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87 Cards in this Set

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