Exam 3 Flashcards
What is the relationship of the diameter of the transducer and the divergence angle
Inversely related
Large Dia, small angle
Small dia, large angle
High frequency will create a beam with
Deep foci
T or F:
High frequency causes beam to attenuate more
True
Large diameter crystals create beam with ____ (Deep or Shallow) foci
Deeper foci
Pulse waves have _____ pulses and have ____ crystals
Short pulses, 1 crystal
CW waves have _____ waves, and have _____ crystals
Continuous wave, 2 crystals
What are the pros of CW Doppler
Aliasing never happens
What are the cons of CW Doppler
Velocity on entire region overlap between receive and transmit beams (Range ambiguity)
What are the instrument controls for CW
Transmit power control
Receiver sensitivity or gain control
Wall filter control
Equation for PRP
1/PRF
Equation for PRF
1/PRP
What is the equation for PD
1/frequency
How do we steer a beam
Adjust firing times of signal
What is apodization
Strength of side and grating lobes are reduced
What is the main purpose of apodization
To get rid of side and grating lobes
How can apodization be reduced
Sending different electrical spikes to each element
Stronger electrical signals are sent to
Center elements instead of sides
What are side lobes
Additional areas of sound energy equal to and greater than focal zone exist outside of the main beam
Side lobes are known to reduce
Lateral resolution
Side lobes are only located in the
Far field
Side lobes are ___% of the main beam
14%
Side lobes pulse the beam which will
Reduce effects
Side lobes have a single element that produce
Sound continuously
What are grating lobes
Lobes resulting of array transducer scanning
Grating lobes are located only in
Both near and far field
Grating lobes can be reduced by
Making tightly packed array elements
What are the pros of a linear switched array
Wide linear image
What are the cons of linear switched array
Fixed focus
Not able to steer
$$$
Where is linear switched array going to be used
Vascular imaging, Doppler, color Doppler
What is mechanical steering
Motorized dome over top
What are the pros of mechanical steering
Cheap
What are the cons of mechanical steering
Fixed focus
Mechanical wear
Motion
Limited temporal range
Annular array is used in
2-D, M Mode Doppler, and color Doppler
What are the pros of annular array
Variable focus in lateral and elevational resolution
Depth of field
What are the cons of annular array
Mechanical wear
Motion
Temporal resolution
Grating lobes
$$$
When are 1-D phased array sectors used
Used in cardiac imaging
What are the main frequency ranges in 1-D phased array sectors
2-4MHz
What is the peds frequency range in 1-D phased array sectors
5-8MHz
What is the frequency range in small adults and children in 1-D phased array sectors
3.5-5MHz
What are the pros of 1-D phased array sector
Varable focus
Motion artifacts eliminated
Parallel processing is option
What are the cons of 1-D phased array sectors
Relative to mechanical:
Relative to 2-D:
M - $$$, electronics are complicated
2-D - Fixed elevational focus, no elevational dimension
When are 1-D Curved linear arrays
2-D, color Doppler, and Doppler
What are the pros of 1-D Curved linear array
Variable focus in lateral
Wide linear image in near field
Can do parallel processing
What are the cons for 1-D curved linear arrays
Relative to mechanical:
Relative to 2-D:
M - $$$
2-D - Fixed elevation focus, no steering in elevation
2-D arrays can image well in
Both lateral and elevational planes
What are the 3 types of transducer
Linear
Annular
Convex
Active elements in a straight line
Linear
Circle rings
Annular
Elements in arched line
Convex
What is the shape of linear transducer
What will happen when there’s a dropout
Rectangular
1 vertical black line will drop
Annular rings acquire date from
Shallower depths and the outer from deeper depths
What is the shape of annular transducer
What will happen if there’s a dropout
Pie
Dropout makes a ring
In convex array pulses are sent out
Simultaneously but are radial in nature
What is the shape of convex array
What will happen if there’s a dropout
Windshield shape
Dropout will cause 1 black vertical line
What are the 3 methods of focusing
External focusing
Internal focusing
Phased array focusing
External focusing is the use of
Lens
Internal focusing is the use of
Curved active element
Phased array focusing is the use of
Onboard electronics to achieve focus
What is the relationship of PZT thickness and frequency
Inversely related
What is the equation for PZT thickness
Frequency (MHz) = (Speed of sound in PZT (mm/us) / 2 x Thickness (mm)
T or F:
Thickness determines pulse wave and continuous wave
False
Pulse wave only
Thin crystals produce sound pulses with ____ (High or low) frequencies
Higher frequencies
What are the 2 factors that affect NZL
Diameter/apeture of transducer
Frequency of sound produced by transducer
A large diameter and high frequency will give you a ____ foci (Shallow or Deep)
