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Physics 2 > Midterm > Flashcards

Midterm Flashcards

1
Q

what are we dealing with at the signal processor?

A

digital signals

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2
Q

what does the reception channel of the beam former do?

A

amplifies and combines echo voltages from individual elements and sends them to the signal processor

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3
Q

what are the functions of the signal processor?

A
  • filtering
  • detection
  • compression
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4
Q

what is bandwidth?

A

range of frequencies contained in a pulse

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5
Q

what does pulsed wave ultrasound produce?

A

a bandwidth of transmitted frequencies

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6
Q

what is the strongest frequency?

A

fundamental frequency

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7
Q

do we have a bandwidth of returning echo frequencies?

A

yes

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8
Q

filtering

A

getting rid of frequencies we don’t want

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9
Q

what does filtering reject?

A

frequencies above or below bandwidth

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10
Q

how does filtering happen?

A

done with BANDPASS filters

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11
Q

what are the 2 filters?

A

tuned amplifier

dynamic filter

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12
Q

tuned amplifier

A

involves an amplifier with a filter attached

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13
Q

dynamic filter

A

a filter that can be adjusted

ex. harmonic frequencies

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14
Q

harmonics

A

modification of the sinusoidal waveform as it propagates through tissue

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15
Q

in harmonics what are multiple frequencies produced by

A

fundamental frequency (odd and even multiples)

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16
Q

If we have a fo of 5MHz what are the odd harmonic frequencies?

A

15 MHZ

25 MHZ

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17
Q

If we have a fo of 5MHz what are the even harmonic frequencies?

A

10 MHz
20 MHz
30 MHz

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18
Q

what is your first harmonic named?

A

fundamental frequency

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19
Q

what is the 2nd harmonic frequency?

A

will produce echoes that will allow for better resolution

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20
Q

what function do filters in signal processor preform?

A

harmonics

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21
Q

in harmonics, what echoes are received?

A

echoes from fo and 2fo

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22
Q

what happens to the fundamental frequency at the signal processor?

A

it is filtered out (this happens when we press THI)

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23
Q

what are the benefits of harmonics with a narrower beam?

A
  • better lateral resolution

- better elevational resolution (thinner)

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24
Q

what are benefits of harmonics?

A
  • narrower beam
  • side/grading lobes eliminated
  • reduction in anterior reverberation
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25
Q

anterior reverberation (AKA. main bang)

A

reflections between the transducer face and skin surface cause multiple horizontal lines of echoes to appear in near field

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26
Q

where can anterior reverberation also occur?

A

ribs

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27
Q

harmonics cause beam to be generated further into the tissue, what does it have a less chance of?

A

anterior reverb-main bang echoes are filtered out

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28
Q

summarizing all the points, what are the benefits of harmonics?

A
  • better detail resolution (lateral and elevational)

- reduced artifacts (grading lobes and anterior reverberation)

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29
Q

what are the drawbacks of harmonics?

A
  • decreased penetration

- worse axial resolution

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30
Q

why is there a decrease in penetration in harmonics?

A

higher frequency means more attenuation

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31
Q

what must the transducer fit into?

A

the bandwidths of both fo and 2fo

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32
Q

harmonics allow for better ________ overall

A

resolution

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33
Q

what do narrower bandwidths for harmonic frequenxy?

A
  • longer SPL
  • larger (worse) AR
  • worse resolution
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34
Q

what helps with the drawbacks narrow bandwidth?

A

pulse inversion harmonic imaging

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35
Q

what is pulse inversion harmonic imaging?

A

2 pulses are sent out back to back

  • regular pulse
  • inverted pulse
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36
Q

where are harmonic signals produced?

A

In the tissue

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37
Q

what happens to the echo of the fundamental signal?

A

destructive interference

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38
Q

what happens to the echo of the harmonic signal?

A

sinusoidal signal

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39
Q

what happens to the fundamental signal in pulse inversion harmonic imaging?

A

does not make it back

-transducer can use its entire bandwidth for 2 fo

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40
Q

what is the wider bandwidth for harmonic frequency?

A
  • shorter SPL
  • smaller (better) AR
  • better resolution
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41
Q

what does sending multiple pulses decrease?

A

Frame Rate

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42
Q

what is another name for detection?

A

demodulation

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43
Q

what is video form/amplitude form more useful for?

