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156 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Pulser
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controls electric signal sent to the probe
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master synchronizer and Beam former
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coordinates action of all components in time
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Receiver
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produces picture based on electrical signal from the probe
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Scan Converter
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stores analog or digital images
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Beam former: defined
2 thing |
both transmit and receive:
: the appropriate phase delay for focusing and steering :pulse sequencing |
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Apodization: defined
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controls which elements are active or which are not, which is part of Beam Former
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Pulser Modes:
2 kinds |
CW: continuous electrical that is converted into continuous wave
PW: pulser creates an electrical SPIKE and transducer converts it to a pulse |
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SPIKES: actions
What does it control? 5 of them |
each crystal creates its own spike: many spikes for one pulse:
1. Steering(linear steering) 2. focus(focus) 3. number of focal points(Multi-focus) 4. image shape and size(Scan range and wide view) 5. line density(Frame Rate) |
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what equation effects focusing?
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LATA: Beam width
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focal Number: Mult focusing: what is is effecting?
equations? |
Optimizing LATA w
super low FR: 2/dl |
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Image Shape: what is effected wtih sector or vector
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frame rate: v/2dl
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frame Rate: what does it control? and what is the outcome? 2 things
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Line density is LOW and therefore higher FR: LATA sucks but FR is good
Line density is HIGH and therefore lower FR: LATA is good, but FR sucks |
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POWER: how works
can sonographer control it? |
master syncronyzer produces voltage and then to probe:
VOLTAGE ~ POWER ~ INTENSITY of wave therefore, output is regulated by voltage from pulser and SONOGRAPHER CAN CONTROL IT |
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POWER : OTHER NAMES
6 |
acoustic power
transducer output output gain pulser power energy output transmitter power |
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DOWNFALL OF POWER?
Benefits of POWER? Another name for power? |
bioeffects
image will be brighter Mechanical INDEX |
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CALCULATION: your machine output power is set at _6dB. what percenttage of Max power is being used
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25%
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function of Transducer
1. 2. 3. 4. |
1. turns electric into acoustic power(converse piezoelectric Effect)
2. Sends US signal 3. Receives Echos 4. Turns acoustic into electric pulse(piezoelectric Effect) |
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what to select about transducers
2 things |
Shape and size
frequency: high: shallow Low: deep |
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Receiver: defined
5 steps of processing |
gets electrical signal from the transducer, processes it and prepare it for display
Compensation Compression Amplification Rejection Demodulation |
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Function of Receiver: A________
Another name(s): defined |
Amplification
Gain Adjusts the amplitude of the received signal |
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Function of Receiver: C________: the varied one
Another name(s): defined What equation: |
Compensation
TGS adjust received amplitude separately. Amplitude from deep is smaller than shallow and needs adjusting (mu)df |
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Function of Receiver: C________
Another name(s): defined |
Compression: squishes into Dynamic Range
Dynamic Range DR includes all values from max to min. Amplitude sent is 10 to the 10/15 times bigger than received: compressed to reduce this diff |
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Function of Receiver: R________
Another name(s): defined |
Rejection:
Precision low amplitudes have no clinical significance and are rejected: extra noise |
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Function of Receiver: D________
Another name(s): defined |
Demodulation:
RECTIFICATION: turns negative voltage to postive SMOOTHING: places envelope around the bumps Changes the shape of the electrical signal to be accepted by display: Sonographer does not control |
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Scan Converter: defined
what doing? |
Stores and electronically process info from the receiver:
1 received in ANALOG 2 stored and processed in DIGITAL 3 displayed in ANALOG |
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What is analog
what is digital |
ANALOG:format has an infinite number of values
DIGITAL:format has set number of values |
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AD Converter
DA Converter |
converts analog to digital
converts digital to analog |
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How is data acquired and displayed
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vertical
horizontal |
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Pixels: defined
where and what screen : 3 things |
digital picture divided: smallest image unit
More pixels: better image x coordinates: on a line y coordinates: depth Color represents AMPLITUDE: Z mismatched |
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memory piece: Defined
where do these go? |
bit: memory stores
in pixels 2n 2 to the n(bit) power to get more shades 2(1) = 1 (0,1) 2(2) = 4 (00,01,10,11): 2(3) = 8 (000,010,010,011, etc) |
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EXAMPLE 4
How many shades of gray can be displayed if the system has 5 bits per pixes ratio? |
2 (5) = 32 shades
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EXAMPLE 5
even though human eye can distinguish about 20 shades of gray, modern diagnostic US systems normally offer 256 diff brightness levels. what is the bit per pixes for that ratio? |
2 (x) = 256
=8 |
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Contrast resolution:
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More pixels with make it better.
