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US - Understanding US Physics > US - Understanding US Physics - 6 > Flashcards

US - Understanding US Physics - 6 Flashcards

1
Q

STR of attenuation r/t STR of amplitude

A

inverse

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2
Q

importance of increasing 1-log

A

by increasing 1-log&raquo_space; 10x more

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3
Q

DECIBEL NOTATION - absolute? measured? calculated?

A

.relative measurement

. comparison

.ratio

.logarithmic

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4
Q

DECIBELS require…

A

2 intensities… start & final

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5
Q

positive DECIBELS

A

final intensities is LARGER than start intensities

INCREASES in intensities

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6
Q

negative DECIBELS

A

final intensities is SMALLER than start intensities

DECREASES in intensities

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7
Q

+ 3dB

A

final intensity is DOUBLE start intensity

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8
Q

+ 10dB

A

final intensity is 10x TIMES start intensity

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9
Q
  • 3dB
A

final intensity is HALF (1/2) start intensity

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10
Q
  • 10dB
A

final intensity is ONE-TENTH (1/10) start intensity

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11
Q

ex: meaning of 6dB change?

A

** +3dB = 2x

6dB = 2 x (+3dB)
6dB = 2 x (2x)
6dB = 4x

final intensity is [[4x]] start intensity

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12
Q

ex: sound increases by a factor of 100?

want: decibel notation?

A

** 10x = +10dB

100 = 10 x 10
100 = 2 x (+10dB)
100 = [[[+20dB]]]

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13
Q

def ATTENUATION

A

= as sound propagates thru medium, sound pulse STR(Power, Amplitude, Intensity) decreases,

.SAME speed

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14
Q

ATTENUATION - 2 factors

A

. distance
. frequency of sound

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15
Q

ATTENUATION r/t its 2 factors

A

direct

up ATTENUATION
up DISTANCE
up FREQUENCY

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16
Q

ATTENUATION r/t decibels

A

ATTENUATION = negative decibels due to decreases in sound pulse STR

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17
Q

ATTENUATION - 3 processes

A

SAR-Attenuation

.scatter
.absorption
.reflection

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18
Q

def REFLECTION

A

= when sound waves strike a LARGE BOUNDARY, redirected back to the sound source

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19
Q

REFLECTION - 2 types

A

specular REFLECTION

diffuse REFLECTION

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20
Q

def SPECULAR REFLECTION

A

= 1 direction reflected
. smooth boundary

BAD - at off-axis or off angle = no reflection

GOOD - stronger STR reflection than diffuse reflection

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21
Q

def DIFFUSE REFLECTION

A

aka BACKSCATTER
=multi direction
=irregular surfaces

GOOD - suboptimal angle

BAD - weaker STR reflection than specular reflection

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22
Q

def SCATTERING

A

= SMALL boundary, sound waves RANDOMLY directed, in MULTI-direction

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23
Q

SCATTERING r/t frequency

A

direct

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24
Q

example of SCATTERING

A

lung tissues due to alveoli are filled with AIR

*AIR has HI-attenuation = HI-frequency&raquo_space; HI-scattering

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25
Q

def RAYLEIGH SCATTERING

A

= organized
=omnidirectional scattering (in all direction)

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26
Q

RAYLEIGH SCATTERING - example

A

red blood cells

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27
Q

RAYLEIGH SCATTERING equation r/t frequency

A

RAYLEIGH SCATTERING = frequency (^4) 4th power

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28
Q

REFLECTION - organized, back to transducer

A

specular REFLECTION

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29
Q

REFLECTION - organized, in all direction

A

rayleigh REFLECTION

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30
Q

REFLECTION - disorganized, back to transducer

A

diffuse / backscatter REFLECTION

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31
Q

REFLECTION - disorganized, in all directions

A

scattering REFLECTION

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32
Q

importance in US r/t attenuation, reflection & scattering

A

UP f
DOWN pulse
UP accuracy

UP attenuation
DOWN depth

therefore, to UP.accuracy & UP.depth&raquo_space; US goal, to UP.f as much as possible for HI.accuracy without compromising DEPTH

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33
Q

def ABSORPTION

A

= when US energy is converted into another energy form (heat)

