Ouhsc Physics Test 2

Front 1

what afre the ranges in the acoustic spectrum

Back 1

<20 Hz Infrasound
20Hz - 20,000 Hz Audible Sound
20,000Hz - 1 MHz Ultrasound
1MHz - 30 MHz Diagnostic Medical Ultrasound

Front 2

what are the ranges in the acoustic spectrum

Back 2

<20 Hz Infrasound
20 - 20,000 Hz Audible Sound
20,000Hz - 1 MHz
Ultrasound
1MHz - 30 MHz Diagnostic Medical Ultrasound

Front 3

theses respresent areas of no displacement

Back 3

nodes

Front 4

these respresent areas of no displacement

Back 4

nodes

Front 5

these represent areas of maximum displacement

Back 5

anti-nodes

Front 6

theses respresent areas of maximum displacement

Back 6

anti-nodes

Front 7

what is the average velocity of sound in soft tissue

Back 7

1540 m/s

Front 8

what is the average velocity of soundin soft tissue

Back 8

1540 m/s

Front 9

what effects velocity more, density of stiffness

Back 9

stifness, represented by the bulk modulus

Front 10

what effects velocity more, density of stiffness

Back 10

stifness, represented by the bulk modulus

Front 11

this is a measurement of the stiffness in a tissue

Back 11

bulk modulus

Front 12

this is a measurement of the stiffness in a tissue

Back 12

bulk modulus

Front 13

what kind of relationship do compressibility and velocity have

Back 13

they are inversely related

Front 14

what kind of relationship do compressibility and velocity have

Back 14

they are inversely related

Front 15

what is the formula for intensity

Back 15

I=power/area

Front 16

what is the formula for intensity

Back 16

I=power/area

Front 17

what units are intensity measured in

Back 17

W/m(E2)
or
W/cm(E2)
or
mW/m(E2)
or something of that nature

Front 18

what units are intensity measured in

Back 18

W/m(E2)
or
W/cm(E2)
or
mW/m(E2)
or something of that nature

Front 19

If there are 100 Watts in an area of 10 centimeters, what is the intensity

Back 19

100W/10cm(E2) =
10 W/cm(E2)

Front 20

If there are 100 Watts in an area of 10 centimeters, what is the intensity

Back 20

100W/10cm(E2) =
10 W/cm(E2)

Front 21

calculate the decibels for audible sound if there is 100 watts of power in an area of 10 cm

Back 21

100 W/10cm(E2) = 10W/cm(E2)

10log(I/Io)

10log (10W/cmE2) / (10 E-12W/m E2)

must convert the denominator to cmE2

10log (10W/cmE2) / (10E-12W/cmE2)

130 dB
(I dont know if this is all correct, he didnt give an answer)

Front 22

what do watts measure

Back 22

joules/sec

Front 23

what are the two refrence intensities

Back 23

10 E-12 W/mE2
10 E-16 W/cmE2

Front 24

1 mile = how many ft

Back 24

5280 ft

Front 25

what is the formula for finding period

Back 25

T=1/frequency

Front 26

if you know the period what is the formula for finding frequency

Back 26

frequency = 1/T

Front 27

Tera is.....

Back 27

T
10E12
1,000,000,000,000

Front 28

Giga is.......

Back 28

G
10E9
1,000,000,000

Front 29

Mega is.....

Back 29

M
10E6
1,000,000

Front 30

Kilo is......

Back 30

k
10E3
1,000

Front 31

Hecto is......

Back 31

h
10E2
100

Front 32

Deca is......

Back 32

da
10E1
10

Front 33

Deci is......

Back 33

d
10E-1
.01

Front 34

Centi is......

Back 34

c
10E-2
.001

Front 35

Milli is....

Back 35

m
10E-3
.0001

Front 36

Micro is.....

Back 36

stupid little jacked up "u" sign
10E-6
.000 001

Front 37

Nano is.....

Back 37

n
10E-9
.000 000 001

Front 38

Pico is......

