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218 Cards in this Set
- Front
- Back
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What are the general frequencies used in ultrasound imaging and name a type of exam used for the transducers.
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2.0-Cardiac, 3.5-OB/Abdominal, 5.0-Vascular, 7.5-Superficial, 10.0-Small parts
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Define bandwith.
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The range of frequencies contained within a pulse
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What is better Narrow or broad bandwidth?
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Broad due to the larger spectrum of frequencies
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What is the main pulse that is emitted from the transducer termed?
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Operating/Resonance
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What is the process that increases the range of frequencies called?
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Damping
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Define Velocity.
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Speed with direction of motion specified
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What is velocity determined by?
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Density and stiffness
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What is the formula for propagation speed?
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C=wavelength*Freq
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What 2 variables determine the mediums properties?
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Stiffness-resistance of a material to compression, and Density-concentration of mass per unit of volume
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What is the rule of thumb regarding propagation speed?
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Prop speed increase=Stiffness increase=Density decrease
Prop speed decrease=Stiffness decrease=Density increase |
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What are the ranges for PRF?
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1000-10,000Hz
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Define PRF.
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Number of electrical pulses per second
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Describe two types of pulse anatomy?
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On time and listening time
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What are the 2 formulas for pulse duration?
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pd=p*n
pd=n/f |
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What is the typical range for pulse duration?
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.5-3 microseconds
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What are the units for duty factor and pulsed ultrasound?
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Unitless
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What happens to duty factor when PRP increases?
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DF decreases
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What happens to duty factor when Imaging depth increases?
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DF decreases
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What happens to duty factor when Pulse duration increases?
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DF increases
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What happens to duty factor when PRF increases?
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DF increases
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What are the 2 types of detail resolution?
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Axial and Lateral
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Define Axial resolution.
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The minimum reflector separation necessary to resolve reflectors ALONG a scan line
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Define Lateral resolution.
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The minimum reflector separation necessary to resolve reflectors ACROSS a scan line
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What are the 3 modes of focusing for a mechanical transducer?
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Lens, Curved element, Mirrors
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Define wavelength.
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The length of space over which one cycle occurs
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What is the formula for wavelength?
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wavelenght=c/f
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What 2 things determine a wavelength?
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Frequency and propagation speed
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What does wavelength influence?
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Axial/longitudinal resolution
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If frequencyy is doubled what hapens to the wavelength?
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It is halved
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What are the effects of ultrasound on tissue termed?
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Bioeffects
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What are the 2 types of bioeffects to mammalian tissue?
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Heating and Mechanical
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What are the 3 types of mechanical bioeffects?
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radation force, steaming, cavitation
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What are the units for wavelength?
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mm
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What are the 2 types of cavitation?
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Stable-dosent burst, Transient-Bursts
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The level at which signals are not transmitted through an ultrasound receiver is termed what?
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Rejection
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What is a pulse of ultrasound?
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A few cycles of ultrasound
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What is the formula for pulsed duration?
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pd=n*t
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How lung is the typical pulsed duration?
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.5-3 microseconds
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What is spacial pulse length analogus to?
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wavelength
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Define beam steering.
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Movement of the transducer over the area of interest
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What does lateral resolution equal?
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Beam diameter
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Axial resolution = what?
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spl/2
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Is the following operator adjustable: compensation and rejection?
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Yes
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Is the following operator adjustable: amplification and compensation?
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yes
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Is the following operator adjustable: demodulation and compression
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no
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Is the following operator adjustable: rejection and amplification?
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yes
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Define pixel.
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Unit which imaging information is divided for storage and display in a digital instrument
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Define dead zone.
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Distance between the transducer face and the 1st rod, no image, area very close to the transducer
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Define Aliasing.
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Improper doppler shift information from pulsed wave/color when the doppler shift exceeds the nyquist limit
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Define M mode.
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B mode presentation of changing reflector position, time, motion, and amplitude
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Define B mode
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Information displayed as brightness
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Define matching layer.
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Material attached to the front of a transducer to reduce the reflections at the transducer element
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Define damping material.
