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Vascular I & Physics I > Ch. 8-9 Physics > Flashcards

Ch. 8-9 Physics Flashcards

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1
Q

Materials that convert electricity into sound and vice versa is called

A

piezoelectric or ferroelectric

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2
Q

The piezoelectric material we use in ultrasound is man made and is

A

lead zirconate titanate or PZT

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3
Q

PZT is also know as the

A

crystal, active element or ceramic

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4
Q

Other piezoelectric materials found in nature are

A

quartz and tourmaline

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5
Q

The temperature at which PZT is _____ is called the ______ or ______

A

polarized, curie temperature, curie point

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6
Q

Process of exposing the PZT to a strong electrical field while being heated to the curie temperature

A

polarization

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7
Q

If PZT is heated above the curie point, it becomes

A

depolarized

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8
Q

A transducer is any device that converts one form of ____ to another

A

energy

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9
Q

During _______, electric energy from the system is converted to sound

A

transmission

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10
Q

During ______, the reflected sound is converted into electricity

A

reception

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11
Q

Describes the property of certain materials to _____ a voltage when they are mechanically deformed or when pressure is applied to them

A

the piezoelectric effect, create

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12
Q

The piezoelectric material change shape when a voltage is applied to them

A

reverse piezoelectric effect

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13
Q

Protects the internal components- insulates the patient from electrical shock

A

case

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14
Q

thin metallic barrier lining the inside of the case- keeps electrical signal in the air from entering the transducer- prevents electrical noise from contaminating the images

A

electrical shield

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15
Q

Cork or rubber barrier- prevents the vibrations in the case

A

acoustic insulator

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16
Q

The piezoelectric crystal itself

A

PZT/active element

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17
Q

PZT is _____ wavelength thick

A

1/2

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18
Q

provides electrical connection between the PZT and the US system

A

wire

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19
Q

Positioned in front of the PZT- at the face of the transducer

A

matching layer

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20
Q

The matching layer is ____ wavelength thivk

A

1/4

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21
Q

Increases the efficiency of sound energy transfer between the active element and the body

A

matching layer

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22
Q

Protects the active element

A

matching layer

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23
Q

Bonded to the back of the active element

A

backing material/damping

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24
Q

Reduces the “ringing” of the crytsal

A

backing material/damping

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25
Q

Damping enhances

A

axial resolution

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26
Q

Damping also reduces ______ during reception, so _____ sound reflections are not detected- creating _____ sensitivity

A

vibration, low-level, decreased

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27
Q

_____ and ______ increase the efficiency of sound transfer between the crystal and the skin

A

matching layer, gel

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28
Q

in DECREASING order of impedance

A

PZT>matching later>gel>skin

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29
Q

range of frequencies in a pulse. Difference between the highest and lowest frequency

A

bandwidth

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30
Q

Imaging probes produce pulses that are identified as

A

wide bandwidth of broadband

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31
Q

Therapeutic and continuous wave doppler probes DO NOT USE _________ and produce ____________ and DO NOT CREATE images

A

backing material/damping, narrow bandwidth pulses

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32
Q

Is a UNITLESS number that is _______ related to bandwidth

A

Quality factor (Q-factor), inversely

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33
Q

WIDE bandwidth probes (imaging probes) have a _____ q-factor

A

low

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34
Q

Therapeutic and CW doppler probes have a _____ bandwidth and a ______ Q-factor

A

narrow, high

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35
Q

Math for Q-factor

A

main frequency divided by the bandwidth

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36
Q

Pulses with short duration and length

A

imaging transducer

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37
Q

Uses backing material to limit ringing

A

imaging transducer

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38
Q

Reduced sensitivity

A

imaging transducer

39
Q

Wide bandwidth/broadband

A

imaging transducer

40
Q

Low Q-factor

A

imaging transducer

41
Q

Improved axial resolution

A

imaging transducer

42
Q

Created continuous wave or pulses with long duration and length

A

non-imaging transducer

43
Q

No backing material

A

non-imaging transducer

44
Q

Increased sensitivity

A

non-imaging transducer

45
Q

Narrow bandwidth

A

non-imaging transducer

46
Q

High Q-factor

A

non-imaging transducer

47
Q

Cannot create an image

A

non-imaging transducer

48
Q

Destruction of all microorganisms by exposure to extreme heat, chemical agents or radiation

A

sterilization

49
Q

Application of chemical agent to reduce or eliminate infectious organisms on an object

