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Vascular II & Physics II > Physics Final Ch. 13-24 > Flashcards

Physics Final Ch. 13-24 Flashcards

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1
Q

Accuracy in time. Describes the ability to accurately show structures from instant to instant

A

temporal resolution

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2
Q

Temporal resolution is determined by

A

frame rate

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3
Q

System settings that affect frame rate

A

imaging depth, number of pulses per scan

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4
Q

Multiple focal zones ______ the frame rate and _______ temporal resolution but has improved ______

A

decrease, diminishes, lateral resolution

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5
Q

More pulses per scan line creates multiple focal zones

A

multi focus

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6
Q

Allows the sonographer to control whether the low-level gray scale information within the data will appear on the displayed image

A

Reject

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7
Q

Another name for reject

A

threshold or suppression

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8
Q

Reject effect on the image

A

affects all low level signals on the image, regardless of their location

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9
Q

Reject does not affect

A

bright echoes

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10
Q

Made up of a single PZT element in the transducer, the electronics in the beam former/pulser, and the wire that connects them

A

channel

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11
Q

6 major components of an ultrasound system

A

transducer, pulser/beam former, receiver, display, master synchronizer

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12
Q

During transmission, transforms electrical energy into acoustic energy and during reception, transforms acoustic energy into electrical energy

A

transducer

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13
Q

Creates and controls the electrical signal sent to the transducer that generates sound pulses

A

pulser/beam former

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14
Q

The pulser determines the

A

amplitude, PRP, PRF

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15
Q

The beam former determines the

A

firing delay patterns for phased array systems

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16
Q

Transforms the electrical signals from the transducer (produced by the reflected sound) into an image to display

A

receiver

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17
Q

Presents processed data-screen

A

display

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18
Q

Archival of data

A

storage

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19
Q

Maintains and organizes the systems components

A

master synchronizer

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20
Q

Spatial resolution is also called

A

detailed resolution

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21
Q

Spatial resolution is determined by

A

pixel density

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22
Q

How to calculate number of gray shades

A

multiply 2 by itself the same number of times as there are bits

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23
Q

Determines the range of brilliancies within the displayed image

A

contrast

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24
Q

Bistable images are _____ contrast (black and white)

A

high

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25
Q

Gray scale is ______ contrast

A

low

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26
Q

Composed of two shades, black and white

A

bistable images

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27
Q

Gray scale displays _____ levels of brightness

A

multiple

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28
Q

Many shades of gray have better

A

contrast resolution

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29
Q

With sector shaped images, the scan lines separate at increasing depths. “Gaps” or “missing information” exists between the scan lines, especially as the lines spread apart

A

fill-in interpolation

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30
Q

Fill-in interpolation is form of

A

preprocessing

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31
Q

Fill-in interpolation improves

A

spatial resolution

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32
Q

Creation of an image from sound reflections at twice the frequency of the transmitted sound

A

harmonic imaging

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33
Q

Harmonic frequency sound waves arise from _______ behavior

A

non-linear

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34
Q

As sound waves travel in the bod, a miniscule amount of energy is converted from the fundamental frequency to the harmonic frequency

A

tissue harmonics

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35
Q

Tissue harmonics occurs during

A

transmission

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36
Q

Tissue harmonics are

A

non-linear

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37
Q

Series of compressions and rarefactions

A

sound

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38
Q

Sound travels at an _______ speed through soft tissue

A

uneven

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39
Q

Sound is ______ through compression and ______ through rarefaction

A

faster, slower

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40
Q

As an ultrasound pulse interacts with contrast agents, _______ harmonics are generated

A

much stronger

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41
Q

Contrast harmonics are created because the microbubbles act in a _____ manner when struck by sound waves

A

non-linear

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42
Q

Contrast harmonics are created during

A

reflection

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43
Q

Occurs when blood moves with variable velocity

A

pulsatile

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44
Q

In pulsatile flow, blood accelerates and decelerates as a result of

A

cardiac contraction

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45
Q

Pulsatile flow commonly appears in

A

arterial circulation

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46
Q

Occurs when blood moves at variable velocity

A

phasic

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47
Q

In phasic flow, blood accelerates and decelerates as a result of

A

respiration

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48
Q

Phasic flow commonly appears in

A

venous circulation

49
Q

Occurs when a fluid moves at a constant speed or velocity

A

steady

50
Q

Steady is present in

A

venous circulation with held inspiration/expiration

51
Q

Characterized by chaotic flow patterns in many different directions and at many velocities

A

turbulent flow

52
Q

Sound associated with turbulence is called a

A

murmur or bruit

53
Q

A narrowing in the lumen of a vessel

A

stenosis

54
Q

Effects stenosis has on blood flow

A

changes in direction, increase in velocity, post stenotic turbulence, pressure gradient

55
Q

Velocity is highest where the vessel is

A

narrowest

56
Q

The streamlines are destroyed and turbulence in the form of

A

eddy currents/vortices

57
Q

Tissue vibration is called a

A

thrill

58
Q

Pressure downstream from the stenosis is _____ than the pressure upstream

A

lower

59
Q

Describes the relationship between velocity and pressure in a moving fluid

A

bernoulli’s principle

60
Q

Pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level

A

hydrostatic pressure

61
Q

If blood pressure measurement is made at the level of the heart, the hydrostatic pressure is ______, no error in measured pressure

A

0mmHg

62
Q

If the blood pressure measurement is made below the level of the heart, the measured blood pressure is

