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87 Cards in this Set
- Front
- Back
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Give the formula for propagation speed
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C= frequency * wavelength
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Propagation speed is dependent on what?
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The medium
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If density increases what happens to the propagation speed?
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decreases
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Give the formula for wavelength
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wavelength= c/ frequency
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give the units for frequency
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Hz or MHz
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Give the units for Period
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seconds or microseconds
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Give the units for wavelength
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meters or millimeters
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Give the units for propagation speed
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m/sec or mm/microsecond
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Give the units for PRF
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H or kHz
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Give the units for PRP
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seconds or microseconds
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Give the units for Pulse Duration
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seconds or milliseconds
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Give the units for Duty Factor
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Duty factor is unitless!
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Give the units for SPL
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millimeters
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Give the units for Amplitude
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Megapascals (MPa)
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Give the units for Power
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Watts or milliwatts
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Give the units for Intensity
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watts/cm^2
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Give the units for the Beam Uniformity Ratio (BUR)
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BUR is unitless!
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Give the units for Attenuation
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Decibels
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Give the units for the attenuation coefficient
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dB/cm
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Give the units for Impedence
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Rayls
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Give the formula for SPL
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SPL= n * wavelength
OR SPL= (n*c)/frequency |
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Give the formula for Pulse Duration
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PD= n * T
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Give the formula for Duty Factor
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DF= (PD/PRP) * 1000
OR DF= (PD*PRF)/1000 |
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Give the formula for Intensity
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Intensity= Power/Area
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Describe the Temporal average intensity to the Peak average intensity
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Intensity TA = Intensity PA * DF
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Give the formula for Beam Uniformity Ratio
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BUR= SP/ SA
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Give the formula for Attenuation coefficient
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Ac= 1/2 frequency
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Give the formula for Attenuation
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Attenuation= Ac * Length
OR Attenuation= 1/2frequency * length |
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Give the formula for the Half Value Thickness Layer
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HVTL = 3/ Ac
OR HVTL = 6/ frequency |
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Give the formula for Impedence
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Z= density * c
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Give the formula for the Intensity Reflected Coefficient
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IRC= [(Z2-Z1)/(Z2+Z1)]^2
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Give the formula for the Intensity Transmitted Coefficient
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ITC= 1- IRC
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Give the formula for Snell's Law
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[sine incident angle/ sine transmitted angle]= c1/c2
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Give the formula to solve for the distance of the reflector
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D= 1/2 [c * time]
t represents round trip time |
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The average round trip distance of a reflector can be solved using which rule?
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13microseconds/1cm Rule
aka the rule of 13 |
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Define frequency
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number of cycles per second
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Define period
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time it takes for one cycle to occur
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Define wavelength
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The length of one complete cycle
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Define PRF
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the number of pulses per second
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Define PRP
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Time from the begin of one pulse to the beginning of the next pulse
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Define PD
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time it takes for one pulse to occur
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Define Duty Factor
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Fraction of time the transducer is generating a pulse (when it's on)
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Define SPL
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Length of a pulse
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Define Amplitude
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Variation of a given sound wave, indicates strength
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Define Power
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Rate at which energy is transferred
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Define Intensity
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Rate at which energy passes through an area
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Define the Beam Uniformity Ratio
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unitless ratio that describes the distribution of the sound beam intensity
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Define Attenuation
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weakening of a sound beam
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Define the Half Value Thickness Layer
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distance intensity must travel to be reduced by half the original intensity
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Define Backscatter
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sound travels back in the direction it came from
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How many pulses are in a pulsed wave cycle?
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2-3
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How many pulses are in a Doppler wave cycle
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5- 30
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Describe the relationship between power, intensity, and amplitude
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Power is congruent to Intensity
Power is congruent to Amp^2 Intensity is congruent to Amp^2 |
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Describe the purpose of Focusing a beam
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Decreases the area of the sound beam therefore increases the intensity
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Where is the Spatial Peak intensity found
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At the beam center
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What is the most common intensity used in pulsed wave?
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SPTA
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Where is SPTP used?
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In continuous wave, is the highest intensity
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What is the purpose of a hydrophone?
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measures the intensity of a sound beam
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When does a specular reflection occur?
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When the wavelength is larger than the boundary and the surface is smooth
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What kind of boundary does perpendicular incidence encounter?
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A 90 degree angle
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What kind of boundary does an oblique incidence encounter?
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Any angle other than 90 degrees
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Give the 3 criteria for Snell's Law
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1. need 2 different c
2. need to hit at oblique angles 3. incident angle = reflected angle |
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Give the 2 requirements for Refraction to occur
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1. oblique incidence
2. different propagation speeds on each side of the boundary |
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Refraction is strongly dependent on?
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Impedence
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What will cause scattering?
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1. size of reflector is equal or less than the wavelength
2. a rough surface |
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List the contrast agents used in the U.S
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1. Definity
2. Imagent 3. Optison |
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What are the purposes of contrast agents
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1. improve lesion detection
2. improves weakened Doppler signals |
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List the acoustic variables
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1. Pressure
2. Density 3. Particle vibration |
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Give the formula for NZL
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NZL= (apeature)^2/(4*wavelength)
OR NZL= (aperature)^2*freq/4*c |
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Give the formula for Q Factor
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Q= operating freq./ Bandwidth
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What is the purpose of damping material?
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used to reduce number of cycles in a pulse to improve resolution
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What is sacrificed with damping material
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sensitivity
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What is the damping material composed of?
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epoxy resin and metal powders
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What is another name for damping material?
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Backing material
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How thick are ultrasound elements typically?
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0.2-1mm
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Describe the relationship between crystal thickness and frequency
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The thicker the crystal the lower the frequency
The thinner the crystal the higher the frequency |
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Describe the matching layer in relation to the crystal wavelength
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matching layer = 1/4 wavelength of the crystal
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What determines the Near Zone Length?
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aperature and operating frequency
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What is another name for near zone?
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Fresnel zone
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Describe the relationship between NZL, aperature, and frequency
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Increase aperature, increase NZL
Increase frequency, increase NZL |
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What is another name for the far zone?
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Fraunhofer zone
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Describe the width of the transducer element at the end of the NZL and at double the NZL
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End of NZL beam width= 1/2 transducer element width
Double NZL beam width = transducer element width |
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Focusing can only be accomplished in what zone?
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Fresnel zone aka near zone
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Annular array transducers are __ steered and __ focused
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mechanically steered, electronically focused
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Define aperature
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Size of the ultrasound element
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Define apodization
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outer elements are driven at lower amplitudes than inner elements to reduce grating lobes
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Define matching layer
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Placed in front of transducer to reduce reflection at the transducer/element interface
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