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
what is the image shape of the convex transducer
blunted sector
what shape is the image of a linear phased array
rectangular
what happens when a crystal is damaged in a linear sequential
the image portion below the damaged crystal is lost
when the beam is steered on the linear sequential what happens to the image
it turns into a parallelogram
the curvilinear transducer is also called
convex, curved
how many crystal does the curved transducer have
120 to 250
what happens when a crystal is damaged in the curved transducer
only the portion below the dame is lost
how many crystals are fired in the convex transducer
some but not all
how many crystals are fired in the vector array
some but not all simultaneously
what image shape does the vector array make
trapezoidal
slice thickness is also called
elevational resolution
side lobes are created by
single element transducers
lateral resolution is degraded by
side lobes
what is apodization
the process to get rid of grating lobes by using electrical signals
dynamic aperture is also called
variable aperture
what is variable aperture
a technique used to make a sound beam narrow over a greater range of depth
dynamic aperture improves what resolution
lateral
what is the frame rate determined by
speed in the medium and depth
what is the relationship between frame rate and temporal resolution
directly related
what two system settings determine the frame rate
imaging depth and number of pulses
multi focus does what to temporal resolution
decreases temporal resolution and frame rate
what does line density improve
spatial resolution
What does line density degrade
temporal resolution and frame rate
what are the two major functions of the ultrasound system
prep/transmission and reception
what does the pulser do
determines the amplitude,PRP and PRF by exciting the crystals
what happens when pulser voltage is low
the entire image will be dark
What two measurements are used to standardize output
thermal and mechanical index
what is the most common way to increase signal-to-noise ratio
output power
what does the switch do
protects the receiver components from powerful transmission signals and directs electrical signals from the transducer
order of 5 receiver operations
amplification
compensation
compression
demodulation
reject
what is amplification also known as
receiver gain
what happens during receiver gain
electronic signals are made equally larger
pre amplification happens where
within the transducer
compression is also known as
dynamic range or log compression
what are the two processes of demodulation
rectification and smoothing
what does rectification do
turns negatives voltage into positives
can you adjust demodulation
no
high contrast results in what kind of image
bistable
storage of information in the scan converter is called what
writing
what kind of number am I if I have unlimited choice
continuous values
analog
what scan converter has excellent spatial resolution
analong
what is a pixel
the smallest building block of a digital picture
higher pixel density improves what resolution
spatial
higher pixel density is achieved with
smaller pixels, more pixels per inch
what is a byte
a group of 8 bits
a bit is
the smallest amount of computer memory
if you have more bits you have more
shades of gray
1 bit is how many shades of grey
2
what are the things that happen during preprocessing
compensation
compression
write magnification
compounding
true or false: spatial resolution changes during read magnification
false
coded excitation occurs where
in the pulser
what is spatial compounding
using info from different image angles to produce a single image
compound imaging reduces what artifacts
speckle and shadowing
what are the downsides to spatial compounding
reduced temporal resolution and frame rate
frequency compounding reduces what artifacts
noise and speckle
temporal compounding is also known as
persistence or temporal averaging
true or false temporal resolution works best with slow-moving objects
true
what does PACS stand for
picture archive and communication systems
what does DICOM stand for
digital imaging and computers in medicine
what is dicom
a set of rules that allow imaging systems to share information
what is dynamic range
the extent a signal can vary and still maintain accuracy
dynamic range is measured in
Decibels
what is harmonic imaging
twice the fundamental frequency
what are the two types of harmonics
tissue and contrast
true or false: harmonics only happen at a superficial depth
false harmonics do not happen at all in superficial depth
harmonics increase what
signal to noise ratio
true or false: weak sound beams do not create harmonics
true
harmonics are primarily created where
along the beam’s main axis
what is the disadvantage of pule inversion harmonics
lower temporal resolution/ frame rate
contrast harmonics are created during
reflection
what creates better harmonics high or low frequency
lower frequency
what does the MI need to be to create harmonics what is the best MI
0.1 and above…. above 1 is the best
flow is also called
volume flow rate
what are the three basic forms of blood flow
pulsatile, phasic, steady
pulsatile flow appears in what circulation
arterial or cardiac contraction
phasic flow appears in what circulation
venous
what are the two types of laminar flow
plug flow and parabolic
velocity is highest in the lumen with which flow
parabolic flow
what does the Reynold number predict
whether flow is laminar or turbulent
turbulent flow coverts
flow energy into sound and vibration
the sound associated with turbulent flow is called
murmur or a bruit
in a stenosis where is the pressure lowest
narrowest portion of the stenosis
where is the velocity the highest in a stenosis
the narrowest part of the stenosis
pressure gradient increases when
flow increases or resistance increases
during normal function veins have what kind of pressure
low
supine means
flat on your back
when standing hydrostatic pressure is
zero at heart level only
when lying down hydrostatic pressure is
zero everywhere and is the true circulatory pressure
