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54 Cards in this Set
- Front
- Back
The 3 main colors used in doppler are?
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green red and blue
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Define packet
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The number of pulses per line
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Define packet size
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The accuracy of doppler velocity measuremtnes depends upon the pulses in the packet. THe more pulses in the packet the more accurate is the velocity measurement. As the packet size increases, more time is required to acquire doppler information.
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Smaller packets lead to...
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Inaccurate flow measurements.
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Larger packets lead to ....
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Low frame rates
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The following will result when the packet has more pulses...
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* The velocity measurement is more accurate
* More time is required to collect data from each scan line *More pulses are needed to make a single frame * The frame rate is lower * The temporal resolution is reduced |
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In what way is aliasing potential in pulsed wave and why?
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Intermittent sample
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What are the advatages and disadvantages of continuous wave doppler?
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Advantages: Able to measure very high velocities
Disadvantages: Echoes arise from entire length of overlap between the transmit and recieve beams. This is range ambiguity. |
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How do you adjust the color when the frame rate is down, temporal resolution is down???
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Increase the frame rate and temporal resolution by:
*Minimize depth view *Use single focus (not multi focus) *Narrow sector *minimize the line density hint: Decrease the color box and make the width of the box smaller |
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How do you adjust the aliasing artifact??
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Increase the scale, shallow depth, lower frequency, angle closer to 90 degrees.
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Define Inspiration
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1. Pressure within the abdominal cavity increases
2. venous flow in leg decreases 3. pressure within the thorax decreases 4. venous return to the heart increases * flow from 1 arms 2 Abdomen into the thorax is called venous return to the heart |
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Describe the venous pressure in the lower extremities...
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It decreases with inspiration and increases with expiration.
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Describe blood flow
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Blood flow when the total fluid energy at one location differs from the total fluid energy at another location this is called energy gradient or pressure gradient.
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Hydrostatic pressure gravity
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A column of blood has weight Hydrostatic pressure equals the weight of the blood pressing agaiinst the vessels from the heart level to point of measurement.
Below heart- Pressure measured below the heart level equals circulatory pressure plus the weight of the column of blood. Above the heart- Pressure measured above the heart level equals circulatory pressure minus the weight of the column of blood. |
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At what degree could a bioeffect occur?
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Anything over 2 degrees centigrade or celsies could cause thermally induced biological effects
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WHat is the result for a biological effect?
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None
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WHen will there be a biological effect on the fetus?
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At 41 degrees
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How is the SPTA value related to the bioeffect?
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*AIUM's and FDA's bioeffects intensity limit SPTA
100 mw/cm2 unfocused 1w/cm2 or 1000 mw/cm2 focused *** Difficult to study in vivo ( in living tissures ) because of attenuation ( scattering, absorption and reflection) |
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WHat is the difference of intensity in focusing and unfocusing?
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100mw/cm2 unfocused
1w/cm2 or 1000mw/cm2 focused Unfocused is more intense |
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What instruments are used for measuring output power?
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Hydrophone, radiation force, Acoustic-optics, calorimeter, thermocouple
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Mechanical index is related to???
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High pressure, low frequency
You will get low cavitation, harmonic. |
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What is the effect of the acoustic exposure?
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Transmit power, increased PRF, increased scale
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A
What does ALARA stand for? |
As low as resonalbly achieved
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What is the bioeffect on a pregnant mouse?
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Found Neurocranial damage with the continuous wave doppler.
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What is the meaning of
VIVO? |
Living
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What is the meaning of
VITRO?? |
Non living
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Define spectral analysis
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It is performed to extract or identify the individual frequencies making up the complex signal. It is used to interpret individual velocites in the signal.
Early methods: Zero crossing detection, time interval histograms. chirpz-transforms Current methods: Fast fourier transform (FFT) used for pulsed or continuous wave Doppler. Autocorrelation or correlation function- used for color flow doppler * Both are digital techniques that are performed by computers. Autocorrelation is used with color doppler because of the enormous amount of doppler information that requires processing. Autocorrelation is slightly less accurat, but substantially faster than FFT. |
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Define viscoelasticity
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Energy distortion in the medium and irreversibly converted to heat.
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Define relaxation?
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Diaphragm in the neutral position.
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Define inspiration?
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Inspiration:
* the diaphragm descends into the abdominal cavity. * Pressure within the abdominal cavity increases * Pressure within the thorax decreases * Venous return to the heart increases |
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Define Expiration
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THe diaphragm ascends into the thorax.
* Pressure within the abdominal cavity decreases *Venous flow in legs increases *Pressure within the thorax increases *Venous return to the heart decreases. HINT: flow in the lower extremities moves with the diaphragm. The opposite flow changes occur with venous return to the heart |
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BREATH IN!
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***Diaphragm descends
***venous flow in legs decreases ***venous returns to the heart decreases. |
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BREATH OUT!!!
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***Diaphragm ascends
***venous flow in legs increases ***Venous return to the heart decreases. |
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What is the process of acoustic energy absorption?
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Attenuation
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What is the meaning of artifact?
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1. Not real
2. Missing reflectors, 3. Improper size, shape, position and brightness |
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What is AIUM 100
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AIUM 100 mm test object: commercially available, array of strategically located pins.
Speed prop speed of soft tissue 1,540 m/s Attenuation- does not have attenuation properties of soft tissue. |
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What is Phantom?
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Tissue equivalent phantom- commercially available contains a medium similar to soft tissue. Strategically located pins. structures that mimic cysts and solid masses are embedded in the phandom.
SPEED- In phantom, sound has a velocity of 1,540 m/s |
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ATTENUATION COEFFICIENT SIMILAR TO SOFT TISSUE
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Useful in evaluating gray scale since it attenuates like soft tissue. Commercially available contains static simulated vessels as well as dynamic simulated vessels at a variety of angles
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Spatial pulse length, lateral resolution is related to the ??
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Focus beam
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Flow towards the transducer
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Increase frequency
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Flow moving away from the transducer
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A decrease in frequency
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Frequency shift is always related to???
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Velocity
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List the intensities from greatest to least...
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SPTP>>IM (intensity maximum) >> SPPA>> SPTA >> SATA
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Axial resolution
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Synonym: LARRD
The ability to distinguish two structures that are close to eachother front to back, parallel to or along the beam's main axis. |
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Output power
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Affects brightness by adjusting the strength of the sound pulse sent to the body by the transducer. When the pulse is more powerful all of the returning echoes from the body are stronger, and the image is brighter. When the image is too bright due high output power the lateral and longitudinal resolution degrade.
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Reciever Gain
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Affects the brightness by changing the amplification of the electronic signals after returning to the reciever. When amplification is increased, the electronic signals in the reciever are boosted and the image will be brighter.
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When does the control affect output power or reciever gain?
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When the control term suggests output most likely the function is output power. WHen the control term suggests reception or incoming the most likely function is reciever gain.
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What is the meaning of Doppler shift (doppler frequency)???
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The change or variation in the frequency of sound as a result of motion between the sound source and reciever.
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Greater velocities create greater.....
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Doppler shifts
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The difference between transmitted and recieved frequencies is refered to as what?
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Doppler shift or doppler
Frequency |
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What is a positive shift?
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When the source is moving toward the transducer.
Reflected frequency is higher than transmitted. |
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what is a negative shift?
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When the source moves away from the transducer. Reflected frequency is less than the transmitted frequency.
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Doppler measures frequency shift not.....
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AMPLITUDE
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The typical value for Doppler is??
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20-20,000 hz or 20 khz
This is audible sound |