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Material attached to the rear of the transducer to reduce the pulse duration
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Define Q factor.
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Recriprical of fractional bandwidth
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Define Linear array.
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Array made of rectangular elements arranged in a line
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Define Sequential array.
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Array of elements which are activated one at a time
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Define Annular array.
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Array of crystals arragned in a circular symmetry.
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Define frequency spectrum.
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The range of doppler shift frequencies present in returning echoes
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What is the equation for: Prop speed?
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C=
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What is the equation for: Intensity formula?
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I(mw/cm2)=P(mw)/A(cm2)
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What is the equation for: spatial pulse length?
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spl=number of cycles*wavelength
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What is the equation for: Impedance formula?
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Z(rayls)=density*prop speed
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What is the equation for: Wavelength?
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Wavelength=c/f
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What is the equation for: Pulse Duration?
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pd=n*t
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Define: Comet tail artifacts.
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A series of closely spaced reverberation echoes
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Define: Grating lobes?
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Additional, weaker beams of sound traveling in directions different from the primary beam
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Define: Slice thickness.
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Also called sectional thickness, Echoes from adjacent tissues filling what should be anechoic
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Define: propagation speed artifact.
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Occurs when the assumed prop speed is incorrect
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Define: refraction.
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Change of sound direction on passing from one medium to another
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Define: reverberation.
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Myltiple reflections
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Define: Beam profiler.
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Device used to record 3D reflection and amplitude information.
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Define: Tissue equivalent phantom.
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Device for testing ultrasound characteristics of tissue. Simulates soft tissue
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Define: Doppler phantom.
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Used to measure doppler
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What is the AIUM 100mm test object?
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A device that contains rod groups to measure axial and lateral resolution, range accuracy, receiver compensation, dead zone, and thurough registration accuracy
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What type of propagation speed errors relate to improper position?
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Section thickness, Speckle, Reverberation, Mirror image, range ambiguity, refraction, grating lobes, speed errors
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What is a type of imaging that relates to the height of the vertical defection?
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A-mode
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What is a type of imaging that relates to time and motion?
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M-mode
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What is a type of imaging that relates to the brightness of the returning echo?
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B-mode
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Define duty factor?
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The fraction of time the pulsed ultrasound is on
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What is the typical duty factor in pulsed echo?
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.1-1.0
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What is the typical duty factor in continuous wave?
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100%
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Define: Attenuation.
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Reductin of power or intensity as sound travels through a medium
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What are the units of attenuation?
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dB/cm/MHz
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What is attenuation coefficient?
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The attenuation that occurs with each cm the sound wave travels
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What is reduced with attenuation?
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Power and intensity
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Describe the piezoelectric effect?
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When electricity is applied the PZT elements converts the electricity into ultrasound pulses
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What is the typical man made crystal used in most transducers today?
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Lead Zirconat Titante (PZT)
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What is a scan converter?
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A device used to reformat echo data into image form for image processing, storage, and display (image memory)
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What is the frequency for ultrasound?
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> 20,000Hz Greater than audible range
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What is infrasound?
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<20Hz Less than the audible range
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What are the frequencies of audbile sound?
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20Hz-20,000Hz
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What is sound?
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A mechanical longitudinal wave
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What is sound made up of?
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Compressions and rarerefractions
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What parameters can a hydrophone measure?
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Amplitude and period; Acoustic pressure output levels, intensities and output indexes
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What parameters are measured by radiation force?
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PRP, Period, PD, and amplitude
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What does in-vivo dentoe?
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Within
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What does in-vitro dentoe?
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Outside
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What is a calorimeter?
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A device used to measure the amount of conversion of heat
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What is a beam profiler?
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A device used to record 3D reflection and amplitude information
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What are the 3 mechanisms of action for ultrasonid bioeffects?
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Heat-Intensity, Radiation force-Exposure time, and Cavitation-mechanical effect to tissue
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What type of intensity does heating depend on?
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SPTP- Spatial peak Temporal peak
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If frequency decreases what happens to the SPL?
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It increases
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What 2 factors would increase ine intensity of a sound beam?