Back 38

p
10E-12
.000 000 000 001

Front 39

what is a compression

Back 39

area with the highest density of molecules (top)

Front 40

what is a rarefaction

Back 40

area with the lowest density of molecules (bottom)

Front 41

this is a mechanical wave that exists in the physical movement of vibrating molecules

Back 41

soundwave

Front 42

what is velocity and what is its symbol

Back 42

it is a measurement of meters per second

c

Front 43

what is frequency, what is its symbol, and what is it measured in

Back 43

cycles per second

(its symbol is that stupid jacked up lookin "v" that my computer wont make cause its a piece)

measured in Hz

Front 44

what is period, what is its symbol, and what is it measured in

Back 44

time it takes for a cycle to occur

T

measured in seconds

Front 45

what is wavelength, what is its symbol, and what is it measured in

Back 45

measurable distance from crest to crest

lambda is its symbol

measured in meters

Front 46

what is the unit for intensity

Back 46

watts

Front 47

what is a sine wave a graph of

Back 47

pressure variation

Front 48

what is the ultrasound reference intensity for soft tissue

Back 48

1540 m/s

Front 49

as compressibility increases, what happenes to velocity

Back 49

decreases

Front 50

a transducer converts one form of energy into another with a fixed relationship between _____ and _____

Back 50

input energy and output energy

Front 51

a microphone is an example of a transducer that changes what type of energy in to what type of energy

Back 51

changes mechanical sound energy into an electrical signal

Front 52

a loudspeaker is an example of a transducer that changes what type of energy into what type of energy

Back 52

electrical signal into a mechanical sound wave

Front 53

an ultrasound transducer converts what type of energy into what type of energy

Back 53

electric energy into ultrasound energy and also converts electrical energy into mechanical energy. this is why it is used as both the transmitter and the reciever

Front 54

Mr. Bad Ass Curie found that when a _______ force was applied perpendicular to a quartz crystal, it produced an ______ charge . He also found that when an _______ signal was applied to the crystal it would vibrate and produce a _______ signal. What effect is this describing

Back 54

mechnaical
electrical
electrical
mechanical
(this is why the transducer can be used as both the transmitter and reciever). This is describing the piezoelectric effect

Front 55

how would you polarize a transducer

Back 55

1. heat the ceramic element to hotter then its curie point
2. apply voltage to the element. this causes the diploes to align
3. cool the element to below its curie point, then remove the voltage

Front 56

what is curie point

Back 56

the temperature at which a crystal loses its piezoelectric properties

Front 57

most of the naturally occurring material in transducers have been replaced by what

Back 57

piezoelectric ceramic transducers

Front 58

a transducer is most efficent at converting energy at its_______

Back 58

resonance frequency

Front 59

this is the frequency at which the crystals in a transducer vibrate

Back 59

resonance frequency

Front 60

resonance frequency is determined by the......

Back 60

size and thickness of the crystal

Front 61

resonance frequency occures most efficiently when.......

Back 61

the thickness of the crystal is 1/2 of the wavelength

Front 62

calc the resonance frequency if the crystal is 2mm thick and has a velocity of 1540m/s

Back 62

2mm x 2 = 4mm
4mm = 4x10E-4m

c=(frequency)(wavelength)
frequency= c/wavelength
frequency= (1540m/s) / (4x10E-3 m)

frequency= 3.8 x 10E5 Hz

Front 63

inside the transducer on the back of the crystals there is a conducting film that functions to .......

Back 63

transmit electric current from the cable to vibrate the crystals

Front 64

interfaces with air, how much of the acoustic impeadence comes back

Back 64

almost 100%

Front 65

what part of the transducer stops the reflected soundwave from coming back and hitting the crystals again

Back 65

the backing

Front 66

if the transducer had no backing material, and the reflected soundwave came back and hit the crystals we would have _______

Back 66

interference

Front 67

in a transducer with no backing, if the reflected wave came back and hit the crystals again, and it was in phase, what would this mean

Back 67

the two wave peaks (intended wave and reflected wave) would line up and cause constructive interference

Front 68

in a transducer with no backing, if the reflected wave came back and hit the crystals again, and it was out of phase, what would this mean

