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87 Cards in this Set
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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= [(Z2Z1)/(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?

23

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?

0.21mm

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
