SPI Review Flashcards
what is the effect of the medium upon the sound wave called
acoustic propagation properties
what are the 3 acoustic variables
Pressure, density, distance
what are the units of density
KG/cm^3
period is determined by the
sound source only
period is the
time it takes a wave to vibrate a single cycle
frequency is determined by the
source only
what is the frequency of ultrasound
greater than 20 thousand hertz
period and frequency relationship?
inverse
what are the 3 bigness parameters
amplitude, intensity, power
all the bigness parameters are determined by the
sound source
power has units of
watts
power =
amplitude squared
units of intensity
W/cm^2
wavelength is determined by
the sound source and the medium
is the wavelength adjustable
no
what is the relationship between wavelength and frequency
inversely
speed of sound fastest to slowest
solids, liquids, gas
what two characteristics affect the speed of sound
stiffness and density
what other terms describe stiffness
bulk modulus, elasticity, compressability
units of pulse duration
microseconds
pulse duration is determined by
sound source only
pulse length is determined by
source and the medium
is pulse length adjustable
no
is pulse duration adjustable
no
PRP relationship to the period
unrelated
PRP is determined by the
depth and source
PRP and depth are
directly related
PRF is determined by
sound source only
PRF and depth are
inversely related
PRF and frequency are
unrelated
duty factor and depth are
inversely related
depth affects the
PRF,PRF and duty factor
the diffrent measurments of intensity are important in the study of
bioeffects
which intensity is most relevant in respect to tissue heating
SPTA
what is the units for all intensities
W/CM^2
what intensity has the highest value what has the lowest
highest= SPTP lowest=SATA
when intesity is half we have lost
3 decibels
what determines attenuation
path length, frequency
frequency and attenuation are
directly related
what 3 processes contribute to attenuation
reflection, scattering,absorption
diffuse reflection is also called
backscatter
sound back to the transducer organized and disorganized
organized = specular disorganized = diffuse/backscatter
sound in all directions organized and disorganized
organized = rayleigh scatter disorganized = scattering
half-value layer thickness is also known as
penetration depth, depth of penetration, half boundary layer
thin half value =
high frequency/ high attenuation rate
impedance uses units of
rayls or Z
normal incidence is also called
Perpendicular
Orthogonal
Righ angle
Ninty degrees
reflection will only occur if media on either side have
different impedences
how can we predict reflection with oblique incidence
we cannot
refraction is
transmission with a bend
refraction only occurs if
there is oblique incidence and difference propagation speeds with the two media
time of flight is directly related to
the depth
in 1 second sound can travel how many Cm
77,000 cm
the matching layer and gel help
increase the efficiency of sound transfer between the PZT and the skin
decreasing order of impedence
PZT>matching layer>gel>skin
the matching layer is how thick compared to the wavelength
1/4 wavelegth thick
the active element is how thick compared to the wavelength
1/2 the wavelength thick
what are the 3 consequences of using the backing material
decreased sensitivity, wide bandwidth, low Q factor
long pulses degrade what resolution
axial resolution
what is polarization
exposing PZT to electrical field while being heated
the temperature when the PZT is polarized is called
Currie point
how do we sterilize our transducers
we cannot apply heat to them so only disinfection is possible
relationship between PZT thickness and frequency
inversely related
at the starting point, the beam width is
the same as the transducer diameter
the focus is the point where the beam is
the narrowest
the width of the sound beam at the focus is
1/2 the diameter
focal length is also called the
focal depth or near zone length
the focal zone is from where to where
transducer to the focus
what happens to the beam in the far zone
it diverges
at a depth of two near zone lengths, how wide is the beam
same as the active element
with a fixed-focus transducer what two factors determine focal depth
transducer diameter, frequency of the sound
a larger diameter makes what kind of focus
deeper
relationship of transducer diameter and focal depth
directly related
higher frequency makes what kind of focus
deeper focus
smaller diameter crystals create beams that diverge more or less
more divergence
crystal diameter and beam divergence relationship
inversely related
larger diameter crystals improve what resolution in the far field
lateral
frequency and beam divergence relationship
inverse
higher frequency has more or less divergence
less
v shapes waves are known as
spherical waves,diffraction patterns, Huygens wavelets
axial resolution uses the mnemonic
LARRD
Axial resolution is also known as
Longitudinal
Axial
Radial
Range
Depth
Axial resolution is determined by
the spatial pulse length
How is a shorter pulse created
less ringing, higher frequency
lateral resolution is determined by the
width of the sound beam
the mnemonic for lateral resolution is
LATA
Lateral resolution is also known as
Lateral
Angular
Transverse
Azimuthal
lateral resolution is best at what portion of the sound beam
the focus, the narrowest portion
what resolution is better for clinical imaging
Axial resolution
lateral resolution only improves the what field
far feild
fixed focusing is also called
mechanical or conventional
the X-axis of amplitude mode represent
Depth
the Y-axis of amplitude mode represents
amplitude
the X-axis of brightness mode represents
Depth
the Y- axis of brightness mode reresents
Nothing there is no Y axis in B-mode
What axis represents Amplitude in B-mode
Z-axis
the X-axis in M mode represents
Time
the Y- axis in M mode represents
Depth
mechanical transducers contain what type of element
singular, disc-shaped
what image shape does a mechanical transducer create
fan or sector-shaped
what type of steering/focusing does a mechanical transducer use
mechanical steering/ focusing
what are the 3 types of array transducers
linear,annular,convex
how many crystals does a liner phase have
100-300
what image shape does the linear phased create?
fan or sector
what type of steering/focusing does a linear phased have
electronic
what happens when a crystal gets damaged in a mechanical transducer
the entire image is lost
what happens when a crystal is damaged in a linear phased array
erratic beam steering/ focusing
how many elements are fired in a linear phased to create a single sound pulse
all
the beam former is
what creates the different electrical patterns to steer/focus the beam
if the spike pattern is in a straight line that means the beam is
unfocused
a servere curve of the sound beam means the focus is
shallower
annular phased array has what kind of steering
mechanical steering
what happens when a crystal is damaged in a annular phased array
horizontal band of drop out
the linear sequential has how many crystals
120 to 250
the linear sequential array is also called
linear switched array