A

processing

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44
Q

what is detection?

A

radio frequency form to video form/ amplitude form

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45
Q

what is not an operator controlled function?

A

detection

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46
Q

what is voltage amplitudes proportional to?

A

intensity of returning echoes

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47
Q

what are the 2 steps to detection?

A
  1. rectification

2. smoothing

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48
Q

reactivation

A

turns negative voltages into positive voltages

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49
Q

smoothing

A

warps an envelope around the signal to make it less bumpy

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50
Q

video form

A

we only require the maximum values of the signal

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51
Q

what preforms dynamic range function?

A

compression

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52
Q

dynamic range

A

power ratio of largest to smallest amplitude that system can handle

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53
Q

what does dynamic range equal?

A

power ratio

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54
Q

what does 60 dB DR mean?

A

means the strongest echo is 10’6 stronger than the weakest echo

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55
Q

power ratio=

A

voltage ratio’2

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56
Q

what can amplifiers handle?

A

DR 100-170 dB

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57
Q

what can the display handle?

A

30 dB

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58
Q

what can our human vision handle?

A

20 dB

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59
Q

for us to view the highest brightness how much higher must the DR be?

A

can only be 100 times the lowest

60
Q

compression

A

the process of decreasing the differences between the smallest and the largest echo amplitudes to a useable range

61
Q

which signals are more amplified?

A

weaker signals

62
Q

what does compression do?

A

reduces dynamic range with selective amplification

63
Q

what does compression mean for us?

A

contribute to contrast resolution

64
Q

contrast resolution

A

being able to separate 2 different echoes as 2 different shades of grey

65
Q

what does compression effect?

A

our contrast

66
Q

is compression operator controlled/

A

yes, DR button

67
Q

what does the decrease in DR do to contrast?

A

more contrast=grainer

68
Q

what does the increase in DR to do contrast?

A

less contrast=smoother

69
Q

what are the functions of the signal processor?

A
  • bandpass filtering
  • amplitude detection
  • compression (dynamic range reduction)
70
Q

what are the components if the image processor?

A
  • preprocessor
  • scan converter
  • image memory
  • postprocessor
  • digital-to-analog converter
71
Q

scan line information is:

A
  • built into frames of information

- pre-processed

72
Q

what is stored in the image memory?

A

frames

73
Q

frames can be pulled out of memory and:

A
  • post-processed

- sent to display as an analog signal

74
Q

what is scan conversion done by?

A

scan converter

75
Q

scan conversion

A

building a frame

Echo information-scan lines (digital) to image form-frames (digital)

76
Q

how many scan lines are in a frame?

A

96-256 lines in a frame

77
Q

pixels

A

each frame is made up of a ‘matrix’ of tiny blocks called pixels

78
Q

more pixels=

A

better resolution

79
Q

what are common matrix?

A
  • 1024 x 768 matrix

- 512 x 384 matrix

80
Q

3D=

A

voxels

81
Q

what do frames require?

A

processing

82
Q

pre processing

A
  • Done while echo data is being stored in the memory

- The frame is still being built during this time

83
Q

post-processing

A

done on image retrieved from image memory

84
Q

when does pre processing function?

A

before (while) the data is stored in image memory

85
Q

when does post processing function?

A

after the data is stored in the image

86
Q

preprocessing info

A
  • persistence
  • panoramic
  • 3D & 4D
  • spatial compounding
  • write magnification
87
Q

post processing info

A
  • B colour
  • Freeze Frame
  • Black/white image inversion
  • read magnification
  • contrast variation
88
Q

what does pre/post depend on?

A

the manufacturer

89
Q

what does pre-processing do to the edges?

A

edge enhancement-sharpens boundaries to make them more detectable and make measurements more precise

90
Q

pixel interpolation

A

filling in missed pixels

-Average the brightness of the adjacent pixels and fill in the missing pixel accordingly

91
Q

Panoramic Imaging

A

compilation of frames as transducer is moved

92
Q

what does panoramic imaging result in?

A

an image with a wider field of view

93
Q

spatial compounding

A

hit the same object from different angles and average the images (trying to hit at 90 degrees)

94
Q

what does spatial compounding do?

A

clear out cysts

sharpen borders

95
Q

persistence (frame averaging)

A
  • averaging of sequential frames (in times)

- reduces noise (speckle) and random content

96
Q

what does persistence do to frame rate?

