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DMS > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Importance of Physics

A
  • Learn DMS
  • Understand Artifacts
  • Prep for instrument performance measurements
  • Become aware of safety and risk factors
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2
Q

Doppler Effect

A

Christian Doppler

1840

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3
Q

Piezoelectric Effect

A

Piere and Marie Curie

1880

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4
Q

Distance Formula

A

Distance = Rate of speed X time of trace

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5
Q

Rate of speed in soft tissue?

A

1540 m/s
Or
1.54 mm/us

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6
Q

13 microsecond rule

A

Time for sound to travel 1cm and back in soft tissue

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7
Q

Linear Scan

A
  • Rectangular Display

- Pulses travel in the same direction

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8
Q

Sector Scan

A
  • each pulse shares origin

- subsequent pulses go out in different directions

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9
Q

Doppler Effect -> in ultrasound

A

If an echo generating structure is moving, the echo will have a different frequency than pulse enjoyed by the transducer

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10
Q

Metric Measurements

Mega(M)

A

Million (10^9)

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11
Q

Metric Measurements

Kilo(k)

A

Thousand(10^3)

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12
Q

Metric Measurements

Hecto(h)

A

Hundred (10^2)

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13
Q

Metric Measurements

Centi(c)

A

Hundredth(10^-2)

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14
Q

Metric Measurements

Mili(m)

A

Thousandth(10^-3)

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15
Q

Metric Measurements

Micro(u)

A

Millionth(10^-6)

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16
Q 
Metric Measurements
M
k
h
c
m
m(u)
A

Mortal kombat has crazy many murders(u)

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17
Q

Sound

A

The sensation produced by vibrations through a medium; gas, liquid, etc

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18
Q

Wave

A

A disturbance that travels through a medium and moves its energy from one location to another

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19
Q

Compression

A

An area of increased particle density

Top of wave

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20
Q

Refraction

A

An area of decreased particle density

Bottom of wave

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21
Q

Acoustic Variables

A

Pressure
Density
Particle Motion (Disturbance)
Temp

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22
Q

Acoustic Variables

Pressure

A

Concentration of force

Units: Pascals (Pa), lbs/sq in, atmospheres

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23
Q

Acoustic Variables

Density

A

Concentration of mass or weight

Units: kilo per cubic cm

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24
Q

Acoustic Variables

Particle Motion

A

Distance

Units: meter, cm, feet

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25
Q

Acoustic Variables

Temp

A

Measurement of heat

Units: Degrees

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26
Q

Ultrasound Pulse Principles

A
  • Pulse Repetition Frequency
  • Pulse Repetition Period
  • Pulse Duration
  • Duty Factor
  • Spatial Pulse Length
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27
Q

Range Equation

A

Distance = Rate x Time

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28
Q

What is a Pulse?

A
  • a short burst of sound energy
  • a collection of a number of cycles
  • all these cycles travel together
  • each Pulse has a beginning, middle, & end
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29
Q

PRF

A

Pulse Repetition Frequency

  • number of pulses the ultrasound transducer emits in 1 second of time
  • units: Hz or kHz
  • typical range of PRF is 1-10 kHz
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30
Q

PRP

A

Pulse Repetition Period

  • the time from the beginning of one pulse to the start of the next Pulse
  • PRP includes the time the machine is producing the pulse and the time it is listening for the pulse to return
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31
Q

What is the relationship between PRP & PRF?

A

They are reciprocals
Ex)
-PRF=(1/PRP)
-PRP=(1/PRF)

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32
Q

Can PRP be changed?

A

Yes, because PRF is the reciprocal of PRR and PRP can be adjusted on the US machine

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33
Q

PD

A

Pulse Duration

  • the time (duration) of an ultrasound pulse
  • units: time (microseconds)
  • typical PD for US is 0.5-0.3 microseconds
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34
Q

PD equation

A

Pulse Duration = # of cycles in a pulse x period

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35
Q

PD increases if?

A
  • Period increases
  • # of cycles in pulse increases
  • frequency decreases
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36
Q

DF

A

Duty factor

  • the fraction of time that the ultrasound machine is sending out a pulse of sound
  • DF is expressed as a decimal point or fraction
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37
Q

DF equation

A

Duty factor = Pulse Duration / Pulse Repetition period

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38
Q

Acoustic Variables

A

Pressure
Density
Particle vibrations/movements
Temperature

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39
Q

Bigness Parameters

A

Amplitude
Power
Intensity
Attenuation

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40
Q

Amplitude

A

The maximum variation in an acoustic variable

41
Q

Decibels

A
  • not an exact number
  • used to express a ratio or difference between a reflected signal and source signal
  • based info logarithmic scale of numbers
42
Q

Positive decibels

A 
\+3dB = doubling intensity (2x the original)]
\+6dB = quadrupling intensity (4x the original)
\+9dB = 8x the original
\+10dB= 10x the original
\+20dB = 100x the original
43
Q

Negative decibels

A
  • 3dB = halfing intensity (½ the original)
  • 6dB = quartering intensity (¼ the original)
  • 9dB = ⅛ the original
  • 10dB = 1/10 the original
  • 20dB = 1/100 the original
44
Q

Logarithm (log)

A

-a mathematical numerical rating system
-the number of 10s that are multiplied together to equal a number
Ex) Log of 100 = 2

45
Q

How can a sonography change the amplitude?

A

Adjusting the Power Control

46
Q

Power

A

-rate of energy transference

47
Q

The number of pulses emitted in 1 second is termed what?

A

Pulse Repetition Frequency

48
Q

The beginning of one pulse to the beginning of the following pulse is termed pulse is termed what?