what is the hydrostatic pressure standing up from the ankles to the head
ankle:100
knees:75
waist:50
chest:0
top of head: -30
during inspiration the diaphragm moves
downward, increasing venous return to the heart
during expiration the diaphragm moves
upward increasing venous flow from the legs
Doppler shift is also called
the doppler frequency
what is demodulation
extracting the low Doppler frequency
The Doppler shift is
a low frequency that rides on top of the transducer frequency
when the blood cells are moving toward the transducer the Doppler shift is
positive
velocity is defined as
magnitude and direction
The Doppler shift is directly related to the
velocity
The x-axis of the Doppler spectrum represents
time
the Y-axis of the Doppler spectrum represent
velocity
you never want your angle to be what degree
90
you always want your angle to be
0 or 180
a 60-degree angle means the velocity measurement is
half
flow above the baseline means
towards the ransducer
continuous wave transducer requires how many crystals
two
what are the disandvanges of CW
the exact location cannot be determined (range ambiguity)
anatomic imaging and doppler is called
duplex imaging
true or false: CW transducers use backing material
false
CW transducers have what bandwith
narrow
what are the disadvantages of PW
inaccurate measurement of high velocity
true or false: aliasing can happen with CW
false
the Nyquist limit is
the highest doppler frequency/ velocity
what are the two ways to avoid aliasing
increase the nyquist limit or reduce the doppler shift
deeper sampler volumes have
a low PRF and low nyquist limit
true of false: higher frequencies create more aliasing
true
what are the 5 techniques to avoid aliasing
adjust scale
shallower view
lower frequency transducer
baseline shift
use CW
grey shades on the doppler are related to
number of blood cells
Color Doppler reports what type of velocity
average or mean velocity
Spectral Doppler reports what type of velocity
peak velocity
variance mode shows what type of flow
turbulent and laminar
the left and right side of variance mode shows what type of flow
left is laminar
right is turbulent
what is an ensemble
multiple pulses on the color doppler
what are the disadvantages of packets
lower frame rate and temporal resolution
power mode is
non directional
power doppler is also called
energy mode or color angio
what are the advantages of using power mode
increased sensitivity to slow flow
unaffected by the angle
no aliasing
what are the disadvantages of energy mode
no velocity measurement
lower frame rate
susceptible to motion
on spectral doppler low-frequency doppler shifts are called
clutter
wall filter is also called
low pass filter
what is cross-talk
a special form of mirroring, the doppler spectrum is shown above and below the baseline
cross-talk results from
the doppler gain is set too high
angle is near 90
what is spectral analysis
a tool that breaks complex signals down
what are the two methods of spectral analysis
fast Fourier transform
autocorrelation
true or false FFT can only be used for PW
false FFT can be used for CW and PW
what is spectral broadening?
a range of velocity shown by the spectral window being filled
autocorrelation is only used with
color doppler
what happens when the color gain is set too high
color confetti
what happens when the color gain is set too low
color disappears
what is isoechoic
structures with equal brightness
how does the artifact reverb appear
resembles a latter, multiples equally spaced
what causes reverb artifact
bouncing of the soundwave between 2 strong reflectors
comet tail artifact is caused by what 2 things
very high propagation speeds or gas bubbles
why does shadowing appear
attenuation is higher in the structures above
shadowing is not related to what
the speed of sound in a medium
focal banding is also called
focal enhancement
with the mirror artifact the artifact is located where
deeper than the real structure
speed error artifact is also called
range error artifact
what is a refraction artifact
when a sound pulse changes direction during transmission
refraction occurs when
a sound wave strikes a boundary obliquely
doppler phantoms contains what 3 things
vibrating string, moving belt, flow fantom
the structures in refraction artifact appear
side by side
sensitivity refers to
the system’s ability to display low level echos
what are the two forms of sensitivity
normal and maximum
what 3 things are adjusted to establish normal sensitivity
output power, amplification, TGC
what kind of dead zone do higher frequency transducers have
thinner
what does a deep dead zone indicate
detached backing, cracked crystal, longer pulse duration
where does the hydrophone measure
a specific location within the sound beam
the hydrophone is also called
micro probe
what is a schlieren
a shadowing system that has to do with acousto optics
what are the 3 devices that measure output of the transducer
calorimeter
thermocouple
liquid crystal
calorimeter measures
the total power of the beam
thermocouple measures
power at a specific location in the sound beam
what is dosimetry
measuring characteristics of an ultrasound beam to its potential for bioeffects
what are the two approaches to studying bioeffects
mechanical and empirical
what does the mechanical approach search for
a relationship between cause and effect
what does the empirical approach search for
a relationship between exposure and response
what are the two bio-effect mechanisms
thermal and cavitation
what is radiation force
sheer stressors and streaming of fluids
what is cavitation
interaction of sound waves on with gasbubbles in tissues
what are the two forms of cavitation
stable and transient
microstreaming and sheer stressors happen during what type of cavitation
stable
transient cavitation is also called
normal or inertial
what are the violent effects of transient cavitation
colossal temps and enormous pressures
what is sensitivity vs specificity
sensitivity is the ability of a test to identify people with a disease
specificity is the ability of a test to identify people without the disease