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Preprocessing
Postprocessing |
transducer (analog)
receiver (analog) AD converter MEMORY DA converter Display |
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Write Zoom: defined
when: |
image is rescanned but smaller: does not affect FR
Pre-processing: live action |
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Read Zoom: defined
when: |
already stored image is magnified:
post processing: after freeze |
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Post-processing: P____________
:frames defined what is it doing: looking like? |
Persistence: averages frames to minimize NOISE
Not good for speedy imaging: not effect FR, but adds them together. Post process |
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E_____ E___________:
pre or post processing: defined what is it doing? |
Edge Enhancement: post-processing
averages several PIXELS for smooth vs. sharp appearance. DECREASE to get smooth image: MORE average: better contrast INCREASE to get sharper, grainy: LESS average: better detail resolution |
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Compounding
S______ C_________: pre post? defined F______ C_________:pre post defined |
Spacial Compounding: both & post. DECREASES FR
Rescans several times with steering and then add them. Frequency Compounding: Post High f: better LARD and Low f: better penetration COMBINES data in single image to improve penetration and resolution WITH BOTH: Better FR than just spacial but still lower |
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Post-processing
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choose different gray scales for what we like.
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Contrast resolution: other name
depends on 5 things |
GRAY SCALE:
acoustic impedance scan converter: #bits/pixels post-process curves monitor setting: contrast/brightness ambient light in room |
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Harmonics: defined
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2x
3x 4x fundamental frequency |
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EXAMPLE 6
what frequencies are harmonic to the 2.5 MHz? |
2x 2.5=5
3x 2.5=7.5 4x2.5=10 etc |
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Non sinusoidal wave is :
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sum of central FUNDAMENTAL frequency and its harmonics
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Harmonic Imaging: How created
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waves of rarefraction/compression
Compression denser/stiffer stiffness inverse to velocity therefore DISTORTION of sinusoidal wave makes it NO LONGER SINUSOIDAL and therefore has harmonics |
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Harmonice Imaging: how and why good (5 things)?
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Filter out Fundamental frequencies
:) LARD improves: 1/2 nv/f :) LATA improves: high f in center of beam :) Other artifacts decline: reverb, side lobes :( Attenuation increase :( FR may lower: requires two pulses to go out |
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LARD in Harmonics: what is happening
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the broadband widths overlap. longer pulse is sent out to avoid this and therefore LARD will be little worse as the 1/2 SPL or 1/2 nv/f will go down. f will be higher.
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Pulse (Phase) Inversion: defined
what is it improving? what is happening advantages: 2 |
sending out two harmonic impulses to generate CONSTRUCTIVE interference.
Improves LARD: does not need long pulse Advantages: no need for narrow bandwidth signal with fundamental frequency is eliminated |
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Types of Harmonic Imaging
3 kinds |
Tissue Harmonic Imaging: THI: NO contrast
Harmonic Imaging w/ contrast: bubble study Color/Power Doppler Harmonic Imaging: w/ contrast |
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Coded Excitation
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NOT available for us
sends out several pulse patterns and don't have to wait for one to return. maintains High Res spacial resolution |
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Extra 2D imaging extras: 3 of them
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up down invert
right left invert colorize maps: whole thing |
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Video display
3 kinds |
CRT: cathode ray tube: ANALOG:cathode ray tube emits electrons that are scanned across the phosphorescently coated screen
LCD: Liquid Crystal display: FLAT: replacing CRT DLP: digital light processing chips: FLAT: uses millions of tiny mirrors |
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Video Formats:
2 of them |
DICOM: purest uncompressed format used by all US systems
lots of memory (uncompressed) and NOT compatible with computers CODEC: allows compression of data for storage: AVI, MOV, WMF, MPG4 etc |
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Storage Media:
3 of them |
Hard copy: charts
Magnetic: tapes Optical :discs |
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RAID: storage
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redundant array of independent disks
storage technology that combines multiple disk drives components into a logical unit. distributed in RAID levels |
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Doppler: away and toward
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For both the source and receiver
Away: lower frequency: Toward: higher frequency |
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Motion of the Receiver
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(v+-v(receiver)
f'= ___________ fo (v-+v(source) top (toward) bottom(away) |
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SAMPLE: you are at the train stateion when the train whistlse at 900 Hz going by. train moves with the speed of 60 km/h. what frequency will you hear when the train approaches you? what frequency will you hear when the train leaves the station? speed of sound is 340 m/s
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946 Hz
857.9 Hz |
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you are on the train passing kfalls. I am at the station waiving and blowing a horn at 100Hz. train moves with the speed of 60km/h. what f will you hear when the train approaches kf station? what f will you hear when the train leave kf station? speed of sound is 340 m/s
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104.8 Hz
95.1 Hz |
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train approaches the station from the west at 60km/h and emitting sound of 400Hz. at the same time a car goes east at 30km/h. what f does the car driver hear? speed of sound is 340 m/s
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410.0 m/s
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Doppler shift: definition.
