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113 Cards in this Set
- Front
- Back
During Doppler exams the u/s system measures the difference between the transmitted and recieved frequencies called
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Doppler Shift
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Which factor MOST determines axial resolution
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Spatial pulse length
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The attenuation Coefficient is expressed by which of the following
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dB/cm/MHz
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The alara principel related to
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Using min. power and exposure time to u/s
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The detected signal amplitude from smallest to largest is equivalent to the system's
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Dynamic Range
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Which of the following factors MOST affects lateral resolution
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beam/transducer diameter
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The density of a medium and the propagation speed of sound are
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Inversly proportional
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The term that describes the size of the transducer surface involved in processing the ultrasound beamand detection of echoes for each beam line is
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Aperature
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In order for a refracted wave to be produced which of the following conditions must occur at an interface
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Oblique Incidence,
different sound speeds |
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Which of the following factors determins a transducer resonance frequency
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crystal thickness
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If a study produced no false positive results it would have 100%
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specificity
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Most color flow systems prosess the color utilizing
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autocorrelation
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According to the AUIM no confirmed bioeffects have been reported on patients or operators, below what intensity for imaging
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100mW/cm2
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Impedence is best defined as
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The product of the density and the propagation speed
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Which term describes the crystals capacity to be excited by an electric impulse to generate a mechanical sound wave as it expands;and conversly transform a detected mechanical soundwave into a electric impulse
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Peisoelectric effect
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What ratio represents the Higheat Intensity
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STPT
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A slice thickness artifact is Most likely the result of which of the following
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Beam diameter larger than the reflector
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Which term BEST describes the rate of energy transfer that occurs during a specific period of time
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Power
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The redirection of sound in many direction by a rough surface or by a heterogeneous media is called
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Scattering
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As lateral resolution improves, the beam diameter will be
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Reduced
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The axial resolution of the image improves as you
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increase the frequency of the transducer
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Which of the following will NOT improve frame rate
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Using a larger aperature probe
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For an U/S system to display 256 shade of gray it would require ____ deep image memory
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8 bit
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Based upon the doppler equation, the doppler shift is linearly proportional to which of the following
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Tranmit doppler frequency
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Rank these four media in the increasing order of propagation speed.
bone,fat,air,soft tissue |
Air, fat, soft tissue, bone
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What is reflection
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result of a soundwave being redirected back toward the transducer
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Sound wave are
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longitudinal,mechanical
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The speed in soft tissue is
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1540m/s
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what are the acoustic variables
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density, pressure, temperature
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The effect of soft tissue on US are
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acoustic propagation properties
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Time for one cycle to occur
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period
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Distance covered by one cycle
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wavelength
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If the frequency of US is increased from 0.77mhz to 1.54mhz, what happens to the propagation speed
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remains the same
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The units of pulse repetition frequency are
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per minute
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Time from the begining of a pulse to its end is
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pulse duration
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Range resolution is determined by what
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Spatial pulse length
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If a wave's apmlitude is doubled what happens to the power
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quadrupled
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Power of sound has units of what
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watts
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If the Intensity of a sound beam remains unchanged while the beam area is reduced in half, what happens to the power
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halved
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Put these intensities in decreasing order
SATP SPTP SATA |
SPTP SATP SATA
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The duty factor for continuous wave US is
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1.0
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The units of attenuation are?
What kind of scale? |
dB
logarithmic |
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The rayl is the unit of
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impedance
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What are attenuations 3 compnents
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scattering, reflection, absorption
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For soft tissue, the approximate attenuation coef. in dB/cm is equal to one-half
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Frequency in Mhz
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AS the impedance of 2 media become vaslty different the
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reflection increses
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The angle between an US pulse and the boundry between media is 90degrees
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orthononal incidence
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The ALARA principle relates to
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using min output and exposure
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Frequewncy, prp,amplitude,duty factor can be calculated with an PTZ element attached to an oscilloscope instrument called
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Hydrophone
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The 2 mechanisms of bioeffects are thermal and cavitation. T ot F
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True
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Small microbubbles that occur as a result of violent molecular agitations are called
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cavitation
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The AUIM has issued a statement saying no confirmed biological effects on patients or instrument operators have been reported at intensities below
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100mW/cm2
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THe beam profile is measure by what method
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acoustic optics
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Crystals are utilized to evaluate the total power of the beam by converting energy into heat is called
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calorimeter
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High reciever gain will increase the intensity of the sound
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False high output power
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THe method of identifying and measuring the parts of the US that have the potential for producing bioeffects is called
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Dosimetry
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An artifact that appears as multiple reflections equally spaced is called
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reverberation
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Grating Lobe artifacts occur with______transducers.