Back 68

the two wave peaks (intended wave and reflected wave) would not line up and it would cause destructive interference

Front 69

what are the 2 purposes of the backing material

Back 69

1. dampens the sound to create short pulses (aka short resonance frequency)
2. to get rid of the air behind the crystal so we dont have a large reflection of sound causing interference

Front 70

why do we add the plastic cover on the front of the transducer

Back 70

it gives us an acoustic impedance matching layer. this is needed because the acoustic impedance of the PZT transducer is 20 times greater than that of the soft tissue. at areas where the acoustic impedances are different we get reflection, but at areas such as the patients skin, we dont want reflections (thats why they slap that KY all up on ya). so they put a quater wavelength matching layer (aka, the acoutic impedance matching layer) on the front of the transducer. it basically tricks the beam into thinking it has the same impedance as the trasducer so we dont get a bunch of reflection

Front 71

what does the quarter wavelength matching layer do

Back 71

it basically tricks the beam into thinking it has the same impedance as the transducer, so we dont get a bunch of reflection

Front 72

what does the quarter wavelength matching layer mean

Back 72

it means the thickness of the plastic on the front of the transducer is 1/4 of the wavelength

Front 73

what happens when we have an interface between two tissues that have different acoustic impedances

Back 73

we get reflection

Front 74

what s the formuls for calculating the amplitude reflection coefficient

Back 74

R=(Z2 - Z1) / (Z2 + Z1)

Front 75

With the amplitude reflection coefficient, Z1 is the _______ and Z2 is the _______

Back 75

proximal impedance (first tissue)
distal impedance (second tissue)

Front 76

How would you figure out what percent of the acoustic energy has been reflected at a certain interface

Back 76

calculate the amplitude reflection coefficient and multiply your answer by 100

Front 77

short pulses have a ______ bandwidth

Back 77

broad

Front 78

we dampen the crystal so we get short pulses and what kind of frequencies

Back 78

a range of frequencies. if we didnt dampen the crystal we would get a single frequency instead of a range of frequencies

Front 79

if we didnt dampen the crystals we would get _______ pulses with ______ bandwidths

Back 79

long pulses with short bamdwidths

Front 80

we measure bandwidth at......

Back 80

full width and half max (aka, 50% of the peak)

Front 81

what are pulses

Back 81

how long a sound lasts (not cycles per second)

Front 82

what is the formula for finding pulse durations

Back 82

PD= (N) (T)
N is the number of cycles
T is the period (time it takes to complete one cycle)

Front 83

why do we want short pulse durations

Back 83

we need short pulse durations in order to imprive our axial resolution

Front 84

why do short pulse durations improve axial resolution

Back 84

if the echos arrive back at the transducer farther apart in time than the pulse durations, we can discriminate between them.

Front 85

if a pulse duration is 1 microsecond and 2 pulses arrive back at the transducer farther apart than 1 microsecond, could we resolve them

Back 85

yes

Front 86

if the time gap between two returning echos is greater than the pulse duration, the echos will be distinguishable or undistinguishable

Back 86

distinguishable

Front 87

With lateral resolution, the returning echos must be separated more laterally than the ......

Back 87

width of the beam

Front 88

what is impedance measured in

Back 88

rayls

Front 89

what is the amplitude reflection coefficient unit (what is it measured in)

Back 89

no unit. impedance is measured in rayls, but they cancel each other out

Front 90

what is a specular refelctor

Back 90

a large smooth reflector (when we say large we mean an area larger than the wavelength)

Front 91

in order to see reflection we need what kind of an angle

Back 91

perpendicular with no more than a 3 degree variation in either direction

Front 92

this is a change in the direction of the sound beam at the interface

Back 92

refraction

Front 93

this occurs when the incident beam is not perpendicular and the velocity of the sound is different on both sides of the interface

Back 93

refraction

Front 94

what two qualities must a beam possess in order for us to say it has been refracted

Back 94

not a perpendicular angle and the velocity of sound must be different on both sides of the interface

Front 95

if a beam hits two tissues with different velocities at an incident angle of 90 degrees, would we have refraction?

