Ch. 24 Physics Flashcards
What are the two types of bioeffects
thermal, cavitation
Instrument that can measure the acoustic pressure and the sound beams shape
hydrophone AKA microprobe
What can a hydrophone measure
period, PRP, PRF, PD
Measures force the sound beam creates on any target it comes in contact with
radiation force
Based on the interaction of sound and light
acousto-optics
A shadowing system called a ______ allows us to view the shape of the sound beam in a medium
schlieren
What are the 3 devices that measure the output of the ultrasound transducer by absorption (conversion of sound energy into heat)
calorimeter, thermocouple, liquid crystals
Measures the total power in the entire sound beam through the process of absorption
calorimeter
Calculates the temp rise related to the power of the sound beam at specific locations
thermocouple
Crystals that change color based on their temp
liquid crystals
A primary mandate regarding clinical ultrasound is that the benefit to the patient must outweigh the risk of the exam
risk-benefit relationship
The science of identifying and measuring the characteristics of an ultrasound beam that are relevant to its potential for producing biological effects
dosimetry
Research performed within the living body
in vivo
Research performed outside the living body
in vitro
2 techniques used to syudy bioeffects
mechanistic approach, empirical approach
Begins as a proposal that a specific mechanism has the potential to produce bioeffects (CAUSE AND EFFECT)
mechanistic approach
Based on the acquisition and review of information from patients exposed to ultrasound (EXPOSURE AND RESPONSE)
empirical approach
Mechanism proposes that bioeffects result from tissue temperature elevation
thermal
Predictor of maximum temperature increase under most clinically relevant conditions
thermal index
Thermal index is reported in what three ways
TIS, TIB, TIC
Soft tissue thermal index
TIS
Bone thermal index
TIB
Cranial bone thermal index
TIC
What absorbs more acoustic energy that soft tissue
bone
Maximal heating is related to the beams _____ intensity
SPTA
FDA regulator limit is
720W/cm^2
Temperature elevation becomes progressively _____ from gray scale imaging to color doppler to spectral doppler
greater
Non thermal consists of
radiation force and cavitation
Exerted by a sound beam on tissues. Sheer stresses and streaming fluids can distort or disturb biologic structure
radiation force
Interaction of sound waves with microscopic, stabilized, gas bubbles (gaseous nuclei) in the tissues
cavitation
Occurs at lower mechanical index levels
stable cavitation
With stable cavitation, gaseous nuclei tend to
oscillate (expand and contract)
May occur at higher MI levels
transient cavitation
Transient cavitation is
bubble bursting
Transient cavitation produces what highly localized violent effects
colossal temperatures, shock waves
Calculated number related to the likelihood of harmful bioeffects from cavitation
mechanical index
What two sound wave characteristics is MI related to
peak rarefaction pressure, lower frequency
Branch of medicine associated with population studied
epidemiology
Best epidemiologic studied are
prospective, randomized
Looking forward, protocol is established and specific information is systematically obtained
prospective
One group exposed to ultrasound but not the other group
randomized
AIUM conclusions
the benefit to the patient outweighs the risk, it is inappropriate to use diagnostic ultrasound in a non medical setting for entertainment