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Increase power, Decrease focusing
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What is Q factor?
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The recriprical of fractional power
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What is optimal Q factor?
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Low
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Qvalue equals what?
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Material prop speed*thickness of the element
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WHat factor is the operating crystal dependant on?
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Thickness of the element and the mediums prop speed
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Define: Doppler effect.
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Change in frequency caused by motion
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Define: Doppler shift.
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The difference between the emitted Frequency and the frequency returning from echoes
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What is variance mode?
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Variance adds green to red to blue progressing from RT to LT across the map for detection of turbulent blood flow
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What is the doppler shift formula?
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FD=2*fo*v*coso/c
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What is snells law?
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The relationship between the incidence and transmission angles
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What does snells law relate to?
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Refraction
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How long is the round trip time for each cm of distance traveled in soft tissue?
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.13 microseconds
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Define: Snell's law.
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The relationship between the incidence and transmission angles
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Define: Huygen's principle.
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Each surface of multiple transducer, diffract producing small waves that join together and form one main energy sound beam
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Define: Rayleigh's principle.
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Scattering caused by RBC
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Define: Poiseulles law.
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Mathematical description of the dependence of volume flow rate on pressure, vessel length and radius, and fluid viscoscity
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Refraction can only occur if you have what 2 factors?
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Oblique incidence, and Different prop speeds
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Define: Period.
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Time per cycle
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Define: PRP.
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Time from the beginning of one pulse to the next
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Define: PRF.
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Number of pulses oer second
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What are the units for: Period
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(ms)
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What are the units for: PRP
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(ms)
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What are the units for: PRF
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(KHz)
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Why do we use coupling gel?
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To provide a good sound path from the transducer to the skin, eliminating the thin layer of air that would reflect the sound
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What does Duplex ultrasound mean?
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Ultrasound that combines gray scale with pulsed wave and continuous wave doppler
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What type of format, beam steering, and beam focusing does the following have: Linear Array.
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Rectangular image, Electronic focusing, Mechanical steering
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What type of format, beam steering, and beam focusing does the following have: Curved Array.
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Convex image, Electronic focusing, Mechanical steering
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What type of format, beam steering, and beam focusing does the following have: Phased array.
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Electronic focusing and steering
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What type of format, beam steering, and beam focusing does the following have: Annular array.
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Sector image, Mechanical steering, Electronic focusing
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What type of format, beam steering, and beam focusing does the following have: Single element.
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Pie shape image, Mechanical focusing and steering; Lens mirror
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Define: Fast Fourier Transform.
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Digital computer implementation of a mathematical technique for obtaining a doppler frequency spectrum
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Define: Autocorrelation.
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Rapid technique used in most color doppler instruments for obtaining mean doppler shift
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What are the units for Doppler?
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(KHz)
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What is the minimum doppler shift?
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.26(Khz)
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What is frequency shift always related to?
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Change in motion
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At what velocity is the Doppler shift equal to zero?
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<10(cm/sec)
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What factors will eliminate ailiasing in Doppler instruments?
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Change angle, Shift the baseline, Lower the frequency, Increase PRF, Use CW Doppler
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What are the 2 types of color doppler?
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B-Dmode
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Define: duplex.
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Something that combines 2 things
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Define: harmonics.
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Frequencies that are even or odd multiples of another commonly fundamental/operating frequency; 2nd operating frequency
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Why is harmonics used?
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Using harmonic frequencies improves the quality of sonographic images
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What is 3-D?
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2-D slice images presented in plane orientation; commonly used for OB
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If the reflector and the source are moving away from each other, what type of Doppler shift will you get?
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Negative doppler shift
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The dependance on Doppler angle is in the form of a waht?
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Cosine
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All of the following may be used as units of amplitude except which: Millimeters, Degrees, Pascals, meters per second
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m/s
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How are the spatial pulse length and the number of cycles in the pulse related?
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Directly related
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What 2 conditions are necessary for refraction to occur at a boundary between two media?
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Different prop speeds and oblique incidence
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When red blood cells move away from a transducer, the frequency of the wave returned from the RBC is what?