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change of frequency of sound due to relative motion of sound source and receiver.
^f = f(received) - f(source) ^f=f'-fo |
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Doppler Shift with blood
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2 fo v(blood) CosO
^f = ------------------------------- v |
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Doppler shift
positive negative |
f' > fo
f' < fo |
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What is angle for zero doppler shift?
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<0 = 90 degrees
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what is maximum angle for doppler shift:
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0 degrees
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what is optimal doppler shift for consistency assume?
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< 60 degrees
45 - 60 degrees |
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Doppler HISTORY
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1842: musician and train
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Who used doppler to detect blood flow in arteries and when
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sotomura in 1957
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who built a spectrum analyzer to look at doppler display? and when
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Kaneco 1960 ish
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who first used Doppler intended for transcutaneous measurement of blood flow in MAN. Used CW doppler
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Baker and Stegall: 1964
pulsed dopper was introduced |
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when and who combined B-mode US and doppler. DUPLEXING
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Barber 1974
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When did TRIPLEXING come about
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late 1970s
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what is the formula for v(blood) Cc
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1540 m/x ^f
v(blood) = ---------------------- 2 fo Cos0 |
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what is the velocity of the blood in the vessel scanned by 2.5 MHz probe if the system determines 1KHz doppler shift? doppler angle is 60 degrees.
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0.6 m/s towards
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what is the velocity of the blood in the vessel scanned by 11 MHz probe, if the system determines 3KHz Doppler shitf? angle is 60 degrees
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0.4 m/s towards
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what are limitations of audio doppler?
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subjective interpretation
lack of permanent objective record |
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stethascope v. doppler audio
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Stethascope: vibrations or pressure waves as a result of rapid accelerations and decelerations of blood
doppler audio: audible display of the Doppler f shift produced by the shift of blood. NOT Occur in nature. |
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spectral analysis?
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Graph of v or ^f v. time
flow toward: above baseline |
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what does brightness on the spectral analysis represent?
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amplitude: related to the amount of blood moving at a certain velocity.
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flow is laminar:
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accelerating and decelerating at approximately the same velocities: an envelope of the similiar velocities
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Turbulant flow:
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diff velocities detected at any one time. wide spectrum of velocities. display of velocities that are low, mid and high: spectral broadening or window filling
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PW doppler: Guidelines
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1. long axis
2. cursor parallel to the flow or to wall 3. angle at 45-60 degree : when higher, overestimate when under 30, critical angle. 0 maximum. 4. sample gate size: 2/3 of vessel: in veins: wider |
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Aliasing: definition. How computer its getting it and displays it
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signals is recieved in analog format
AD converter converts the signal into digital |
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Nyquist limit:
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states that for accurate reconstruction of the waveform, each cycle must be sampled at least 2 times
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1. in the AD converter: what is the rate of sampling
2. in the DA converter: what does it do? 3. what if velocity too high? what happens if there is not enough sampling to recreate the high doppler shift |
1. PRF
2. reconstructs the waveform: Nyquist limit of 2 samples needs to be met. 3. the recreated doppler shift will be lower than the real doppler f and therefore will aliase. v(blood) will be calculated low. The higher the PRF the better |
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Aliasing is
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an artifact due to an insufficient sampling
^f is more than the PRF |
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waht happens to the scale if the f of the transducer is increased by a factor of 2
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(1540)2
--------------- 8 fo d CosO scale decreases by 2 |
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how is scale affected, if the depth of a sampled vessel doubles?