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34
Q

ABSORPTION r/t frequency

A

direct

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35
Q

ABSORPTION r/t DEPTH, f, attenuation, pulse.L

A

up ABSORPTION
up frequency&raquo_space; up attenuation
down pulse.L

DOWN depth

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36
Q

ABSORPTION r/t UP.depth….f, attenuation, pulse.L

A

down ABSORPTION
down frequency&raquo_space; down attenuation
up pulse.L

UP depth

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37
Q

def ATTENUATION COEFFICIENT

A

= number of decibels of attenuation when sound travels 1cm

= dB/cm

*regardless of sound travel distance

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38
Q

ATTENUATION COEFFICIENT r/t sound travel distance

A

UNrelated

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39
Q

TOTAL ATTENUATION depends on (3)…

A

.sound frequency
.beam travel distance
.tissue type

40
Q

TOTAL ATTENUATION equation

A

TOTAL ATTENUATION (dB) = ATTENUATION COEFFICIENT (dB/cm) x distance (cm)

41
Q

ATTENUATION COEFFICIENT - soft tissue value

A

0.5 dB/cm/MHz

42
Q

ATTENUATION COEFFICIENT equation

A

ATTENUATION COEFFICIENT (dB/cm) = f (MHz) / 2

43
Q

ATTENUATION COEFFICIENT r/t frequency

44
Q

arrange ATTENUATION MEDIUM from hi»low

A

hi»low

AIR
BONE & LUNG
MUSCLE
SOFT TISSUE
FAT
FLUIDS, BLOOD, URINE
WATER

45
Q

ATTENUATION r/t AIR & its f

A

air ATTENUATION 100%

f > 1MHz

46
Q

ATTENUATION r/t LUNG, type reflection

A

LUNG ATTENUATION more than SOFT TISSUES

hi SCATTERING reflection due to air in lung tissue

47
Q

ATTENUATION r/t WATER, its f

A

water ATTENUATION less than SOFT TISSUES

hi HI f ~10MHz

48
Q

ATTENUATION r/t muscles

A

depends if sound travels along or across fibers

49
Q

def HALF-VALUE LAYER THICKNESS

A

aka PENETRATION DEPTH
aka HALF BOUNDARY LAYER

=distance sound travels in tissue that reduces half original intensity of sound

50
Q

HALF-VALUE LAYER THICKNESS - US range

A

0.25 - 1cm

51
Q

HALF-VALUE LAYER THICKNESS depends on (2)

A

medium

sound frequency

52
Q

thin HALF-VALUE LAYER THICKNESS & its medium (3)

A

HI f
HI attenuation

lung, bone, air

53
Q

thick HALF-VALUE LAYER THICKNESS & its medium (3)

A

LOW f
LOW attenuation

fat, fluid, water

54
Q

def IMPEDANCE

A

= acoustic impedance
= characteristic impedance

**CALCULATED!!!!!, not measured

55
Q

IMPEDANCE equation

A

IMPEDANCE (rayls, Z) = DENSITY (kg/m^3) x propagation speed (m/s)

56
Q

IMPEDANCE - range

A

1.25 - 1.75 Mrayls

57
Q

IMPEDANCE - determined by

58
Q

def INCIDENCE

A

the angle at which the waves strike the boundary determines the behavior of the pulse

59
Q

oblique angle

A

any angles NOT 90 degrees

60
Q

acute angle

A

LESS than 90 degrees

61
Q

right angle

A

90 degrees

62
Q

obtuse angle

A

MORE than 90 degrees

63
Q

def normal incidence

A

= the incident sound beam strikes the boundary at exactly 90 degrees

aka PORN
.Perpendicular
.Orthogonal
.Right angle
.Ninety degrees

64
Q

def oblique incidence

A

= when the incident sound beam strikes the boundary at angle NOT 90 degrees

65
Q

what occurs at the boundary between 2 media?

