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Fall 2014 study > CHART > Flashcards

CHART Flashcards

1
Q

Typical value of frequency

A

2-15MHz

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2
Q

Typical value of intensity

A

0.001-100 watts/cm^2

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3
Q

Typical value of propagation speed in soft tissue

A

1,540m/s

  1. 54Km/s
  2. 54mm/us
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4
Q

order of speed in media slow to fastes

A 
air              330
lung           300-1200
fat               1450
soft tissue  1540
tendon        1850
bone            2000-4000

air

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5
Q

Typical value of pulse duration

A

0.5-3us

made of 2-4 cycles

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6
Q

Shallow imaging

A

High PRF
High duty factor
Short PRP

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7
Q

Deep imaging

A

Low PRF
Low Duty factor
long PRP

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8
Q

3 Commandments of intensity

A
  1. Intensities may be reported in various ways with respect to space and time
  2. Intensity is the key parameter with regard to bioeffects. the different intensities are important in the study of bioeffects, SPTA is the most relevant with respect to tissue heating
  3. Peak is greater than average
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9
Q

Intensities highest to lowest

A 
SPTP
SATP
SPTA   most important for thermal bioeffects
SATA
SPPA
SAPA
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10
Q

attenuation is related to

A

frequency and path length

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11
Q

high frequency

long path length

A

more attenuation

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12
Q

low frequency

short path length

A

less attenuation

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13
Q

attenuation in media from greatest to least

A

air (greatest)
lung, bone
soft tissue
water(least)

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14
Q

refraction requires

A

Oblique incidence

different speeds

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15
Q

Imaging transducer characteristics

A 
backing material
short SPL
short pulse duration
low sensitivity 
wide bandwidth
low Q factor
decreased output power
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16
Q

What determines the resonant frequency for continuous wave transducer

A

electrical frequency equals sounds frequency

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17
Q

What determined the resonant frequency for pulsed wave transducer

A

thickness of the element

propagation speed of the element

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18
Q

thin crystal

fast PZT

A

higher frequency

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19
Q

Thick crystal

slow PZT

A

lower frequency

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20
Q

two factors that determine focal depth

A 
transducer diameter (aperture)
frequency
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21
Q

shallow focus

A

small diameter

low frequency

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22
Q

deep focus

A

large diameter

high frequency

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23
Q

beam divergence is determined by

A

aperture of ceramic

frequency

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24
Q

less divergence

A

narrower beam in the far field
large aperture
high frequency
improved lat res in the far field

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25
Q

More divergence

A

wider beam in the far field
small aperture
low frequency
degraded lat res in the far field

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26
Q

higher frequency sound

A

improves axial resolution in entire image

improves lateral resolution in the far field

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27
Q

how does focusing alter the beam

A
  1. narrower waist in the us beam
  2. shallower focus
  3. smaller focal zone
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28
Q

what are the two types of focusing

A

fixed and adjustable

mechanical, conventional and phased array

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29
Q

what are the three specific methods of focusing

A

1 lens (external)

  1. curved PZT (internal)
  2. electronic
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30
Q

image shape of mechanical transducer

A

sector

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31
Q

what type of transducers have mechanical steering

A

mechanical

annular

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32
Q

what type of transducers dont have any steering

A

switched (sequential)

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33
Q

what type of transducers have fixed focusing

A

mechanical
annular
linear sequential

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34
Q

Frame rate is determines by

A 
imaging depth
# of pulses per image
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35
Q

Frame rate is limited by

A

the speed of sound in the medium

imaging depth

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36
Q

four settings that affect temporal resolution

A
  1. maximum imaging depth
  2. # of pulses per scan line
  3. sector size
  4. line density
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37
Q

what results in high temporal resolutuion

A 
high frame rate
shallow imaging
fewer pulses per image
single focusing
narrow sector 
low line density
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38
Q

what results in low temporal resolution

A 
low frame rate 
deep imaging 
more pulses per image 
multifocusing
wide sector 
high line density ( improves spatial resolution)
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39
Q

what is the typical value of frame rate

A

20-100Hz

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40
Q

what is associated with a better movie but lower quality image

A

high temporal resolution

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41
Q

what is associated with a poor quality movie but high quality image

A

low temporal resolution

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42
Q

What are the six components of an ultrasound system

A 
master synchronizer
transducer 
pulser 
receiver 
display 
storage
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43
Q

what are the five functions of the receiver

A 
amplification
compensation
compression
demodulation
rejection
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44
Q

