Chapter 11 & 24 Flashcards
Axis
X=depth
Y=Amplitude
A-mode
Axis
X=depth
Z=amplitude (brightness of dot along beam)
B-mode
Axis
X=time
Y=depth
M-mode
What is the only display mode that provides informatoin regarding reflector otion with respect to time?
M-mode
wiht A-mode, what is displayed on the X-axis
depth of reflector
With M-mode, what is displayed on the y-axis
depth of reflector
which mode provides the foundation for real-time, gray scale autonomic imaging
B-mode
brightness mode
with A-mode, what is displayed on the y-axis
amplitude of the reflected signal
in M-mode, what is displayed on the x-axis
time
with B-mode, which axis is related to the strength of the reflection
Z-axis is related to strength in B-mode
small probe with PZT that measures the acoustic pressure of a sound wave
hydrophone
microprobe
sound beams force upon an object when it strikes it
radiation force
based on the interaction of light and sound
shadowing system call a Schlieren, allows us to view the shape of a sound beam in a medium
acousto-optics
calorimeter
thermocouple
liquid crystal
diveces that measure output of ultrasound transducers by absorption
conversion of sound energy into heat
measures total power in sound beam through process of absorption
energy is transformed into heat
calorimeter
tiny device that measures the temperature rise or fall in a sound beam
thermocouple
they change color based on their temperature
liquid crystals
when do we perform an ultrasound
when the benefits outweigh the risk
science of identifying and measuring the characteristics of an ultrasound beam that are relevant to its potentioal for producing biological effects
dosimetry
research out of the body
In vitro
research in the body
In vivo
mechanistic
empirical
two approaches to study bioeffects
cause and effect
mechanistic
exposure and response
empirical
broad exposure range can be evaluated
strength of mechanistic
uncertainty about assumptions
are other mechanisms involved
is the bioeffect clinically significant
weakness of mechanistic
biological significance is obvious
no need to understand mechanism
strength of empirical
specis differences may alter results
no need to understand mechanism
weakness of empirical
thermal
cavitation (non-thermal)
mechanisms of bioeffects
bioeffects results from the rise in tissue temperature
thermal mechanism
useful predictor of max temperature increase under most clinally relevant conditions
Thermal Index
TI
TIS
TIB
TIC
three forms of Thermal Index
index in soft tissue
TIS
index in bone
TIB
index at cranial bone
TIC
location of highest risk of thermal bioeffects
junction of soft tissue and bone
maximum beam heating related to the
SPTA
testicular temperature rise that can cause infertility
2-4 deg
2 elements of thermal bioeffect measurement
temperature
exposure time
cavitation
radiatoin force
nonthermal mechanisms
interaction of sound waves with microscopic , stabilized gas bubbles in tissue
cavitation
stable
transient
forms of cavitation
oscillating bubble
microstreaming and shear stresses
lower MI
stable cavitation
normal or inertial
bursting bubble
shock waves and very high temperatures
higher MI
transient cavitation
less cavitation
less pressure
higher freq
lower MI
more cavitation
more pressure
lower freq
higher MI
studies associated with population
epidemiology
studies are retrospective
ambiguities in the data
risk factors other than exposure may exist
limitations of epidemiologic studies
prospective
randomized studies
best epidemiologic studies
forward looking study
prospective
one group is exposed and another is not
randomized study
AIUM limit
100mw/cm^2
unfocused beam strength
AIUM limit
1 w/cm^2
focused beam strength