A

erroneously high

63
Q

If the blood pressure measurement is made above the level of the heart, the measured blood pressure is

A

erroneously low

64
Q

Change in frequency from motion between the sound source and the receiver

A

doppler shift/doppler frequency

65
Q

The frequency of sound changes when the sound source and the receiver move

A

closer together or farther apart

66
Q

Doppler shift is a principle used to measure the

A

velocity of blood in the circulation

67
Q

Doppler Shift (Hz)=

A

reflected frequency-transmitted frequency

68
Q

Doppler shifts are in the ______ range of frequencies

A

audible

69
Q

Doppler shifts are created when transmitted sound wave strikes

A

moving red blood cells

70
Q

Blood flow is moving toward the transducer

A

positive doppler shift

71
Q

Blood flow is moving away from the transducer

A

negative doppler shift

72
Q

Simultaneous anatomic imaging and doppler is called

A

duplex imaging

73
Q

Advantage of PW doppler

A

being able to select the exact location where velocities are measured

74
Q

PW doppler exact location is called

A

range resolution, range specicity, range specific

75
Q

Most common error associated with doppler ultrasound

A

aliasing

76
Q

An alias is a

A

false identity

77
Q

The false identity in PW doppler is that very high velocities in one direction are

A

incorrectly displayed as going in the opposite direction

78
Q

Does aliasing happen with CW doppler

A

no

79
Q

Aliasing occurs when the doppler sampling rate (PRF) is

A

too low in comparison to the measured blood velocities

80
Q

Two ways to avoid aliasing

A

raise PRF (nyquist limit), reduce doppler shift

81
Q

Color doppler reports/measures

A

average or mean velocities

82
Q

Color doppler is angle

A

dependent

83
Q

If the angle between the sound beam and blood flow is 90 degrees

A

no doppler shift is created or measured, no color will appear in the vessel

84
Q

To correct aliasing on color doppler is to

A

increase scale/PRF/nyquist limit

85
Q

Increasing the color doppler scale

A

decreases the sensitivity to low velocity flow

86
Q

Identifies only the presence of a doppler shift

A

power doppler

87
Q

Power doppler does not evaluate

A

velocity or direction

88
Q

Power doppler mode is

A

non-directional color doppler

89
Q

Advantages of power doppler mode

A

increases sensitivity to low flow/low velocity flow, unaffected by doppler angles, no aliasing

90
Q

Disadvantages/limitations of power doppler mode

A

no velocity or flow direction, low frame rate

91
Q

Appears as a hyperechoic region beneath tissue with abnormally LOW attenuation

A

enhancement

92
Q

Enhancement is completely unrelated to

A

speed of sound in soft tissue

93
Q

What assumption is not true with enhancement

A

6 the strength of a reflection is related to the characteristics of the tissue creating the reflection

94
Q

Appears when the sound energy is transmitted in a direction other than along the beams main axis

A

lobes

95
Q

Lobe artifacts degrade

A

lateral resolution

96
Q

What assumption is not true with lobes

A

4 reflections arise from structures located along the beams main axis

97
Q

Lobe artifact and true reflector are located ______ and ______

A

side by side, at the same depth

98
Q

Created when sound reflects off a strong reflector and is redirected toward a second structure

A

mirror image

99
Q

Mirror artifact is located

A

deeper than the real structure

100
Q

Slice thickness artifact is related to dimension of the beam that is

A

perpendicular to the imaging plane

101
Q

Small amplitude echoes and results from many sources

A

noise

102
Q

Noise is more likely to affect ______ regions rather than ______

A

low level hypoechoic regions, bright echogenic areas

103
Q

Phantoms are an

A

objective standard

104
Q

Have ultrasonic features similar to soft tissue, used to evaluate gray scale, tissue texture, multi focus

A

tissue equivalent phantom

105
Q

Tissue equivalent phantom is similar to soft tissue in what 4 ways

A

speed of sound in phantom is 1540 m/sec, attenuation, scattering characteristics, echogenicity

106
Q

Region close to the transducer where images are inaccurate

A

dead zone

107
Q

In dead zone, it extends from the transducer to

A

shallowest depth where reflection appears

108
Q

Dead zone is assessed with the

A

shallowest pins in a test phantom

109
Q

What can be used for help with dead zone for superficial structures

A

acoustic standoff (or gel pad)

110
Q

Minimum distance at which two side by side pinds are displayed as two distinct images, PERPENDICULAR TO SOUND BEAM

A

lateral resolution

111
Q

Smallest distance at which two pins positioned PARALLEL to the sound beam are displayed as two distinct echos

A

axial resolution

112
Q

Quality of being worthy, honored or esteemed

A

dignity

113
Q

Factors that make a patient vulnerable to a loss of dignity include

A

advanced age, infirmity, lack of privacy

114
Q

A primary mandate regarding clinical ultrasound is that the

A

benefit to the patient must outweigh the risk of the exam

115
Q

Maximal heating is related to the beams

A

SPTA intensity

116
Q

Interaction of sound waves with microscopic, stabalized, gas bubbles (gaseous nuclei) in the tissues

A

cavitation

117
Q

Proposed that bioeffects result from tissue temperature elevation

A

thermal mechanism

118
Q

It is ______ to use diagnostic ultrasound in a non-medical setting for entertainment

A

inappropriate

Vascular II & Physics II (21 decks)

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