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Sono 2343 > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

A mode

A

mode of operation in which the display presents echo amplitude versus depth (used in ophthalmology).

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2
Q

Amplification

A

the process by which small voltages are increased to larger ones.

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3
Q

Amplifier

A

a device that accomplishes amplification.

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4
Q

Analog

A

related to a procedure or system in which data are represented by proportional, continuously variable, physical quantities (e.g. electric voltage).

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5
Q

Analog-to-digital converter

A

a device that converts voltage amplitude to a number. Abbreviated ADC.

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6
Q

B mode

A

mode of operation in which the display presents a spot of appropriate brightness for each echo received by the transducer.

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7
Q

B scan

A

a B-mode image that represents an anatomic cross section through the scanning plane.

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8
Q

Beam former

A

the part of an instruement that accomplishes electronic beam scanning, apodization, steering, focusing,, and aperture with arrays.

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9
Q

Bistable

A

having two possible states (e.g. on or off, white or black, one or zero).

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10
Q

Bit

A

binary digit; one or zero.

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11
Q

Chanel

A

a single one or two-way path for transmitting electric signals, in distinction from other parallel paths; an independent transmission delay line and transducer element path; an independent reception transducer lement, amplifier, analog-to-digital converter, and delay line path.

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12
Q

Cine loop

A

sequential display of all the frames stored in memory at a controllable frame rate.

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13
Q

Coded excitation

A

a sophisticated form of transmission in which the driving voltage pulses have intrapulse variations in amplitude, frequency, and/or phase.

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14
Q

bandpass filter

A

f

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15
Q

Compensation

A

equalization of received echo amplitude differences caused by different attenuations for different reflector depths; also called depth gain compensation or time gain compensation.

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16
Q

Compression

A

reduction in differences between small and large amplitudes. Region of high density and pressure in a compressional wave.

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17
Q

Contrast resolution

A

ability of a gray-scale display to distinguish between echoes of slightly different intensities.

depends on the number of bits per pixel in the image memory

more bits per pixel = more gray

dynamic range, pre and post processing are functions that the operator can change to optimize the contrast resolution

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18
Q

Demodulation

A

detection.

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19
Q

Depth gain compensation

A

compensation. Abbreviated DGC.

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20
Q

Detection

A

conversion of voltage pulses from radio frequency to video form. Also called demodulation, amplitude detection, and envelop detection.

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21
Q

Digital

A

related to a procedure or system in which data are represented by numeric digits.

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22
Q

Digital-to-analog converter

A

a device that converts a number to a proportional voltage amplitude. Abbreviated DAC.

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23
Q

Display

A

a device that presents a visual image derived from voltages received from an image processor.

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24
Q

Dynamic range

A

ratio (in decibels) of largest to smallest power that a system can handle; ratio of the largest to smallest intensity of echoes encountered.

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25
Q

Elastography

A

imaging tissue stiffness by tracking movement under mechanical stress.

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26
Q

Flat-panel display

A

a backlighted rectangular matrix of thousands of liquid-crystal display elements.

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27
Q

Frame

A

a single image produced by one complete scan of the sound beam.

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28
Q

Frame rate

A

number of frames of echo information stored each second.

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29
Q

Freeze

A

constant display of one of the frames in memory.

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30
Q

Gain

A

ratio (in decibels) of amplifier output to input electric power.

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31
Q

Gray scale

A

range of brightnesses (gray levels) between white and black

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32
Q

Image memory

A

the part of the image processor where echo information is stored in image format.

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33
Q

Image processor

A

an electronic device that manipulates and prepares images for visual presentation.

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34
Q

Lateral gain control

A

gain controls that enable different gain values to be applied laterally across an image to compensate for differing attenuation values in different anatomic regions.

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35
Q

M mode

A

a B-mode presentation of changing reflector position (motion) versus time (used in echocardiography).

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36
Q

Panoramic imaging

A

the extension of the field of view beyond the normal limits of a transducer scan plane.

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37
Q

Persistence

A

averaging sequential frames together.

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38
Q

Physical beam

A

s

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39
Q

Picture archiving and communications systems

A

the system provides means for electronically communicating images and associated information to workstations and devices external to the sonographic instrument, the examining room, and even the building in which the scanning is done. Abbreviated PACS.

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40
Q

Pixel

A

picture element; the unit into which imaging information is divided for storage and display in a digital instrument.

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41
Q

Postprocessing

A

image processing done after storage in the memory.

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42
Q

Preprocessing

A

signal and image processing accomplished before storage in the memory.

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43
Q

Pulse-echo principle

A

pulse-echo technique.

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44
Q

Radio frequency

A

voltages representing echoes in cyclic form. Abbreviated RF.

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45
Q

Real-time

A

imaging with a rapid frame sequence display.

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46
Q

Real-time display

A

a display that, with a sufficient frame rate, appears to image moving structures or a changing scan plane continuously.

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47
Q

Refresh rate

A

the number of times each second that information is sent from the image memory to the display. The number of times per second that computer monitor redraws the information found in the memory.