Deep
Small diameter and low frequency will give you a _____ foci (Shallow or deep)
Shallow
What is the matching layer
1/4 of the thickness of matching layer of sound
What is LATA
Lateral, Angular, Transverse, Azimuthal
What is LARRD
Long, Range, Radial, Depth
What are types of flow
Pulsatile
Phasic
Steady
Laminar
Turbulent
Continuity
What is pulsatile flow
What is an example
Variable velocity flow due to cardiac contraction
Ex. Arterial circulation
What is phasic flow
What is an example
Variable velocity due to respiration
Ex. Venous circulation
What is steady flow
What is an example
Constant velocity flow
Ex. When holding one’s breathe
What are the 2 types of laminar flow
Define them
Parabolic - Average flow is 1/2 of the max,
Plug flow - All layers have same speed
What is laminar flow
Layered flow, liquid is at different speeds as youn move from vessel wall
What is turbulent flow
Random/chaotic circles or eddies
What is continuity flow
Volume flow rate must be constant in the before, at, and after
What does continuity flow mean
Blood cannot be created or destroyed as it moves through the vessel
What is the boundary condition
Flow must = 0 at vessel wall
What does FFT cause in laminar flow
Shoots all ticks to final box
What does FFT cause in turbulent flow
Shoots ticks all over in different boxes
FFT results in more
Velocity bins being filled in spectral window (Spectral broadening)
What is PI
What is the equation
What are the units
Pulsatality index
PI = (Max - Min) / Ave
No units
What is the relationship of the sine of an angle and wavelength
Now with frequency and sine of the angle
Inversely related
Inversely related
What is RI
What is the equation
What are the units
Resistivity index
RI = (Max - Min) / Max
No units
Technique that is used to quantify and to image the blood flow, in turn would mean we are checking the hearts motion
Doppler
What is the basic premise of Doppler
Relative motion of sound source and observer
What are the 3 ways to produce Doppler
Sound source moves, listener stays
Sound source stays, listener moves
Sound source and listener move
CW Doppler transmits waves used and receive waves that produce
Product of 2 signals
If you have a large diameter how will that affect your NZL
NZL will increase by same amount
PW Doppler look at
Specific depths (Volume)
In PW Doppler there are more:
Results in:
More cycles in each pulse
Results in improved sensitivity
What is the purpose of the wall filter
Remove low frequency signals
In color Doppler you are no longer looking at the peak amplitude you are looking at
Reflector velocities average
What is used to acquire color Doppler
Multiple pulse echo sequence
In color Doppler if there is a bulid up the signal is going to take____ (More or less) time to be displayed
More
Power Doppler indicates the presence of
Doppler shift
Power Doppler does not look at ____ or ____
Speed or direction
Power Doppler is also known as ____ Mode or color ____
Energy mode or color angio
What are the pros of Power Doppler
Increased sensitivity to low
velocity flow
No aliasing (Velocity is not considered)
Unaffected by Doppler angles but for 90 degrees
What are the cons for Power Doppler
Can’t know direction
Lower frame rates
Susceptible to motion of patient
Aliasing is directly related to
Cuts off
PW Doppler
Peak velocity
Aliasing causes a cut off in ___
Aliasing causes no cut off in ___
PW Doppler
CW Doppler
Color percevied by the viewer
Hue
Hue that is mixed with white
Saturation
Brightness of saturation
Luminance
The less white present the greater the
Saturation
Luminance represents
Echogenicity
Measuring Doppler with frequency within each pixel associated with a pulse pocket
Variance
Variance is used as an effective measure to indicate
Turbulence
Velocity mode for color cannot determine
Laminar or turbulent flow
What does color red mean
Flow toward the transducer
What does color blue mean
Flow away from the transducer
How do you indicate turbulence and laminar flow in color on the screen
Laminar is on left side
Turbulent is on right side
Describe the relationship between period and frequency
Inversely related
What is th equation for period
1/f
What is the equation for frequency
1/P
Name the powers of 10
1,000,000,000
1,000,000
1,000
0.01
0.001
0.000001
0.000000001
10^9 - Giga
10^6 - Mega
10^3 - Kilo
10^-2 - Centi
10^-3 - Milli
10^-6 - Micro
10^-9 - Nano
What is the equation for Nyquist Limit
PRF/2
Name the equations for far field divergence angle
Sin0 = 1.2 x wavelength / Diameter
Sin0 = 1.2 x prop speed / Diameter x Frequency
Name the equations for NZL
Diameter x frequency / 6.16
Diameter^2 x frequency / 6
r^2 / Wavelength
What is the equation for RI and PI
RI = (Max - Min) / Max
PI = (Max - Min) / Ave
What are the equations for Doppler Shift
Doppler shift = Reflected Frequency - Transmitted Frequency
Fd = 2fovcos0 / c
What is Bernoulli’s Equation
Constant = P + 1/2pv^2 + pgh