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Less than the emitted frequency
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What are the units of impedance?
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Rayls
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What best describes an angle with a measurement of 133degrees?
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Obtuse
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The sonographer increases the depth. Which parameter is decreased?
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PRF
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What is enhancement caused by?
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Weakly attenuating structures
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Which of the following parameters is determined by the medium: Wavelength, Freq, Period?
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Wavelength and Spatial pulse length depend on the sound source and medium
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Which of the following contributes most to total attenuation in soft tissue: Absorption, Reflection, Scattering?
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Absorption
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What are the units of the transmitted intensity of a sound wave?
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W/cm2
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Which of the following statements is true regarding axial resolution artifiacts: Higher quality images are associated with higher numbers, Axial resolution is reported in units of cm3, Numerically axial resolution equals 1/4 the pulse length, or Too few reflectors appear on the image?
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Too few reflectors appear on the image
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Which of the following is considered an acoustic variable: Freq, Period, Power, or Pressure?
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Pressure
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What are the effects of medium upon the ultrasound wave called?
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Acoustic propagation properties
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What is the acoustic velocity in soft tissue?
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1540m/s
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What is the power intensity for the following: 0dB, -3dB, -6dB, -9dB?
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0=100%, -3=1/2, -6=1/4, -9=1/8
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What 3 factors contribute to attenuation?
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Absorption, Scattering, and Reflection
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What is the formula for impedance?
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Density*Prop Speed
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if the relative output power of an ultrasound instrument is calibrated in dB and the operator increases the output power by 20dB, what is the beam intensity increased by?
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100 times
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What is impedance important in?
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Reflection at boundries
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What is the range of Doppler shifts commonly measured in clinical exams?
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-0.01MHz to 0.01MHz
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How are the maximum imaging depth and spatial pulse lenght related?
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Unrelated
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What does the dynamic range of the receiver of an ultrasound instrument refer to?
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The range of echo signal amplitudes that can be processed without distortion
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Two ultrasound transducers are used to perform Doppler exams on the same patient. The exams are identical except that the transducer frequencies are 5 and 2.5. Which frequency will measure the highest Doppler shift?
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5MHz
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A sound wave leaves its source and travels through air. The speed of sound in air is 330m/sec. One second later an echo returns to the source. At what distance from the source is the reflector that produced the echo?
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D=C/2*Round trip time
165meters |
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What can be said of the Doppler shift when the sound beam is normally incident to the velocity of the red blood cells?
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?
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What does the damping material in the transducer do?
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Increase the spatial pulse length
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A sound wave strikes a boundary between two media at a 60degree angle is called what?
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Oblique incidence
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What are the units of attenuation?
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dB
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How are ultrasound frequency and the attenuation coefficient related?
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Directly related A.C.=f/2
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How are spatial pulse length and pulse duration related?
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Directly
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What is the formal name for dispertion of a wave in many different direction after striking a small particle?
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Rayleigh Scattering
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A sound wave that strikes a boundary between two media at a 90degree angle is called?
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Orthogonal/Normal incidence
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At what angles between the sound beam and the direction of motion will the doppler shift be a maximum?
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0 and 180 degrees
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What kind of angle is a measurement of 35degrees?
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Acute
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Negative decibles means the intensity is doing waht?
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Decreasing
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-10dB means the intensity was reduced how much?
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10 times its original value
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In order for reflection to occur when sound strikes a border between 2 media, what must be different for the reflection to take place?
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Different Impedances
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Medium 1 has a density of 9 and a stiffness of 6, Medium 2 has a density of 8 and a stiffness of 6. WHich medium has a lower prop speed?
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Medium 1
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Snells law is a declaration concerning the behavior of waves during a particular physical process or event. what event is this?
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Refraction
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What information does the Doppler shift furnish concerning the blood cells that produce it?
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Velocity
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What is the location where the sound beam reaches its narrowest diameter known as?
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The focal zone
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An ultrasonic pulse is traveling in soft tissue, which of the following is most important in determining the frequency of the sound contained in the pulse: The prop speed of the transducers matching layer, The thickness of the transducers backing material, The impedance of the transducers matching layer, or The prop speed of the transducers active element?