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48
Q

Scan line

A

a line produced on a display that represents ultrasonic echoes returning from the body. A sonographic image is composed of many such lines.

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49
Q

Scanning

A

the sweeping of a sound beam through the anatomy to produce an image.

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50
Q

Shear wave

A

transverse wave.

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51
Q

Signal

A

information-bearing voltages in an electric circuit; an acoustic, visual, electric, or other conveyance of information. The physical representation of a message or information.

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52
Q

Signal processor

A

an electronic device that manipulates electric signals in preparation for appropriate presentation of information contained in them.

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53
Q

Spatial compounding

A

averaging of frames that view the anatomy from different angles.

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54
Q

Strain

A

the increase or decrease of the length of a segment of a material, subjected to as tress, divided by its original length

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55
Q

Stress

A

a force per unit area applied to a material that compresses or stretches it,

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56
Q

Temporal resolution

A

ability to distinguish closely spaced events in time; improves with increased frame rate.

time required to generate one frame

units are ms

depends on FR, depth, LPF, and foci

improves with higher FR

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57
Q

Time gain compensation

A

equalization of echo amplitude differences caused by different attenuations for different reflector depths; also called depth gain compensation. Abbreviated TGC.

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58
Q

Virtual beam

A

an imaginary beam (as opposed to aa physical ultrasound beam ) that describes the result of retrospective, computed beam forming, the virtual beam can be imagined in transmission or reception form.

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59
Q

Volume imaging

A

3D imaging.

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60
Q

Young’s modulus

A

a measure of the hardness (stiffness) of a material.

stress/strain

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61
Q

transmit power

A

controls the amplitude of excitation voltage which drives the crystals

a higher voltage = a higher amplitude sound wave

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62
Q

dynamic range

A

the ratio of the max to the min amplitude

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63
Q

signal

A

any phenomenon desired to be measured

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64
Q

noise

A

any unwanted signals

primarily from the electronics

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65
Q

noise floor

A

the amplitude level below which no signals are visible because of the presence of noise

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66
Q

SNR

A

amplitude of the signal/amplitude of the noise

specifies signal quality

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67
Q

in ultrasound the signals are

A

the reflections and doppler shifts

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68
Q

OP1 instruments are composed of what?

A

beam former
signal processor
image processor
display

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69
Q

beam former

A

where the action originates

consists of:
pulser
pulse delays
channels
T/R switch
amplifiers
digitizer
echo delays
summer
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70
Q

pulser

A

generates the voltages that drive the transducer

its frequency determines the frequency of the resulting ultrasound pulse

its PRF and PRP = the ultrasound’s PRF and PRP

1 ultrasound puls eis produced from each voltage pulse

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71
Q

to avoid misplacement, the following formula must hold true

A

penetration x PRF =< 77

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72
Q

pulse delays

A

along with the pulser carry out sequencing, phase delays, and variations in pulse amplitude

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73
Q

Transmit/receive switch

A

directs the driving voltages from pulse delays to the probe during transmission
and directs the returning echo voltages to the amplifiers during reception

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74
Q

amplifiers

A

increase voltage amplitude (called gain)
TGC
attenuation and max amplifier gain determines the max imaging depth
max amplifier is determined by noise
lateral gain controls are available in some systems

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75
Q

TGC compensates for what?

A

attenuation as depth increases

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76
Q

power (amplitude) ratio=

A

output power/input power

77
Q

digitizer

A

aka ADC (analog to digital converter)
echo voltages are digitized here
echo voltages are replaced by a series of numbers
interrogation rate must be 2x the highest frequency involved to persevere all harmonics
eg if the highest frequency is 5 mhz, the digitizing rate must be at least 10 mhz

78
Q

echo delays

A

digital delay lines that digitized echoes pass through to accomplish reception dynamic focus and steering

79
Q

summer

A

aka adder
combines all signals from all channels to create a scan line
reception apodization and dynamic aperture occur here

80
Q

transmission channels

A

pulser -> delay -> element

81
Q

reception channels

A

element -> amplifier -> ADC -> delay -> summer

82
Q

signal processor consists of

A

filtering/rejection
detection/demodulation
compression

83
Q

filter

A

tuned amplifiers reduce noise

eleminates frequencies outside the echo bandwidth while retaining the useful ones

uses a bandpass filter

84
Q

detection

A

aka demodulation

converts echo voltages from radio frequency to video form

the video retains the amplitudes of the echo voltages

85
Q

compression

A

reduces the dynamic range with selective amplification

reduces the difference between the smallest and largest amplitudes

86
Q

image processor

A

converts the serial scan line data into iimages that are stored in the image memory

87
Q

preprocessing

A

occurs before the echo data is stored in the image memory

88
Q

pixel interpolation

A

fills in missing pixels

assigns brightness value based on the average brightness of adjacent pixels

common in sector images
uncommon in linear images

89
Q

persistance

A

is the averaging of sequential frames to provide a smoother image and to reduce noise

speckle reduction, increases dynamic range and contrast resolution

decreases frame rate

not used for rapidly moving structures

90
Q

volume imaging (3D)

A

acquired by assembling 2D scans into a 3D volume of echo information in the image memory

4D imaging is 3D imaging in real-time
the 4th dimension is time

91
Q

image memory

A

after the echo data is preprocessed, the image frames are stored here

92
Q

freeze

A

displaying one frame out of a sequence

93
Q

cine loop

A

aka cine review, clip, loop, cine

last several frames stored before freezing

94
Q

pixels and bits

A

sonography memories are stored in numbers (binary)

the image is divided into pixels like a checkerboard

in a bit memory there’s 4 checkerboards back to back
each pixel has 4 bits
allows for numbers from 0-15
is a 16 shade memory

95
Q

ultrasound systems usuall have a ______ bit memory.