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array
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Refraction causes lateral displacement of the reflector and is caused by______ incidence.
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Oblique
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Propagations speed errors occur because the equipment assumes a speed of soud in tissue of 1.54 mm/microsec.
T or F |
True
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Multipath artifacts are caused by the sound beam interacting with a_____ surface.
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smooth
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2 types of useful artifacts
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enhancement, shadowing
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Section thickness artiffacts result from a propagation speed error.
T or F |
False- beam width
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Color mirror image artifacts can be elimanated by reducing the sector size.
T or F |
False- color doppler gain
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Aliasing occurs when the reflected frequency exceeds ___ the nyquist limit.
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1/2
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Enhancement occurs when the sound beam travels through a medium with an attenuation rate_____ than the surrounding tissue
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lower
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2 catagories of energy that make up total fluid energy are
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potential and kinetic energy
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Potential energy is stored energy. T or F
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True
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Rule that states that fluid is neither created nor destroyed as it flows through a tube is
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Continuity
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As resistance of blood flow through the aartery increases, the pressure drop across the artery will
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increase
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As the vessel lumen size decreases, blood flow velocity will
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Increase
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When the vessel lumen size increses, blood flow velocity will
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decrease
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If the radius of the blood vessel is decreased by one half, the velocity of the blood flow will
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increase four fold
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The inverse relationship between pressure and velocity is described by
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Bernoulli's equation
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A high Reynolds number indicated ____ flow
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turbulent
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The primary contributing factor to venous blood flow in the upper and lower extremity include
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heart contraction\
intraluminal blood pressure peripheal resistance in the capillary bed |
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When colateral blood flow develops, resistance at that level will
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decrease
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When a patient with a stenotic lesion is exercised, the pressure gradient at the site of the stenosis will
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increase
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Transmural pressure is the difference or gradient between the intramural and tissue pressure
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True
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When tissue pressure exceeds intramural pressure, the viens will
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compress
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If the right atrial pressure or central venous pressure is increased, the veins in the body usually are
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dialted
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Hydrostatic presssure does not have the same value for the arteries as it does for the veins
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False
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As venous blood is moved out of the calf veins, intrmural and transmural pressure drops
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True
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Factors affecting the blood flow within the body include
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Density of blood
velocity of blood size of vessel |
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Difference between the transmit frequency and the recieved frequency is called
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Doppler shift
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What angle provides the max doppler shift
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0 degrees
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Continuous wave doppler utilized ______elements
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2
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Flow towards the transducer is displayed _____ the 0 baseline
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above
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The units for the doppler shift are
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Khz
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The nyquist lismit is equal to _____ of PRF
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1/2
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Mirror image artifact occur because of
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too much doppler gain
poor doopler angle |
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PRF is related to depth of pulse travel
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True
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Aliasing is a diagnostic parameter for severe disease
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False
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Window filling of the spectral tracing is caused by
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turbulent flow
sample gate too large sample volume placed too close to vessel wall doppler gain too high |
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The type of flow pattern seen in medium and large size vessels is reffered to as
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plug flow
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Color flow doppler provides ______ velocity information
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average
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The color assigned to flow towards the transducer is
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Red
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The type of processing utilized with most color flow systems is
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autocorrelation
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A mininmum of 3 pulses per line is required to assign a color
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True
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Color aliasing is seen when red and blue are seperated by black. T or F
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False
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No flow within a vessel would be indicated by a_____ color.
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Black
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Color frame rate is affected by all of the following
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sector size
color box size PRF |
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The purpose of the wall filter is to
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eliminate high amplitude noise artifacts
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On color flow imaging, the best way to overcome aliasing is
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use high Prf number
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The color priority on color flow instruments is used to
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decide the relative contribution of color/echoes in the image
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The color map represents the
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mean doppler shifts only
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the angle corrector is used for
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align the u/s beam with the vessel lumen
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Aliasing is found in all of the following imaging modes
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color doppler
spectral pulsed doppler |
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Which of the following factors is not dtermined in the doppler equation
a.doppler angle b.incident frequency c.reflector speed d.acoustic information |
acoustic information
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PWD instruments are characterized because of their ability to do all of the following except:
a.real time spectral doppler b.gate position c.velocity estimation d.velocity limits unrestriction |
Velocity limits unrestriction
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The method used by CW doppler to discriminate valuable signals is the
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zero-crossing detector
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In laminar flow, blood is seen to move
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in layers
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In doppler systems, changing the PRF is equal to changing the
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velocity scale
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