A

CONSERVATION OF ENERGY, 100%

66
Q

INCIDENT intensity equation

A

INCIDENT intensity (W/cm^2) = REFLECTED intensity + TRANSMITTED intensity

67
Q

def INTENSITY REFLECTION COEFFICIENT (IRC)

A

IRC = percentage of reflected intensity

68
Q

IRC value for soft tissue

A

equal, less than 1%

69
Q

IRC r/t soft-hard tissues

A

up IRC b/t SOFT-HARD tissues

70
Q

def INTENSITY TRANSMISSION COEFFICIENT (ITC)

A

= percentage of transmission intensity

71
Q

ITC value for soft tissues

A

equal, more than 99%

72
Q

ITC r/t soft-hard tissues

A

down ITC b/t SOFT-HARD tissues

73
Q

IRC & ITC equation r/t energy conservation

A

100% = IRC + ITC

74
Q

units INTENSITIES vs COEFFICIENT

A

intensity (W/cm^2)

coefficient (%)

75
Q

def REFLECTION w/ NORMAL incident

A

= when incident strikes at 90*

b/t media with DIFF IMPEDANCE

76
Q

what happens to REFLECTION w/ NORMAL incident with SAME IMPEDANCE?

A

SAME impedance

no REFLECTION w/ NORMAL incident

77
Q

REFLECTION w/ NORMAL incident r/t DIFF in IMPEDANCE

78
Q

INTENSITY REFLECTION COEFFICIENT equation

A

IRC (%) = [Z2 - Z1 / Z2 +Z1]^2 x {100}

79
Q

def INTENSITY TRANSMISSION COEFFICIENT (ITC)

A

= percentage intensity that continues to move forward at boundary b/t 3 media

80
Q

100% ITC

A

b/t 2 media with SAME IMPEDANCE

81
Q

INTENSITY TRANSMISSION COEFFICIENT (ITC) equation

A

INTENSITY TRANSMISSION COEFFICIENT (ITC) {%} = transmitted intensity (W/cm^2) / incident intensity (W/cm^2) X {100}

82
Q

INTENSITY TRANSMISSION COEFFICIENT (ITC) equation r/t energy conservation

A

ITC (%) = 1 - IRC (%)

100% = ITC + IRC

83
Q

def REFLECTION & TRANSMISSION w/ OBLIQUE INCIDENCE

A

its not YOU, it’s ME kinda COMPLICATION

84
Q

REFLECTION & TRANSMISSION w/ OBLIQUE INCIDENCE - 2 physical principles

A

. conservation of energy
. reflection angle = incident angle

85
Q

explain CONSERVATION OF ENERGY r/t OBLIQUE INCIDENCE -

A

100% = reflected coefficient + transmission coefficient

incident intensity (W/cm^2) = reflecte intensity + transmitted intensity

86
Q

explain REFLECTION ANGLE = INCIDENT ANGLE r/t OBLIQUE INCIDENCE

draw **note CH6

A

.in oblique incidence, the sound beam does not reflected directly back to the transducer

.with the IMAGINARY LINE locates PERPENDICULAR to the boundary, the INCIDENT angle = REFLECTED angle

87
Q

example of REFLECTION ANGLE = INCIDENT ANGLE r/t OBLIQUE INCIDENCE

A

car rear view mirror

88
Q

def REFRACTION

draw *note CH6

A

= transmission with a bend

= change in direction of wave propagation after it crosses the boundary

89
Q

REFRACTION - needs 2 conditions

A

. oblique incidence
. diff propagation speed b/t 2 media

90
Q

low REFRACTION r/t speed, b/t media

A

low REFRACTION

~similar speed

soft-fat
muscle-blood
soft-fluid

91
Q

hi REFRACTION r/t speed, b/t media

A

hi REFRACTION

DIFF speed

bone-soft

92
Q

SNELL’s LAW

A

=physics attempt to explain refraction

93
Q

SNELL’s LAW equation

A

sin{transmission angle} / sin{incident angle} = [propagation speed 2] / [propagation speed 1]

94
Q

def SINE

draw *note CH6

A

= angle adjacent to the side

95
Q

draw NO REFRACTION r/t angle and speed

A

NO refraction

same angle degree
same speed

96
Q

draw YES REFRACTION r/t angle and speed (large vs small)

A

YES refraction with LARGE diff
.incident < transmission angle
.speed 1 < speed 2

YES refraction. with SMALL diff
.incident > transmission angle
.speed 1 > speed 2

US - Understanding US Physics (5 decks)

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