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45 Cards in this Set
- Front
- Back
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remember this hint when dealing with breathing and venous flow:
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"legs go with diaphragm, return to heart is opposite"
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laminar flow may have _____ or _____ patterns.
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parabolic, plug
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2 charecteristics of laminar flow:
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-similar velocities
-narrow doppler spectra |
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2 charecteristics of turbulent flow:
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different velocities
wider doppler spectra |
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a unitless number indicating laminar or turbulent flow:
what is laminar? Turbulent? |
Reynold's Number
L- <1500 T- >2000 |
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blood flows when:
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the total fluid energy at one location differs from the total fluid energy at another location.
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what are the three forms of energy loss in blood?
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frictional
viscous inertial |
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what are the units of viscosity?
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poise
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describes the thickness of a fluid
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viscosity
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when a pt. is in the supine possition, what is the hydrostatic pressure?
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= 0. EVERYWHERE IN THE BODY
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difference between received and transmitted frequencies:
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doppler shift
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when reflected frequency is higher than transmitted this indicates:
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possitive change (or shift)
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when reflected frequency is less than transmitted this indicates:
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negative change
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t/f
doppler measures amplitutde? |
false
measures freq. shift |
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what are the typical values of doppler shift?
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20Hz-20kHz
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flow towards transducer?
flow away from transducer? |
increased freq.
decreased freq. |
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doppler shift=??
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received freq - transmitted freq.
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doppler shift = ???
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2 x reflector speed x incident freq x cos(angle) / prop. speed
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doppler shift is directly related to:
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-red blood cell speed
-freq. of transducer -cos of angle between flow and sound beam |
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doppler shift is inversly related to:
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speed of sound in the medium
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t/f
doppler measures speed? |
false
velocity |
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what is the cosine for the following angles?
-0 deg. -60 deg. -90 deg. |
-1
-0.5 -0 |
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used with uni-directional doppler
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non-coherent processing
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used in bi-directional doppler
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phase quadrature
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# of crystals in CW doppler?
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two
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advantage of CW doppler?
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able to measure very high velocities accurately
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# of crystals in PW doppler?
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one
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t/f
we select the location of the sample gate? |
true
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simultaneous imaging and doppler is known as:
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duplex us
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the doppler freq. at which aliasing occurs
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nyquist freq.
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nyquist limit =??
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prf/2
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_______ sample volumes create doppler spectra with LARGER, cleaner envelopes.
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smaller
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_______ sample volumes create doppler spectra with smaller envelopes (spectral broadening)
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larger
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the x-axis of a doppler spectrum is
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time
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the y-axis of a doppler spectrum is
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doppler shift or velocity
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gray shades on a doppler spectrum are related to:
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-amplitude of the reflected signal
-# of rbc's creating the reflection |
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color doppler is pulsed US technique and is subject to:
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range resolution or specifity
aliasing |
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color doppler reports:
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average (mean) velocities
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laminar flow-
turbulent flow- |
lt sided colors
rt sided colors |
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color jet size is most affected by:
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color doppler gain
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several pulses used to determine red blood cell velocities by doppler
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packet or ensemble length
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the packet size must balance between
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accurate velocity measurements
temporal resolution |
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spectral doppler (pulsed and CW) measures:
Color flow measures: |
peak velocity
mean velocity |
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what is the diff between speed and velocity?
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speed has only a magnitutde, while velocity has both magnitude and direction
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what is the current method of producing dopple signals?
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pulsed and CW- FTT
autocorrelation for color flow doppler |
