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Ambers Physics 1 > Particle Motion & Wave Propagation > Flashcards

Particle Motion & Wave Propagation Flashcards

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1
Q

What are the 5 steps of a sonographers job?

A 
1- operator control 
2- transducer activation (sending)
3- sound interaction 
4- transducer activation (receiving) 
5- image display
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2
Q

Describe operators control

A

Operator (sonographer) decides which transducer and preset to use based on requisition and patient history

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3
Q

Describe transducer activation (sending)

A

Electrical current is sent to transducer and converted into sound through “reverse piezoelectric effect”

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4
Q

Describe sound interaction

A

Sound waves travel through tissue and produce echos that return to transducer

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5
Q

Describe transducer activation (receiving)

A

Returning sound waves are converted back into electrical current through “piezoelectric effect”

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6
Q

Describe image display

A

Electrical current is processed through the machine and converted into an image on a monitor

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7
Q

What is the Piezoelectric effect

A

Pressure waves are applied to certain crystals which produce electrical pulses (voltage)

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8
Q

What is the reverse piezoelectric effect

A

When electrical pulses (voltage) are applied to certain crystals which produce sound waves

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9
Q

What is Attenuation

A

Weakening of sound waves

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10
Q

What is Acoustic

A

Refers to sound

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11
Q

What is propagation

A

Refers to travel

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12
Q

What is acoustic propagation

A

Refers to the effects tissues cause on sound

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13
Q

What are bioeffects

A

Refers to the effects of ultrasound on tissue

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14
Q

Is sound a propagating variation (a wave)

A

Yes

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15
Q

Do waves carry matter or energy ?

A

Energy

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16
Q

What type of wave needs a medium to travel?

A

Mechanical wave

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17
Q

What are the qualities of waves called?

A

Variables

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18
Q

What are the 4 acoustic variables of sound when it travels through a medium?

A

1- pressure
2- density
3- particle motion
4- temperature

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19
Q

How can pressure be expressed on a sine wave?

A

Crests - increased pressure

Troughs - decreased pressure

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20
Q

In regards to pressure, when particles vibrate when is there high pressure, when is there low pressure?

A

High pressure - when particles are close together

Low pressure - when particles are farther apart

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21
Q

What is density ?

A

Density is the concentration of particles or mass per unit volume

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22
Q

Regions of low density are called?

A

Rarefactions

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23
Q

Regions of high density are called?

A

Compressions

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24
Q

List the two parts of temperature related to sound

A

Sound is an energy

Energy creates heat

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25
Q

Sound is what type of wave?

A

A mechanical wave

needs a medium to travel through, can’t travel through space

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26
Q

List some types of mechanical waves

A

Sound
Transverse
Rayleigh
Longitudinal

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27
Q

List some types of NON mechanical waves

A

Gamma rays
X rays
Light

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28
Q

Describe longitudinal waves

A

Particles motion is the same direction (parallel) to the direction of the wave

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29
Q

Describe transverse waves

A

Particles motion is perpendicular to waves motion

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30
Q

What type of wave is used in ultrasound

A

Longitudinal mechanical wave

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31
Q

Solids, liquids, gases support which type of wave?

A

Longitudinal
(Best in solid and liquid)
(Worst in gas)

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32
Q

Only solids support which type of wave?

A

Transverse

33
Q

What is mode conversion?

A

One type of wave is converted into another form.

34
Q

What is frequency? What is it’s units?

A

Cycles per second
(number of complete variations an acoustic variable goes though in one second)

Hz
(Ultrasound uses MHz)

35
Q

What is period? What is it’s units?

A

The time it takes for something to complete one cycle

Seconds - s
Ultrasound it is measured in microseconds - us

36
Q

What is a wavelength and what is it measured in?

A

Wavelength is the length of space one cycle takes to be completed

Usually measured in millimetres - mm

37
Q

If frequency increases what happens to period and wavelength?

A

If frequency increases the period and wavelength decrease

38
Q

If period and wavelength increase what happens to frequency?

A

The frequency will decrease

39
Q

What is propagation speed ?

A

Propagation speed (c) is the speed in which a wave moves through a medium

40
Q

What is the average speed of sound through soft tissue?