A

Pulse Repetition Period

49
Q

What is the relationship between PRF and PRP?

A

They are reciprocals

50
Q

When we increase depth what happens to the Pulse Repetition Period

A

PRP increases

51
Q

When we increase depth what happens to Pulse Repetition Frequency?

A

PRF Decreases

52
Q

What term measures the duration of the US pulse?

A

Pulse Duration

53
Q

What formula for Pulse Duration? What are the units?

A

PD= (# of cycles in pulse) x (period)

54
Q

What term do we use for the fraction of time the US machine is sending out a pulse?

A

Duty Factor

55
Q

What is the equation for the above term? What are the units?

A 
DF = PD / PRP
DF% = PD / PRP x 100
56
Q

What term do we use for the length of an US pulse?

A

Spatial Pulse Length

57
Q

What is the equation for SPL?

A

SPL = (# of cycles in pulse) x wavelength(mm)

58
Q

What are the units for PRP?

A

Seconds

59
Q

What are the units for PRF?

A

Hz of kHz

60
Q

What is the term when the US machine has just sent out a pulse and is waiting for it to come back?

A

Receiving time

61
Q

If Period decreases, what happens to the Pulse Duration?

A

PD decreases

62
Q

What happens to SPL if Frequency increaseS?

A

SPL Decreases

63
Q

Three components of attenuation?

A

Reflection
Absorption
Scatter

64
Q

As path length increases, the attenuation of ultrasound in soft tissue?

A

Path length increases = path length increases

65
Q

Units of attenuation?

A

dB/cm

66
Q

T/F

In a given medium, the attenuation is unrelated to the speed of sound

A

True

67
Q

What are the units of half layer thickness?

A

Cm & mm

68
Q

As Frequency decreases, what happens to the depth of penetration?

A

It increases

69
Q

T/F Amplitude, power and intensity can be changed by the sonographer?

A

True

70
Q

Which intensity is related to tissue heating?

A

SPTA

71
Q

What is the importance of describing sound beam intensities in a variety of ways with regard to space and time?

A

Intensity is important in bio effects

72
Q

What are the units of the transmitted intensity of a sound wave?

A

Watts/cm^2

73
Q

As the sound travels in the body, what happens to the intensity of the wave?

A

Intensity decreases

74
Q

What determines the initial amplitude if a wave?

A

The transducers capability determines the initial amplitude

75
Q

Requirements for refraction

A
  • oblique incidence

- different propagation speeds between the media

76
Q

Refraction

A

Bending of a beam of sound, or change in direction of a beam of sound as it passes from one medium to another

77
Q

Oblique incidence

A

Anything besides 90 degree incidence

  • reflection uncertain
  • transmission uncertain
78
Q

Relation of incidence angle and reflection angle “Law of Reflection”

A

Incidence angle = reflection angle

40 degree = 40 degree

79
Q

Average impedance for soft tissue

A

1,630,000 Rayls
Or
1.63 x 10^6

80
Q

2 factors for reflection to occur

A

1) angle @ which sound strikes the boundary must be 90 degrees
2) the 2 tissues or mediums must have different acoustic impedances

81
Q

IRC & ITC relationship

A
  • IRC & ITC must = 100% of original intensity
  • all sound must be accounted for

Ex: if IRC is 3% then ITC should be 97%

82
Q

Reflected sound

A

The sound that is reflected @ the boundary or interface & returns to the transducer

83
Q

Transmitted sound

Transmission

A

The sound that continues to propagate I. The direction it was going, after hitting a boundary of interface

84
Q

Incident sound

A

The sound that is coming from the sound source & going to the medium

85
Q

How is Rayleigh scattering affected by Frequency?

A

Frequency increases, scattering increases

86
Q

Scattering

A
  • occurs when sound encounters irregular, boundaries or tissue
  • redirected into many directions
87
Q

2 types of scattering

A

Backscatter (diffused reflection): sound returns toward the transducer

Rayleigh scattering : sound is redirected in all directions

88
Q

dB in relation to increasing or decreasing power or gain

A

+dB = increases in value (turn up power or gain)

-dB = decrease in value (turn down power or gain

89
Q

Relationship between Period & Frequency (PRP & PRF)

A

Reciprocals (inversely related)

-PRF = 1/PRP or PRP = 1/PRF

90
Q

Sound speed in different tissues

A

Solids are faster than liquids, liquids are faster than gases

91
Q

Density of medium

A

Density increase = speed of sound decrease

Density decrease = speed of sound increase

92
Q

Hardness of medium

A
  • Dominant role
  • the stiffer or less elastic a medium is the faster the sound travels in it
  • stiffness increase then the speed increases
  • stiffness decreases then the speed of sound decreases
93
Q

2 properties of medium affecting speed of sound

A

1) hardness of medium (stiffness)

2) density of medium ( related to weight)

94
Q

What affects propagation speed

A
  • only the medium affects propagation speed

- if the medium does not change, the speed of sound will not change

95
Q

What affects wavelength?

A
  • transducer Frequency

- the medium sound travels in

96
Q

Wavelength

A
  • Reciprocal of frequency
  • length of space that one wave occupies
  • units: mm, meters, inches, etc
  • US units = mm
  • US wavelength = 0.1-0.8
97
Q

Ultrasound Frequencies

A

Usually between 2.0-12.0mHz
Choice of frequency affects:
1) penetration
2)image resolution - increased frequency

Frequency is determined by the transducer

98
Q

Categories of sound

A

Infrasound: <20Hz
Audible sound: within range of hearing 20Hz - 20,000Hz
Ultrasound: >20,000Hz

99
Q

Image depth equation

A

(Rate x Time) / 2

DMS (5 decks)

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