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DMSO Physics 2 > SPI review 2 > Flashcards

SPI review 2 Flashcards

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1
Q

attenuation coefficient and its units

A

the amount of attenuation per cm units dB/cm

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2
Q

attenuation cefficient is directly related to

A

frequency

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3
Q

attenuation coeff does not change when ________ changes

A

path length

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4
Q

in soft tissue attenuation coeff is approcimatley

A

1/2 the freqyency

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5
Q

mathmatical expression for attenuation coeff in soft tissue

A

0.5dB/cm/MHz

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6
Q

impedance

A

a number associated with a meduims resistance

calculated not measured

units are Rayls “Z”

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7
Q

acoustic impedance =

A

density x propagation speed

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8
Q

rayleigh scattering is =

A

freq to the 4th

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9
Q

oblique incidence

A

anything other than right angels

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10
Q

AKA normal incidence

A

perpendicular
orthogonal
right angel
ninety degrees

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11
Q

typical % of reflected intensity between soft tissue boundary

A

1%

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12
Q

% refelcted at air/tissue interface

A

99%

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13
Q

% reflected at bone/tissue interface

A

50%

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14
Q

refraction is

A

transmission with a bend

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15
Q

the physics of refraction is described by

A

snells law

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16
Q

refraction requirs _____ incidence

A

oblique (and diff speeds)

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17
Q

the angel of reflections is = to

A

the angle of incidence

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18
Q

which of the following best descrobes a refelction from a rough boundry?
non diffuse, absolute, rayleigh, smooth, non specular

A

non specular

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19
Q

the time of flight and and distance are ________ related

A

directly

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20
Q

range equation

A

distance to boundry = go return time x speed / 2

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21
Q

in soft tissue, every ____ of go return time means the reflector is ___ deeper in the body

A

13 micro sec

1cm

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22
Q

a property of certain material to create a voltage when pressure is applied or when the material is mechanically deformed

A

piezoelectric effect

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23
Q

materials deform or change shape when a voltage is applied to them

A

reverse piezoelectric effect

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24
Q

PZT AKA

A

ferroeclectric material

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25
Q

natural PZT

A

quartz, rochelle salts, tourmaline

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26
Q

man made PZT

A

barium titanate, lead metaniobate, lead titanate, lead zirconate titanate

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27
Q

temp PZT will depolarize at

A

360C* or 680F*

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28
Q

the complete destruction of all living microorganisms by heat, chemical agents, or radiation

A

sterilization

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29
Q

reduce infectious organisms

A

disinfection

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30
Q

thickness of PZT

A

1/2 wavelength thick

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31
Q

thickness of matching layer

A

1/4 wavelength thick

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32
Q

what is backing material made of

A

epoxy resin impregnated with tungsten

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33
Q

imaging transducer characteristics

A

damping

short pulse length and duration

low sensitivity

wide bankwidth

low Q factor

decreased output power

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34
Q

bandwidth

A

the range of frequencys from the highest to the lowest emitted from the transducer

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35
Q

bandwidth =

A

max freq - min freq

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36
Q

the process of _______ increases the range of freq in the bankwidth

A

backing material

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37
Q

main freq AKA

A

center

resonant

primary

natural freq

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38
Q

a unitless number representing the extent of damping

A

quality factor (Q factor)

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39
Q

the Q factor in typical imaging can be aprroximated by the number of _____ __ _______

A

cycles in the pulse

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40
Q

typical Q factor value

A

2-4

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41
Q

Q factor equation

A

Q = resonant freq/bandwidth

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42
Q

in pulsed wave transducers the main or center freq of the US pulsed transducer is determined by 2 characteristics of the crystal

A

thichness and prop speed

43
Q

prop speed for PZT is approx

A

4-6mm/micro sec

44
Q

in continouis wave trans the sound waves freq = the _______

A

freq of the voltage applied to the PZT by the machines electronics

45
Q

when the PZT is 1/2 as thick the sounds freq is ____ __ _____

A

twice as high

46
Q

the thinner the active element the _____ the freq

A

higher

47
Q

the _________ the active materials prop speed the ________ the transducers freq

A

faster

higher

48
Q

thin crystal and fast PZT =

A

higher freq

49
Q

thick crystal and slow PZT =

A

lower freq

50
Q

when a transducer is covered with gel on the inside, what can’t it come into contact with in order to make the image? gel, water, talcum powder, sterile liquid, lubricating gel

A

talcum powder

51
Q

t or f
if the freq of the electrical excitation voltage of a pulsed wave transducer is 6MHz, the main or ceter freq of the transducer is 6MHz

A

F

52
Q

the impedance of a transducers active element is 1,900,000Z and for the skin is 1,400,000Z what is an acceptable impedance for the matching layer? 1,200,000Z, 1,400,000Z, 1,726,000Z, 1,950,000Z