A

1.54 mm/us

1540 m/s

41
Q

What determines propagation speed?

A

The medium in which it travels through

42
Q

What ways can strength of a wave be described?

A

Amplitude
Intensity
Power

43
Q

What is amplitude?

A

The maximum displacement of an acoustic variable
Strength of wave determined by source of sound
(From middle of wave to crest or trough)

44
Q

What is intensity?

A

A way to define the strength of a wave

Is concentration of energy in a sound beam

45
Q

How is intensity and amplitude related? And what does it mean?

A

(I) is proportional to (Amp)squared

A SMALL change in amplitude results in LARGE change in intensity

46
Q

How is intensity related to power and area?

A

I = (P/A)

47
Q

What does the relationship between intensity,power and area show?

A

Shows that as area increases, intensity decreases

Like a flashlight beam moved closer and further away from a surface

48
Q

Intensity is not uniform in —— or ——, and we refer to intensities as these

A

Space and time

49
Q

Describe space intensity

A

In sound beam the intensity is the greatest at the centre and fades towards outside. NOT UNIFORM

50
Q

Describe time intensity.

A

Sound from the machines is sent in pulses (NO intensity during listening phase)
Within a pulse the intensity starts off high at beginning and falls off

51
Q

Space and time must be considered for——

A

Dose (how much energy is sent into patient)

Terminology used to assess bioeffects

52
Q

The greatest intensity found across the beam is called the —— and is usually found at the centre.

A

Spatial peak (SP)

53
Q

The average intensity measured over the entire beam is what ?

A

Spatial average (SA)

54
Q

SP and SA are related by what?

A

Beam uniformity ratio (BUR)

55
Q

What is the equation that relates the BUR, SP and SA

A

BUR = (SP / SA)

56
Q

What is temporal peak? (TP)

A

The greatest intensity found in the pulse

57
Q

The average for all values found in a pulse is called?

A

Pulse average (PA)

58
Q

Can TP and PA be used interchangeably?

A

Yes they can, they are almost identical

59
Q

This includes the dead time between pulses (listening phase), when there is no intensity.

A

Temporal average (TA)

60
Q

TP and TA are related by what ?

A

Duty factor (DF)

61
Q

What is the equation that relates TA, TP and DF

A

TA
DF = ——
TP

62
Q

What is the highest intensity about sound beam

A

SPTP

Not realistic it happens too quick to be able to use it for anything

63
Q

What intensity do we use for biological considerations.

A

SPTA

Highest intensity average over total experts expect time

64
Q

What is lowest intensity about sound beam

A

SATA

65
Q

To convert possible intensities from one to another use?

A

SP TA
BUR = —— DF = ——
SA TP

66
Q

Consider SPTA the list the different modes of ultrasound from lowest to highest values.

A 
Lowest
M mode
Real time-B mode 
Doppler
Continuous wave (no dead time SPTP) 
           Highest
67
Q

SPTA values are dependent on ?

A

Depth (go deeper it changes shape of beam)

68
Q

Velocities differ in different tissues, and this may result in —— appearing on the monitor

A

Artifacts

69
Q

Propagation speed in fat

A

1460 m/s

70
Q

Propagation speed in bone

A

4080 m/s

71
Q

Does frequency change speed?

A

NO

72
Q

What is the range equation used to calculate?

A

Used to calculate the distance of a reflector from the probe

73
Q

What is the range equation ?

A

D = C times t

D is distance there and back
C is the average speed of sound
t is time there and back

74
Q

What is the 1 cm rule

A

Another way to calculate the distance from the probe to the reflector (interface)

Takes 13us to travel 1 cm there AND back

75
Q

Can electromagnetic waves travel through space

A

Yes

76
Q

What control on ultrasound machine can be adjusted to change the wavelength of the emitted sound?

A

You can adjust the frequency which will change the wavelength

77
Q

What is the propagation speed for sound through air?

A

330 m/s

78
Q

Out of 3 MHz, 5MHz, and 7MHz which has the best resolution? The best depth penetration?

A

3MHz for the best depth

7MHz for the best resolution

Ambers Physics 1 (7 decks)

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