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(1540)2
--------------- 8 fo d CosO answer, decreases by 2 |
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what happens to the scale if the angle of insonation doubles
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(1540)2
--------------- 8 fo d CosO if angles increases, the Cos0 goes down and therefore increasing the scale |
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what is the formula for blood velocity if there is no aliasing?
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(1540)2
v(blood) < = -------------- 8 fo d cosO |
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will aliasing occur, if the PRF is 8Khz and the doppler shift if 5kHz
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False statement:
^f <= 1/2 PRF nv/f 5Hz |
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will aliasing occur, if the depth of imaging is 12cm and the doppler shift is 100Hz?
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True statement:
^f <= 1/2 PRF nv/f 100 hz<= 3208.3Hz |
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will aliasing occur fi the depth of imaging is 10 cm and blood flow v is 100 cm/s. angle is 60 degrees. Assume a 5 Mhz probe in use
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True
100 cm/s <=120cm/s |
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Things to do to avoid aliasing:
6 things |
increase PRF(scale)
Increase doppler angle decrease f of transducer decrease depth decrease baseline (1540)2 --------------- 8 fo d CosO use CW |
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What are the 2 catch 22s for fixing aliasing from a deep vessel?
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Using a high frequency transducer gives:
good scale resolution low scale and low penetration |
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Doppler Modes: 2 of them?
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CW
PW |
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CW probe uses how many crystals at a minimum?
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2
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What is the are of focus called for CW?
2 names |
focal volume or sensativity
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Does CW have a PRF max and why not or why so
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no. it is on all the time
No way to determine depth |
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CW positive features
3 of them. CW negative features 3 of them |
NO aliasing
cheep and simple Good sensativity Unknown depth no imaging detects any/all motions in line(wall, etc.) |
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PW uses a minimum of _____ crystals
what is the process? |
1
send pulse and listen for return |
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where is the doppler shift received from?
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sample volume
gate |
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the frequency of a pulsed wave depends on what? and what is the formula?
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thickness of the crystal
vcr f pw = ------- 2th |
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GATE info:
there are two sets of "times" to receive the data back to the transducer |
sending and listening
It takes 13 usec to go 1 cm. |
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Range ambiguity: what are you turning up to get it to work?
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f<=PRF<= v/2d
Example: if the PRF 7.7 Khz and the depth is 12cm. 1540m/s ------------- = 6.4 Khz and this is now FALSE 2 x .12 m |
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Comparison of PW and CW
Range ambiguity? smaller and larger? Aliasing? does it occur? Imaging? possible or not? |
CW is larger and PW is small(only in gate)
CW never and PW sometimes if scale is too small CW never and PW possible |
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Comparison of Imaging(2D) and PW doppler
Pulse duration? Optimal angle? Frequency? Sensativity? |
Short(better LARD) and long
90 degrees and 0 degrees High f for better LARD and low F for aliasing NOT sensative to low: Sensative to low |
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What does Pulser control?
8 of them |
Gate location
Gate size Steer angle PRF/scale Depth Doppler Frequency Acoustic power PW/CW/HPRF |
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Gate Size:
one main rule |
2/3 of the vessel but wider for veins
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Steering. what control?
and what are the rules 3 things to help |
Heal toe
change cursor change line of insonation |
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Scale: on the graph, scale is on the x/y axis?
what is it affected by? |
y axis
PRF (1540)2 PRF x 1540 depth of gate -------------- ---------------- Doppler f 8 fo d CosQ 4 fo CosQ Doppler Angle |
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Doppler fo
Where does it come from? High or low for aliasing? |
The receiver and the mixer: LOW PASS FILTER
need to keep lower than the scale to not alias |
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Acoustic Power is ????