Higher frequency undergoes_________ TGC

A

more

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45
Q

Lower frequency undergoes ___________ TGC

A

less

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46
Q

what are the 5 requirements for contrast agents

A 
safe 
strong reflectors
long persistence
small enough to pass through capillaries
metabolically inert
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47
Q

what are the characteristics of Bistable displays

A 
2 choices, black or white
on or off
high contrast 
narrow dynamic range
poor contrast resolution
48
Q

what are the characteristics of gray scale displays

A 
many shades of gray
multiple levels
low contrast
wide dynamic range
good contrast resolution
49
Q

what are forms of preprocessing

A 
TGC
log compression
write magnification
fill in interpolation
persistence ( frame averaging)
spatial compounding
50
Q

what are forms of postprocessing

A

read magnification

3-D rendering

51
Q

give the order of information flow through the ultrasound system

A 
Master synchronizer
Pulser
Beam former
Transducer (preamplification)
Receiver
Scan converter
Display
Image archive (PACS)
52
Q

Read Magnification

A 
does not rescan, only reads image in memory
reads old data 
postprocessing
same line density
larger pixel
unchanged spatial resolution
unchanged temporal resolution
53
Q

Write Magnification

A

rescans and acquires new data, discards old image data
writes new data
preprocessing
increased line density
more pixels
improved spatial resolution
temporal resolution can change (Improved if image is shallow)

54
Q

Spatial compounding is created with different ____________and has ___________ temporal resolution

A

different views

reduced temporal resolution

55
Q

Temporal compounding (persistence) is created with different _________ and has _____________ temporal resolution

A

different times

reduces temporal resolution

56
Q

Frequency compounding is created with different ____________ and has ___________ temporal resolution

A

different frequency

unchanged temporal resolution

57
Q

Narrow dynamic range has

A

few choices
bistable (black and white)
high contrast

58
Q

Wide dynamic range has

A

many choices
gray scale
low contrast

59
Q

Transducers process data with the

A

widest dynamic range

60
Q

the recording device has data with the

A

narrowest dynamic range

61
Q

Pulsatile flow is

A

arterial
cardiac contraction
high rate
higher pressure

62
Q

Phasic flow is

A

venous
respiration
low rate
lower pressure

63
Q

Volume
how much?
volume/time
liters/ min

A

flow

64
Q

speed
how fast?
distance/ time
meters/ sec

A

velocity

65
Q

stenosis causes

A 
change in flow direction
increased velocity in the stenosis * highest velocity, low pressure at the lumen ( bernoullis principle
turbulent flow at exit
pressure gradient across the stenosis
loss of pulsatility in arterial flow
66
Q

what are the factors that determine resistance (ohms)

A
  1. Radius of the lumen
  2. Length
  3. VIscosity of fluid
67
Q

At the most narrowed location of stenosis (bernoullis principle)

A

velocity is the highest
kinetic energy is the highest
pressure is the lowest

68
Q

Hydrostatic pressure order

A

-50mmHg at fingertip with hand elevated above head
-30mmHg at head
0 mmHg at heart
50mmHg at waist
75mmHg at knee
100mmHg at ankle

69
Q

Vessels collapse when opposing vessel walls touch each other, blood pressure is zero

A

coaptation

70
Q

what is the equation for hydrostatic pressure

A

measured pressure= circulatory + hydrostatic

71
Q

During inspiration

A

diaphragm descends into abd
pressure in thorax decreases
venous flow from legs decreases
venous return to the heart increases

72
Q

During expiration

A

diaphragm ascends into thorax
pressure in the abd decreases
venous flow to the legs increases
venous return to the heart decreases

73
Q

Doppler shift=

A

Doppler shift = received frequency - transmitted frequency

74
Q

Doppler shift equation

A

Doppler Shift=2 x reflector speedx incident freq. x cos
———————————————————–
propagation speed

75
Q

equation for nyquist limit

A

Nyquist limit (KHz) = PRF/2

76
Q

what are the five ways to eliminate aliasing

A
  1. use CW DOPPLER
  2. use a low frequency transducer
  3. select a new view with a shallow sample volume
  4. increase the scale, same view
  5. baseline shift (for appearances only)
77
Q

small sample volume creates

A

clean, large window

78
Q

large sample volume creates

A

spectral broadening or fill in

79
Q

what kind of velocity does color doppler measure

A

mean/ average

80
Q

what kind of velocity does spectral Doppler measure

A

Peak velocity (CW AND PW)