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The thickness of the transducers active element
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By changing the imaging depth, which of the following does the operator also change: PRF and PRP, SPL, prop speed, or PD
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PRP and PRF
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Which of the following parameters is affected by the medium: PRP, SPL, DF, or PD
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SPL
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All of the following are determined solely by the ultrasound machine except which: PD, freq, SPL, or Period?
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SPL
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How are the maximum imaging depth and PRP related?
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Directly related
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The sonographer decreases the depth. Which of the following parameter is decreased: PRP, PRF, Resonance Freq, or non of tthem?
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PRP
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What is the Doppler effect presented when the source and the receiver are moving closer together or further apart?
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Frequency shift
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Doppler shift produces information about what?
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Velocity
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At what angle between the sound beam and the direction of motion will the Doppler shift be absent?
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90degrees
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If a red blood cell is traveling ttoward a transducer, the frequency emitted by the transducer is what compared to the frequency reflected from the RBC?
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Less than
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In standard Doppler, what is known about the reflected frequency produced by RBCs traveling in a direction away from the transducer: It is in the audible range, It is ultrasonic, Its greater than the transmitted frequency, or its less than the transmitted frequency?
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Its ultrasonic
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The Doppler shift does not always provide a valid estimate of the speed of the RBCs that produce it because the **** is related to what?
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The Cosine of the angle between the direction of the beam and the direction of blood flow
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An artifiact produced by interference patterns and resulting in the granular appearance if images is termed what?
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Speckle
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When creating an ultrasound image, all of the following assumptions are made Except which: Sound travels in a straight line, Sound travels at 1.54mm/microsec, Reflections only arise from structures in the pulses main beam, The sound beam is extremely thin, or All structures create reflections of equal magnitude?
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All structures create reflections of equal magnitude is false
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You have obtained an ultrasound image that demonstrates refraction of the sound beam, this artifact might be manifested as what?
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Lateral displacement of a reflector
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Define: Doppler frequency.
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The difference between the transmitted and received frequencies
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You have placed the Doppler sample volume in a vessel that is 3cm deep. How long will it take the reflected signal to arrive back at the transducer?
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39microseconds
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You are performing a venous ultrasound exam with a 5MHz linear array transducer using a single focal zone. Where is the thinnest width of the beam in the z-axis
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At the point of mechanical focusing
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Which of the following statements is true about lateral resolution: It is also called angular, transverse, and depth resolution, It is reported in units of time, It is the same at all depths, or it can be improved by focusing?
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It can be improved by focusing is true
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All of the following artifacts result in the placement of too many echoes on the image Except which: Shadowing, Reverberation, Mirror image, or Grating lobes?
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Shadowing
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At what point does ailiasing occur?
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When the frequency exceeds 1/2 the PRF
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Which of the following artifcat is associated with resonance of a gas bubble: Grating lobes, Comet tail, Acoustic speckle, Ring down, or Refraction?
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Ring down ie.-bowel
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You are imaging a patient with a thickened gallbladder wall. In what direction can the the wall thickness be measured most accurately?
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Perpendicular to the beam axis
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What is the source of the enhancement artifact?
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Decreased attenuation through a weakly attenuating structure
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Which of the following does not result from multiple reflections: Comet tail, Reverberations, Ring down, or Enhancement?
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Enhancement
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What are the units for measuring the volume of a sphere?
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cm3
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If you measure the distance around the perimieter of a structure, you are measuring what?
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Its circumfrence
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You are using a transducer that produces a beam with a very wide slice thickness. Which of the following problems are you most likely to encounter: Increased near field reverberations, Increased side lobes, Decreased penetration, Partial volume artifact, or Increased electrical interference?
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Partial volume artifact
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What does the range equation describe?
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The relationship between round-trip pulse travel time and distance to reflector
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Which of the following artifacts commonly fills in small linear vessels: Refraction, Partial volume, Mirror image, Range ambiguity, or multipath artifact?
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Partial volume artifact
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