermocouple
- liquid crystal
This measures the total power in a sound beam through the process of absorption.
calorimeter
This measures the sound beam at a particular location with a tiny electronic thermometer.
thermocouple
This measures the sound beam via thermal energy levels represented by color changes.
liquid crystals
A primary mandate regarding clinical u/s is that…
benefits to the patient must outweigh the risks.
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.
dosimetry
Bioeffects research may be conducted in what two broad areas?
in vivo and in vitro
This kind of research is performed within the living body of an animal or plant.
in vivo
This kind of research is performed outside the living body in an artificial environment.
in vitro
Summary statements from the AIUM statement on in vitro bioeffects are…
- the research is important
- the effect are real (even if they don’t apply to the clinical setting)
- be skeptical of any research claiming otherwise
What two techniques can be used to study bioeffects?
- mechanistic
2. empirical
This research approach searches for a relationship between cause and effect.
mechanistic
This research approach searches for a relationship between exposure and response.
empirical
In which research approach can a broad exposure range be evaluated?
mechanistic
In which research approach is there no need to understand the mechanism?
empirical
In which research approach can there be uncertainty about assumptions?
mechanistic
In which research approach is the biological significance obvious?
empirical
In which research approach may other mechanisms than the one in question be involved?
mechanistic
In which research approach may species difference alter results?
empirical
In which research approach may the bioeffect in study be clinically insignificant?
mechanistic
Is the mechanistic or empirical research approach better?
Neither, but conclusions are strongest when the results from both agree.
Two important bioeffects mechanisms are…
- thermal
2. cavitation (nonthermal)
This mechanism proposes that bioeffects result from tissue temperature elevation.
thermal
This is a useful predictor of maximum temperature increase under most clinically relevant conditions.
thermal index (TI)
This index assumes that sound is traveling in soft tissue.
soft tissue thermal index (TIS)
This index assumes that bone is at or near the focus of the sound beam.
bone thermal index (TIB)
This index assumes that cranial bone is in the sound beam’s near field.
cranial bone thermal index (TIC)
T/F? Thermal indexes are the best measurements or estimates of in vitro tissue temperature elevation.
FALSE, in vivo
A combination of __ and __ determine the likelihood of harmful bioeffects.
temperature and exposure time
Tissue heating is related to the __ of the transducer and the __ of the tissues.
output characteristics, properties
Which intensity’s rating is the most important in the study of bioeffects?
SPTA
This mechanism proposes that bioeffects result from cavitation and radiation force.
nonthermal (cavitation) or mechanical
This is exerted by a sound beam on tissues, creating sheer stresses and streaming fluids that can distort or disturb biological structures.
radiation force
This is the interaction of sound waves with microscopic, stabilized, gas bubbles in the tissues.
cavitation
Cavitation bubbles are known as…
gaseous nuclei.
T/F? Cavitation bubbles are the same as the gas bubbles of contrast agents.
FALSE, different
The two forms of cavitation are..
- stable
2. transient
In this form of cavitation, the bubbles may double in size but not burst, absorbing acoustic energy and causing microstreaming and sheer stress.
stable cavitation
In this form of cavitation, the bubbles burst causing colossally increased temperatures and shock waves.
transient cavitation
T/F? The bioeffects of transient cavitation are very concerning in clinically ultrasound.
FALSE, not considered clinically important
Stable cavitation is associated with __ MI levels.
lower
Transient cavitation is associated with __ MI levels.
higher
Transient cavitation is also known as…
inertial or normal cavitation.
The likelihood of cavitation bioeffects and higher MI occurs with __ pressure and __ frequency.
more, lower
This is an empirical branch of medicine associated with population studies and clinical surveys.
epidemiology
What are the three limitations to epidemiologic studies?
- retrospective
- ambiguous
- other risk factors can’t be controlled for
The best epidemiologic studies are..
- prospective
2. randomized
These kinds of studies are forward-looking.
prospective
These kinds of studies create two groups of patients.
randomized
T/F? It is never appropriate to use diagnostic u/s for entertainment.
true
T/F? The greatest risk to the patient undergoing ultrasound is yet unknown thermal or mechanical bioeffects.
FALSE, electrical shock from a cracked transducer housing