81
Q

Imaging requires

A

normal incidence
higher frequency= better resolution
Pulsed wave only
1 Crystal

82
Q

Doppler requires

A

0 or 180 degrees incidence
lower frequency ( less aliasing)
pulsed or CW

83
Q

SMALL PACKETS HAVE

A

less accurate Doppler
less sensitive to low velocity
high frame rate, high temporal resolution

84
Q

LARGE PACKETS HAVE

A

more accurate
more sensitive to low velocities
low frame rate, low temporal

85
Q

Identifies high velocity jets anywhere along the length os the beam ( range ambiguitity)
no aliasing

A

Continuous wave Doppler

86
Q

accurately identifies the location of the flow (range resolution)
Good temporal resolution
Good range resolution
aliasing

A

Pulsed wave Doppler

87
Q

provides 2-D flow information directly on anatomic image
size of color jet is most affected by color Doppler Gain settings
Multiple packets= poor temporal resolution
Pulsed US
Range resolution
aliasing

A

Color Flow Doppler

88
Q

allows the use of color with low velocities or small volumes of blood flow
greatest sensitivity

A

Power Mode Doppler
Color angio
energy mode

89
Q

which spectral analysis is less accurate but faster

A

autocorrelation

90
Q

What are the things to do to optimize Color Doppler

A
  1. check if the angle (color box postition)
  2. check the color gain (gain)
    3, check the color scale (velocity scale)
91
Q

Eliminates low magnitude Doppler shifts that are created by moving anatomy rather than RBC’S

A

High pass wall filter

92
Q

serve as reject, exclude low level only Doppler shifts around the baseline, reject clutter

A

wall fillters

93
Q

what are the six basic assumptions of imaging systems

A
  1. sound travels in a straight line
  2. sound travels directly to a reflector and back
  3. sound travels at exactly 1,540m/s
  4. reflections arise from structures positioned along the beam’s main axis
  5. intensity of the reflections is related to the scattering characteristics of the tissue
  6. the imaging plane is extremely thin
94
Q

what kind of transducers create side lobe artifacts

A

mechanical

95
Q

what kind of transducers create grating lobe artifact

A

arrays

96
Q

how can one reduce grating lobes

A

with subdicing and apodization

97
Q

lobe artifacts degrade

A

lateral resolution

98
Q

linear array transducers have poor

A

elevational resolution

99
Q

cross talk is an artifact that happens in doppler only, what are the two causes

A

Doppler gain is set too high

incident angle near 90 degrees when flow is at the focus

100
Q

what are the requirements for quality assurance

A

multiple evaluations of the system’s components
repairs
preventative maintenance
record keeping

101
Q

what are the goal for quality assurance

A

proper equipment operation
detect gradual changes
minimize downtime
reduce number of repeat scans

102
Q

what are the methods of quality assurance

A

test under known, defined conditions
constant instrument settings
use phantom with measurable characteristics
image in identical environments

103
Q

a phantom is an

A

objective standard

104
Q

contains a medium similar to soft tissue, strategically located pins and structures that mimic cysts, masses . . .
evaluates gray scale

A

tissue equivalent phantom

105
Q

used to assess the accuracy of PW, CW, and color flow doppler
Vibrating strings and moving belt phantom

A

Doppler phantom

106
Q

Commercially available, array of strategically located pins
speed of soft tissue
does not have the same attenuating properties as soft tissue
cannot evaluate gray scale

A

AIUM 100mm Test Object- Water filled phantom

107
Q

measures the pressure in a sound beam

A

hydrophone

108
Q

a transducer which turns acoustic energy into heat

total heat gain+ time= total power

A

calorimeter

109
Q

measures the intensity at specific locations

A

thermocouple

110
Q

thermal index

A

bioeffects

111
Q

mechanical index

A

cavitation

112
Q

what 2 things are related to mechanical index

A

peak refraction pressure

lower frequency

113
Q

bubbles do not burst
shear stresses
microstreaming

A

stable cavitation

114
Q

formula for mechanical index

A

MI= Peak refraction pressure devided by the square root of frequency

115
Q

also known as normal, inertial( TIN)
bubbles burst
highly localized

A

transient

Fall 2014 study (9 decks)

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