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92 Cards in this Set
- Front
- Back
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Bandwidth
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the range of frequencies between the highest & lowest frequencies sent from the transducer.
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what is rejection
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eliminates low amplitude echoes but doesn't effect high amp echoes
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what is the Bernouli Principal?
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an increase in velocity makes a decrease in pressure. (Airplane taking off)
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What is compression?
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decreasing the differences between smallest and largest echo amps to a usable range.
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Amplification means
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the conversion of small voltages into larger voltages
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what is the formula for wavelength?
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=prop speed/frequency (C/F)
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what is the formula for PRP?
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1/PRF
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Define Wavelength?
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the length of space that 1 cycle takes up.
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define spatial pulse length?
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the length of space a pulse takes up
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what is a transducer?
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any device that converts 1 form of energy into another.
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what is an accustic speckle?
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Interference pattern gives a grainy image
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what is the formula for near zone formula?
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f x d (sq) / 6
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what is the formula for period?
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1/f
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what is the formula for pulse duration?
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nt or n/f
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What is the formula for temporal average?
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pa/df
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what is the power ratio formula?
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(VR)sq
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What is voltage ratio?
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the ratio of output to input. OP/IP
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What is the formula for Impedance?
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d/c (density x prop speed)
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what is the formula for intensity reflection coefficient?
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((Z2-Z1)/(Z2+Z1)) sq
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what is amplitude
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the max variation in an acoustic variable. How far away it gets from normal values.
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what is the windkessel effect?
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expand/contract of compliant vessels. Valves that stop back flow & cause extended flow.
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explain Doppler shifts.
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fires 2 pulses @ RBC (in the beam) when they come back the computed difference in frequency is the shift. Finds the distance traveled.
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what is the formula for flow rate?
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PD/LV (pressure x diameter/length x viscosity
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What is sound?
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a mechanical longitudinal wave that back and forth particle motion is parallel to the direction of travel.
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What is the attenuation formula?
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1/2FL (1/2 x frequency x path length)
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What is the formula for distance?
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1/2CT (1/2 x prop speed x time)
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What is the formula for Quality Factor?
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OF/B (operating freq/bandwidth)
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What is the intensity formula?
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P/A (power/area)
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What is the formula for ITC?
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1-IRC
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What is the formula for Duty Factor?
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PD/PRP (pulse duration/ pulse rep period)
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What is duty factor?
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The fraction of time that pulsed U/S is on.
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What is PRF?
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The # of pulses in 1 sec
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What is sound?
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A traveling variation in wave variables.
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What is frequency?
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The # of cycles in 1 sec.
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What is optimum frequency?
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Highest frequency used that has sufficient penetration.
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What is period?
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The time it takes for one cycle to occur?
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What is Temporal Resolution?
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The ability to accurately locate moving structures @ any given instance in time.
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What is dynamic Range?
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ratio of largest to smallest amplitude (power) that a system can handle.
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What is compensation?
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images are uniformed brightness from top to bottom.
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How do you correct the effects of attenuation?
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Compensation
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What is apodization?
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Creation of grating lobes due to multiple elements.
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How do you reduce apodization?
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Varying drive voltage on outer elements of array.
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What is pixel interpolation?
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Assigns a brightness value on the average of brightness of adjacent pixels.
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What is elastography?
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Usually in color, shows how stiff the tissue is.
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What is flow rate?
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The volume of blood passing a point per unit of time.
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What is persistence?
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Frame averaging of sequential frames to make a smoother image & reduce noise.
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What is IRC?
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How much gets sent back. % bounced back.
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What is ITC?
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How much gets through.
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Define the Doppler effect?
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A change in frequency (& wavelength) due to motion.
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What is the formula for Impedance Density?
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m/v (mass/volume)
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What is pulse duration?
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The time it takes for 1 pulse to occur.
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What is quality factor?
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A unitless # that represents the extent of damping. (how much it is damped)
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What is range ambiguity?
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for each pulse all echoes are received before the next pulse is sent (max depth is determined by PRP)
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What is SPL?
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The ability to see 2 items above & below each other as separate items.
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What is pre-amplification?
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amplified in transducer (thick wire-low res/this wire-high res)
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What is the formula for fractional bandwidth?
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B/OF (bandwidth/operating freq)
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What is the rule for 3D tubes?
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If the diameter goes down by 1/2, then speed goes up by a factor of 4.
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What is the formula for frequency?
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c/w & 1/t ( speed/wavelength or 1/time)
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What is the formula for Intensity Duty Factor?
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TA/PA (Temporal Avg/Pulse Avg)
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What is the focal region?
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an area on either side of the focal point that is within 25% or 6 db of the SPI (spatial Peak Intensity)
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What is oblique incidence?
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Direction of travel that is not perpendicular to boundary between 2 media.
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What is hydrostatic pressure?
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The weight of blood pressing against vessels from level of heart to level of measurement.
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What is amplification?
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Converts small volts to larger volts to process & store. aka GAIN
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What is pulsatile flow?
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non steady flow that result from acc/dec of cardiac cycle.
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What is the formula for PRF?
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1/PRP
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What is the Doppler effect?
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Change in frequency of sound as a result of motion between source and receiver.
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What is demodulation?
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Takes the difference in freq of the shift from transducer freq. It knows if the received pulse is @ different freq something has motion.
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What is pressure?
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force per unit area.
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What is turbulent flow?
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Flow is random or reversed. Can be heard, happens distal to stenosis.
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What is power?
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the rate that energy is transferred from 1 location to another
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What is impedance?
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determines transmission or reflection of waves. Measure of down stream resistance.
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What is refraction?
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a change in the direction of sound when it crosses a boundary.
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What is scattering?
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the redirection of sound in many directions by rough surfaces or heterogeneous media.
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What is the formula for axial resolution?
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1/2 SPL ( 1/2 Spatial pulse length) 1/2 nw, or 1/2 nc/f
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What is pressure?
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force per unit of area, = distributed in static fluid uniformly
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What is Piezoelectric effect?
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When a certain materials create a voltage when pressure is applied or when the material is mechanically deformed.
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What is the Doppler effect?
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a change in echo frequency
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What is viscosity?
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The resistance to flow by a fluid in motion. Units are poise. (Thickness of a fluid)
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What is PRP?
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The time from beginning of one pulse to the beginning of the next. (includes listen time)
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What is attenuation?
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A weakening of sound as it propagates.
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What is magnitude?
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Strength of the sound.
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What is pulse avg (PA)?
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Intensity averaged over pulse duration. (how much for how long)
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What is back scatter?
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Sound scattered back in the direction from which is originally came.
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What is speed (velocity)
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The rate @ which an object covers a distance.
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What is area?
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The amount of material involved
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What is intensity?
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The rate energy passes thru a unit area of the beam. Concentration of power in the beam.
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What is energy?
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the ability to do work.
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What is propagation speed?
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the speed with which an entire wave moves through a medium.
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What is SPW?
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The ability to see 2 items side by side as separate.
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Electric scanning sequencing
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fires small groups of elements in sequential order in a straight line. No steering (linear & curved array)
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What is the range equation?
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1/2ct
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What is the Doppler shift equation?
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2VCosOFo/C (2 x Velocity x Cosine angle x orig freq/speed of sound in ST
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