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a small hypodermic needle with a tiny piece of piezoelectric material attacfhed to its end. a wire connects the PZT crystal to an oscilloscope
a hydrophone voltage relates to ______ of the sound beam
hydrophones measure accoustic pressure at _____ _______ with the sound beam
by moving the hydrophone to many locations one can determine the sound beams what?
What ultrasound variables can be determined by a hydrophone?
period, PRP, PRF, pulse duration
What output measurements and relationships can be determined by a calibrated hydrophone?
- acoustic pressure vs pressure created
what is the special quality of the hydrophone that is constructed from a very thin membrane of PZT plastic?
it is pressure sensitive
what is the measurable force created by transducers that relates to the power of a beam
a shadowing system that allows us to view the shape of a sound beam in a medium
the conversion of sound energy to heat
3 devices used to measure heat in US
- liquid crystals
measures the total power in a sound beam through absorption
a tiny electronic thermometer it is inserted into the sound beam and the temperature is measured at a particular location. the temp rise is related to the sound beams power
difference between calorimeter and a thermocouple
- calorimeter measures the power of the entire beam
- thermocouple measures a particular location of the beam
this provides insight into the shape and strength of a sound beam by changing color with temperature fluctuations
type of relationship where the benefits must outweigh the risks
the science of identifying and measuring the characteristics of an US beam that are relevant to its potential for producing biological effects
bioeffects research may be conducted in two broad areas
performed within the living body
performed outside the living body
AIUM stands for
American Institute of Ultrasound in Medicine
Summary of AIUM in vitro bioeffects
- in vitro bioeffects research is important
- in vitro bioeffects are real even though they don't apply in the clinical setting
- in vitro bioeffects which claim direct clinical significance (without in vivo validation) should be viewed with caution
two techniques used to study bioeffects
- mechanistic approach
- empirical approach
begins as a proposal that a specific mechanism has the potential to produce bioeffects. based on that proposal, a theoretical analysisis performed to estimate the scope of the bioeffects at various exposure levels
which technique for studying bioeffects is concerned with cause and effect?
based on the acquisition and review of information from patients or animals exposed to ultrasound. seeks relationship between exposure and response
2 important bioeffects mechanisms
proposes that bioeffects result from tissue temperature elevation
a calculated number, it is a useful predictor of max temp increase under most clinically relevant conditions
thermal index TI
TIS stands for
thermal index in soft tissue
TIB stands for
Thermal index in bone
TIC stands for
thermal index in cranial bone
does the thermal index have units
what temperature elevation would cause infertility in the testicles
2 to 4 degrees celcius
no confirmed bioeffects have been confirmed for temperatures up to ___C for exposures less than 50 hours
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