Bioeffects Flashcards
Small transducer that measures the characteristics of a sound beam. It is similar to a small hypodermic needle with a tiny piece of pieoelectric materal on the end
Hydrophone / microprobe
What proposes that bioeffects result from tissue temperature evaluation
Thermal mechanism
two bioeffect mechanisms
Thermal and cavitation
TIS is
Soft tissue thermal index. Sound traveling in soft tissue
TIB is
Bone thermal index. Assumes that bone is at or near the focus of the sound beam
TIC is
Cranial bone thermal index. Assumes that cranial bone is in the sound beams near field
The study of characteristics, attributes, and quantities of a substance that induces bioeffects is called
Dosimetry
T/F there are no bioeffects in us
False
T/F there are no harmful bioeffects associated with us
True
A combo of __ and __ determine the likelihood of harmful bioeffects
temperature and exposure time
Maximal heating is related to the beams
SPTA intensity
Nonthermal or mechanical mechanisms consist of
Cavitation and radiation force
Two forms of cavitation
Stable and transient
Interaction of sound waves with microscopic gas bubbles in tissues. Also described as the creation of gaseous nuclei from dissolved gases in a fluid
Cavitation
Lower MI levels and do not burst
Stable
Higher MI levels, bubble bursting
Transient
Transient is also called
Normal and inertial cavitation
Stable cavitation have
microstreaming and shear stresses
Lower MI means ___ cavitation, ___ pressure, and ___ frequency
less, less, higher
Which modality is associated with the lowest tissue temp evaluation
Gray scale imaging
Which modality is associated with highest tissue temp evaluation
Pulsed doppler
Which component of an us system is most likely to expose a patient to danger
Transducer
What is an appropriate use of us in ob
Provide medical benefit to the patient
Unfocused or focused sound beams are less likely to create bioeffects because the beam will strike less gas bubbles
Focused
The upper limit for the SPTA inensity of a focused us wave where there have been no observed bioeffects is
1 W/cm2
What is the highest SPTA intensity of an unfocused ultrasound wave where there have been no observed bieffects
100 mW/cm2
What has the highest mechanical index
low frequency, high pressure
What us beam is more likely to cause temp elevation in soft tissue
unfocused
What is considered the most important for a sonographer to decrease the liklihood of bioeffects
Duration of the study
What devices convert us energy into heat
calorimeter and thermocouple