A

1,726,000Z

53
Q

T or F

the damping material improves the systems longitudinal res

A

T

54
Q

narrow beams create ______ images

A

better

55
Q

for unfocused continuous wave disc transducers, at the end of the near zone the beam diameter is __ the ________ _______

A

1/2

transducer diameter

56
Q

at 2 near zone lengths, the beam diameter is ____ to the _______ -________

A

=

transducer diameter

57
Q

two factors that determine focal depth (distance from tranducer to the focal point)

A

transducer diameter

freq of ultrasound

58
Q

beams with a deep focas have a _____ ______ at the focus

A

lower intensity

59
Q

shallow focus

A

small diameter

low freq

60
Q

deep focus

A

large diameter

high freq

61
Q

divergence is determinded by

A

transducer diameter

freq of ultrasound

62
Q

in the far field, beam is narrow ________ res is the best with large diameter and high freq

A

lateral

63
Q

in the far field, beam is wide where _______ res is worse, with small diameter and low freq

A

lateral

64
Q

less divergence

A

narrower beam in far field

larger diameter active element

high freq

improved lateral res in far field

65
Q

more divergence

A

wider beam in far field

small diameter active element

low freq

degraded lateral res in far field

66
Q

v shaped wave

A

diffraction pattern
aka
huygens wavelet

67
Q

huygens wavelet caused by

A

produced by a tiny source near the size of a wavelength, the waves will diverge in hour glass or V shage as they propagate

68
Q

what happens in a huygens wavelet

A

each tiny part of transducer is individual source of sound. V shape is result of constructive and destructive interference of the many sound wavelets emitted from numerous soud sources.

69
Q

a sound beam is created by a round PZT with a diameter of 10mm. The focal depth of the sound beam is 8cm. What is the diamter of the sound beam at a depth of 8cm? 8cm, 3mm, 5mm, 4mm

A

5mm

70
Q

a sound beam is created by round pzt with a diameter of 10mm. The focal depth of the sound beam is 8cm. What is the diameter of the sound beam at a depth of 16cm? same as the trans diameter, 3/4 the trans diameter, 1/2 the transducer diameter, 4mm

A

the same as the transducer diameter

71
Q

the ability to image accurately, not merely quality

A

resolution

72
Q

the ability to distinguish two structures that are close to each other, front to back, paralley to, or along the beams main axis

A

axial resolution

73
Q

axial res AKA

A

L longitudinal
A axial
R range, radial
D depth

74
Q

units for axial res

A

distance

75
Q

shorter pulses create ______ LARD res

A

shorter

76
Q

can sonographer change LARD res

A

no, need new trans

77
Q

T or F

a short pulse means a short spatial pulse length or a short pulse duation

A

T

78
Q

when the LARD res is low the image accuracy is ________

A

superior

79
Q

LARD equation

A

LARRD = spatial pulse length/2

80
Q

typical LARRD value

A

0.05-0.5mm

81
Q

LARRD soft tissue Equation

A

LARRD=0.77x # cycles in pulse/freq

82
Q

LARRD is best with

A

less ringing (fewer cycles in pulse)

higher freq (shorter wavelength)

83
Q

the minimum distance that 2 structures are separated by side to side, perpendicular to the sound beam that produces 2 distinct echoes

A

lateral res

84
Q

lateral res AKA

A

L Lateral
A Angular
T Transverse
A Azimuthal

85
Q

units of LATA

A

length

86
Q

lateral res is = to

A

the beam diameter

87
Q

since the beam diameter varies with _____ LARA res also vaies with _____

A

depth

88
Q

lata res is best at

A

the focus or one near zone length (focal depth from the transducer because the sound beam is narrowest at that point

89
Q

when 2 side by side structures are closer together than the beams width

A

only one wide reflection is seen on the image

90
Q

why is LATA not as good as LARRD

A

US pulses are wider than they are short

91
Q

LATA res is = to

A

beam diameter

92
Q

high freq sound improves

A

LARRD everywhere in the image and LATA in the far field only

93
Q

focusing alters beam in what ways

A

narrower waist in the US beam

shallower focus

smaller focal zone

94
Q

focusing is effective in

A

the near field and focal zone

95
Q

two types of focusing

A

fixed aka conventional or mechanical

adjustable by electronics aka phases array

96
Q

phases array meand

A

adjustable or multi focusing

97
Q

3 methods of focusing

A

lens
curved pzt
electronic focusing

98
Q

lens

A

external focusing, distal to pzt

99
Q

curved pzt

A

internal focusing

100
Q

electronic focusing

A

adjustable, phased array

multy focusing

101
Q

fixed focus have _____ lateral res

A

poor

102
Q

an operation that lateral res of a given depth be estimated

A

measure the largest dimension on the image size of a point reflector

103
Q

the more cycles there are in a pulse, the ______ is the numerical value of range res

A

greater

DMSO Physics 2 (26 decks)

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