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Amplitude
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Doppler Receiver components,
5 and what do they do |
Amplitude: gives enough Amplitude to register
MIxer: in and out of phase: real and imaginary Low Pass Filter: ^f detection Quadrature detection: Direction of flow detection Wall Filter: high pass filter: |
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Another name for Doppler Shift detection,
LOW PASS FILTER? 2 of them What is it finding? |
demodulation
heterodyning only finds a numberical value (positive or negative) uses rectifying and smoothing: all an absolute value for a number. |
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What is Zero Crossing Detection
Another name? |
finding the doppler frequency with each crossing of the zero line
Time interval histogram |
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Quadrature detection
what is it finding? |
only finding direction.
uses the low pass filter of both the real and imaginary. If positive number, it is toward and real is leading if negative number, it is away and real is lagging |
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two old flow direction techniques
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heterodyne detector
single-sideband detector |
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Wall Filter: what kind of filter
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high pass filter: deletes the noise and low f items
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FFT: what is the name and what does it do
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Fast Fourier Transformer
Doppler frequency separates to diff frequencies reordered in a FREQUENCY DOMAIN Blood velocities are then converted to TIME DOMAIN. x=velocity, y=time, z=amplitude:volume |
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Doppler Compression
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Dynamic Range: Decrease the range from the brightest to the dullest:
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Gamma: POST PROCESS
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change all the gray scales
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Sweep speed:
if Brady: do what if Tachy: do what |
adjusts the scale along the x axis
Brady: decrease Tachy: increase |
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Doppler Map: what is it
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colors only
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Invert:
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flow towards or away
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Baseline
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Adjusts the fraction displayed toward or away
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Pixel Ratio:
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affects the hight and width of a pixel
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Dopplerk 5 things you do to adjust your first imaging
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LONG axis of the vessel
fix angle: 45-60 and 2/3 gate scale filter gain |
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Color mode: information is presented how on the screen:
pixel dimensions |
length,
width velocity(color) |
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Color gate is small/large
What button/feature regulates LINE DENSITY |
large
FRAME RATE button |
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Color maps: top and bottom?
middle of maps BART and RABT |
towards and away
lower velocities Blue away and Red away |
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where is Caudle and Cephalic
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Cephalic Left and CAudle Right
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Doppler Packet: what is it?
2 other names what does several pulses represent? does this increase or decrease the FR |
^f from several pulses and averages them.
Packet Size or Data Number higher velocity measurement decreases it. affecting temporal resolution |
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Color Map Varience Mode
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changes from side to side as well as toward and away.
turbulance is on the right |
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Power doppler
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no direction or velocity evaluated: sensative to low flow
Also called *ultrasound angiography *amplitude doppler *color amplitude imaging (CAI) |
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Color Doppler Velocity Detection:
2 of them |
Cross-Correlation
Doppler |
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What does color detection: cross correlation use to process the data. and how does it find that>?
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Uses Range Equation
MODAL |
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What does color detection: doppler use to process the data. and how does it find that>?
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Auto correlation
MEAN |
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Comparision color & Spectral
Area evealuated? Accuracey Technique 3D info: x y z |
Large small(gate)
less, mean/modal high Spectrum Doppler/Cross C Doppler L W v t v A |
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5 things to adjust first for Color
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Steer Box
C Gain C Filter C Scale good Vessel image |
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What does Color Pulser Do?
7 |
Power,
Freq Box size Box location PRF Steer Data number |
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Color : Acoustic Power
what does? when increase? when decrease? |
increase for filling:
Patient exposure too |
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C Frequency:
what does? when increase? when decrease? |
Increase: better Axial Resolution
Decrease: Better depth Decrease to go under scale for aliasing |
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color box
what does? How affect FR? |
wider and deeper: FR down
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Steering:
what does? |
gets best angle. tree fall, box fall
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Frame Rate:
what does? when increase? when decrease? |
increase to increase FR but worse filling: better to see velocity: LATA :)
decrease to decrease FR but better filling: better filling: LATA :( FR=PRF/l or v/2dl |
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Data Number:
what does? when increase? when decrease? |
Increase: Lower FR: See velocity better
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Scale: same or different than doppler?
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same
PRF change |
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Color Gain:
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Amplification
clean up or add noise: |
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color Filter:
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High Pass: removes low frequencies
increase to get rid of noise detect to see slow stuff |
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Scan Converter: Dessert Items
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Reverse :invert map
Map type: color Smooth: Persistance: Frames Baseline |
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Receiver: color
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Gain and Filter
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Color Frame Interpolate:
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Adds frames: post process: Smoothing: fill in the blanks
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q
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Color Persistence:
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Average Frames
no FR affect Temporal resolution down |
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Color Time Smooth:
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Average Lines
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Color Priority:
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turn off if you want. Stupid
Prioritize color over black and white |
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