A

decrease

operator controlled

97
Q

3D imaging

A

multiple parallel 2D frames obtained and built into 3D volume

98
Q

elastography

A

imaging method that presents qualitative tissue stiffness information on the anatomic display and in some cases, presents quantitative stiffness information

99
Q

what is used when presenting elastogrpahy?

A

split screen

100
Q

what does colour side of electrography display?

A

compressibility

101
Q

what does compressibility have a correlation with?

A

malignancy potential

102
Q

what is pre-processing summary?

A

-all processing functions involved before frames are placed in memory
-they are all live-scanning options
CANNOT BE DONE AFTER PRESSING FREEZE

103
Q

post processing summary?

A

-involves processing done to an image after it is pulled from the image memory
CAN BE DONE ON A FROZEN IMAGE

104
Q

how many shades of grey and shades of colour can human eye see?

A

100 shades of grey

256 shades of colour

105
Q

Read Magnifaction (read zoom)

A

pulls out specific pixels from the frame from memory and displays them using the entire display

106
Q

what is the drawback of read magnification?

A

pixelization-enlargement of pixels

107
Q

Write Magnification (write zoom)

A

smaller field of view is written using the pixels for the entire frame
-better resolution

108
Q

what is another adjustment to write zoom?

A

changing depth

109
Q

what is scan line information built into?

A

frames of information

110
Q

describe scan line info process

A
  • buildt into frames of information
  • pre-processed
  • frames are stored in image memory
  • pulled out of memory
  • post-processed
  • sent to display as analog signal
111
Q

what is each image stored as?

A

a frame of information (this is a continuous process)

112
Q

what is another term for image memory?

A

digital memory

113
Q

freeze frame

A

displays latest image stored in memory

114
Q

cineloop

A

displays last 100-130 images

115
Q

what information does each pixel conatin?

A

brightness (intensity/amplitude) at a particular anatomical postition

116
Q

numbers are stores in the memory elements (pixels) according to what?

A

the intensity of the echoes received from corresponding anatomic location

117
Q

how many shades of grey can one matrix (checkerboard) show?

A

2 shades (on and off)

118
Q

what do more shades of grey require?

A

more matrixes (more bits)

119
Q

how many options would you have with a 1-bit pixel?

A

2 options (0/1)

120
Q

bistable

A

1-bit pixel

121
Q

what is represented when memory element is off?

A

0 so the picture is black (on would be 1 and white)

122
Q

multiple bits

A

binary digit

123
Q

bit depth/capacity

A

how many options for black/white/grey

124
Q

what is the bit depth for a 3 bit pixel?

A

8 possible shades of grey

125
Q

2’8

A

256 possible shades of grey

126
Q

if you have a 7 bit pixel (128 shades) how many options does each pixel have?

A

0-127

127
Q

how many bit memories does a majority of ultrasound machines currently use?

A

6-8

128
Q

how many shades of grey can humans see in?

A

100 shades

129
Q

more pixels=

A

more shades of grey

130
Q

what is the binary number system?

A

alternative to the decimal (Arabic) number system

131
Q

CR=

A

dB/shade

132
Q

contrast resolution

A

being able to separate 2 different echoes as 2 different shades of grey

133
Q

what affects our DR?

A

compression reduces the DR for us so we wouldn’t have as many different amplitudes to deal with

134
Q

what is the next step after compression?

A

group those intensities into the available shades of grey

135
Q

if we have more bits what does that do to our contrast resolution?

A

better contrast resolution

136
Q

what affects our contrast?

A

bits/pixels

137
Q

is contrast operator controlled?

A

no it is manufacturer dependant

138
Q

less shades=

A
  • more contrast
  • grainier
  • lower DR
139
Q

more shades=

A
  • less contrast
  • smoother
  • higher DR
140
Q

contrast reolution=

A

DR/bits-per-pixel

141
Q

more bits/pixels=

more pixels/frame=

A

better CONTRAST resolution

better DETAIL resolution

142
Q

1 byte=

A

8 bits

143
Q

1 kilobyte

A

1024 bytes

144
Q

when is a frame ready to be sent to the display?

A

once it is pre-processed, stored in the image memory, pulled from the image memory, and post-processed

145
Q

digital memory (#’s)=

A

voltages for display

Physics 2 (4 decks)

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