Back 95

no. it has to have 2 diff velocities and not be at 90 degrees

Front 96

give the formula for Snells Law

Back 96

sin of incident angle/ sin of refracted angle = incident velocity / refracted velocity

Front 97

if you have an incident angle of 45 degrees, an incident velocity of 1580 m/s, and a refracted velocity of 1475, what would your refracted angle be?

Back 97

41.4 degrees

Front 98

what do we get when we have a rough suface instead of a large smooth surface (specular reflector)

Back 98

scatter

Front 99

what kind of reflection is scatter

Back 99

diffuse reflection

Front 100

what are the pros and cons about scatter

Back 100

pro-more echos going back to transducer to be detected

con-with specular reflection the reflected beam still has 100% of its energy. With scatter of diffuse reflection the energy of the reflected beam is not divided up between so each beam is weaker

Front 101

as our soundwave passes through tissue, some of it is absorbed. what does this describe

Back 101

attenuation

Front 102

is a denser tissue more likely to be heated than a less dense tissue

Back 102

shit yeah

Front 103

the absorption coefficient for bone is ___ times greater than tissue

Back 103

30

Front 104

the amount of heating casued by attenuation is limited by what 2 things

Back 104

conduction and vascular perfusion

Front 105

give an example of conduction

Back 105

when a beam is attenuated by bone and heated up, the heat is dispersed into the surrounding tissues

Front 106

explain vascular perfusion

Back 106

as tissue is heated up by a beam, the blood in your vascular system can absorb some of the heat and carry it away (like the cooling systim in my G ride Bentley)

Front 107

what are the two biological effects of heating on the tissue

Back 107

conduction and vascular perfusion

Front 108

although we prefer to use high frequency, what problems can it cause

Back 108

high velocity increases attenuation, which increases the chance of biological effects

Front 109

what are the biological effects of ultrasound

Back 109

heat and cavitation

Front 110

when dealing with refraction, when you go from slow to fast your refracted angle (from the x axis) gets _______

Back 110

larger

Front 111

when dealing with refraction, when you go from fast to slow your refracted angle (from the x axis) gets _______

Back 111

smaller

Front 112

with refraction is there any energy lost

Back 112

no

Front 113

with reflection is there any energy lost

Back 113

yes

Front 114

with scettering is there any energy lost

Back 114

yes

Front 115

what are the 3 things that constitute attenuation

Back 115

reflection
scattering
absorption

Front 116

attenuation is measured in ______

Back 116

dB/cm
(as a beam goes through 1 cm of tissue, it loses x amount of decibels

Front 117

Increasing the frequency ________ the pulse durations. Increasing the frequency will ______ the period. If you decrease the period you will _____ the pulse durations

Back 117

increasing frequency reduces PD
increasing frequency decreases the period
decreasing the period decreases the PD

Front 118

As you increase the frequency you are doing what to attenuation. Consequently, when you incease attenuation more energy in your beam is lost, which means you have more energy being deposited in ______

Back 118

increasing attenuation
into your shallow tissues and not reaching the deeper tissue

Front 119

what is the first biological effect of ultrasound

Back 119

heat

Front 120

what is the second biological effect of ultrasound

Back 120

cavitation

Front 121

what are the 2 types of cavitation

Back 121

stabel caviation and transient cavitation

Front 122

what is stable caviation

Back 122

when the bubbles exapand and contract synchronously with the presssure oscillations of the beam. the expansion and contraction causes additional stress on the tissues

Front 123

what is transient cavitation

Back 123

where the pressure and temp inside the cavitation bubbles has increased enough to the point where they will break

Front 124

the temp inside the cavitation bubbles can reach temperatures of _______

Back 124

+1000 degrees

Front 125

what kind of problems does the collapse of the transient bubbles cause

Back 125

mechanical disturbances (shock waves)
the temp inside the bubbles can get hot enough to cause free radicals

Front 126

why is there no potential risk of biological damage to the ultrasound tech

Back 126

the air between your hand and the transducer reflects 100% of the beam