A

disinfection

50
Q

Continuous wave transducers frequency=

A

frequency of the electrical signal/voltage

51
Q

With pulsed wave transducers, two characteristics of the active element/crystal combine to determine the frequency of sound:

A

Speed of sound of the crystal, thickness of the crystal

52
Q

speed of sound in the crystal and frequency of sound are _____ related

A

directly

53
Q

Crystal thickness and frequency are ______ related

A

inversely

54
Q

Characteristics of high frequency pulsed wave transducers are

A

thin crystals with higher speed crystals

55
Q

Characteristics of low frequency pulsed wave transducers are

A

thick crystals with lower speed crystals

56
Q

Location where the US beam is the narrowest

A

focus/focal point

57
Q

The width of the sound beam at the focus is _____ the width of the beam as it leaves the transducer

A

1/2

58
Q

Region from the transducer to the focus

A

near zone/near field

59
Q

Near field/near zone is also called

A

fresnel zone

60
Q

The focus is located at the end of the

A

near zone

61
Q

Distance from the transducer to the focus

A

focal length

62
Q

Starts at the focus and extends deeper

A

far zone/far field

63
Q

Far zone/far field also called

A

fraunhofer zone

64
Q

In the far zone, the beam

A

diverges

65
Q

At the beginning of the far zone, the beam is _____ as wide as it is at the transducer (focus)

A

1/2

66
Q

When the beam is _____ near zone lengths from the transducer, the beam is again the same size as the active element- and then the beam diverges more

A

two

67
Q

Region around the focus where the beam is relatively narrow

A

focal zone

68
Q

______ arising from the focal zone created images that are more accurate then those from other _____

A

reflection, depths

69
Q

_____ of the focal zone is in the near field and _____ is in the far field

A

half, half

70
Q

How does transducer diameter affect the focal depth

A

Transducer diameter and focal depth are directly related

71
Q

So, with two transducers of different diameters, the transducer with the _____ diameter with have a DEEPER focus/DEEPER focal depth

A

larger

72
Q

How does frequency affect focal depth

A

frequency and focal depth are directly related

73
Q

So, two transducers with the same diameter but different ______ - the _____ frequency will have a deeper focus/deeper focal depth

A

frequencies, higher

74
Q

High frequency (which has shallower imaging depth) has a deeper focal depth is considered

A

clinical dilemma/ bad physics

75
Q

Low frequency (which allows for a deeper imaging) has a shallower focal depth is considered

A

clinical dilemma/ bad physics

76
Q

So, manufacturers make higher frequency transducer with extremely _________ crystals

A

small diameter

77
Q

So, manufacturers make lower frequency transducer with _________ crystals

A

larger diameter

78
Q

Describes the gradual spread of the US beam in the far field

A

sound beam divergence

79
Q

Two factors combine to determine beam divergence which are

A

transducer diameter and frequency of the sound

80
Q

How does the transducer diameter affect divergence in the far field

A

crystal diameter and beam divergence are inversely related

81
Q

Smaller diameter crystals produce beams thatspread out more in the

A

far field

82
Q

Large diameter crystals produce beams with ______ divergence

A

less

83
Q

Large diameter crystals improve _____ resolution in the ____ field

A

lateral, far

84
Q

How does frequency alter beam divergence in the far field

A

Frequency and beam divergence are inversely related

85
Q

Higher frequency transducers diverge ____ in the ____ field

A

less, far

86
Q

Lower frequency transducers diverge ____ in the ___ field

A

more, far

87
Q

So ____ frequency sound improves ____ resolution in the far field

A

high, lateral

88
Q

States that a large active element/crystal may be thought of as millions of tiny distinct sound sources

A

Huygens’ Principle

89
Q

Each of these tiny particles is a _____ source and creates a _____ wavelet with a ____-shape

A

Huygens’, Huygens’, V

90
Q

The V-shape waves are known as

A

spherical waves, diffraction patterns or Huygens wavelets

91
Q

The hourglass shape produced by a large crystal is the result of

A

interference of the many Huygens’ wavelets.

92
Q

Some wavelets are _______ (interfere constructively) and some of the wavelets are _______ (destructive interference)

A

in-phase, out-of-phase

93
Q

Explains the shape of an imaging transducer’s emitted sound beam based upon in-phase and out-of-phase wavelets interfering with each other

A

Huygens’ principle

Vascular I & Physics I (19 decks)

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