A

6, 7, or 8-bit memory

96
Q

the ___ the binary number, the ___ the pixel will be displayed

A

higher, brighter

97
Q

write zoom

A

occurs in preprocessing

uses all the pixels on a smaller region

98
Q

read zoom

A

occurs in postprocessing

enlarges pixels

99
Q

postprocessing

A

image processing done after the echoes are stored in the scan converter

determines how the echo data stored in the memory will appear on the display

white echo display is the one we use

100
Q

B color

A

ability to colorize echoes in different shades other than gray

101
Q

volume presentation

A

3D can be displayed in 2D slices, surface renderings, transparent view (x-ray view), etc.

102
Q

DAC

A

aka digital to analog converter

converts the digital data received from the image memory to analog voltages that are fed to the display to determine echo brightness

103
Q

display

A

the brightness is proportional to the echo strength

flat -panel display: presents image in horizontal lines from top to bottom

3 types:
B mode
A mode
M mode

104
Q

B - mode

A

brightness mode, gray scale, B scan

105
Q

M - mode

A

motion

used to show motion of cardiac

presents depth vs time

106
Q

A - mode

A

shows the amplitude in echoes

used in ophthalmology

presents depth vs amplitude

107
Q

temporal resolution

A

ability of a display to distinguish closely spaced events in time and to present rapidly moving structures correctly

improves when the FR increases because less time elapses between one frame to the next

108
Q

frame rate

A

the number of images stored in the image memory per second

109
Q

for each focus on each scan line in each frame a ___ is required.

A

pulse

110
Q

n x LPF x FR =

A

PRF

to increase the number of foci, the number of lines per frame, and the FR, the PRF must increase

111
Q

to avoid echo misplacement, all echoes from one pulse must

A

be received before the next pulse is emitted

112
Q

wider images and multiple foci reduce

A

the FR

113
Q

echo misplacement will occur if this equation doesn’t hold true

A

pen x n x LPF x FR =< 77,000 cm/s

77,000 is half of the average speed 1.54

114
Q

harmonic imaging

A

filtering in which the fundamental frequency echoes are filtered out and the second harmonic frequencies are accepted

harmonic beam is narrower (improves LR)

grating lobe artifacts are eliminated

AR is kept high by sending two pulses per scan line and inversing the second (pulse inversion)

FR decreases

115
Q

panoramic imaging

A

wider field of view like a panoramic photo

adds new info

done by sliding the probe

116
Q

spatial compounding

A

is the averaging of frames to view anatomy in different angles

reduces speckle and clutter

specular surfaces are presented more completely

structures previously hidden can be visualized

117
Q

elastography

A

presents qualitative or quantitative information regarding the stiffness of the tissue

displayed as color red = soft
blue = hard

118
Q

cardiac strain imaging

A

presents info regarding contraction and relaxation strain and strain rate information for the myocardium

119
Q

fusing imaging

A

combo of sonography imaging and another imaging like CT or MRI

120
Q

Major parts of the system

A

beam former
signal processor
image processor
display

121
Q

Beam former

A

found in array systems

consists of:
pulser
pulse delays
T/R switch
amplifier
ADCs
echo delays
sum
122
Q

pulser

A

produces electric voltages that drive the probe

forms the beam that goes into the tissue

informs receiver and memory when ultrasound pulses are made (for accurate display echo placement)

123
Q

ultrasound PRF is determine by what?

A

the voltage PRF of the pulser

124
Q

to avoid echo misplacement

A

all echoes from one pulse must be recieved before the next pulse is emitted

PRF must be adjusted
pen (cm) x PRF =< 77 cm/ms

125
Q

what determines the max A of the ultrasound pulse?

A

the pulser

the higher the voltage, the higher the max
which allows for higher system sensitivity

126
Q

pulse delays

A

assist the pulser

carry out sequencing, phasing, and amplitude variations

127
Q

what does pulse delays make possible?

A 
scanning
steering
transmission focusing
aperture variation
apodization
128
Q

coded excitation

A

when a series of pulses and gaps is used

allows multiple foci and separated harmonic bandwidth from frequency pulse bandwidth

increases penatration and contrast resolution

decreases speckle

allows B flow (gray scale imaging of blood flow)

129
Q

the more channels, the more ___ of the beam

A

control

there’s separate transmit and receive channels
usually 64-192 channels in modern equipment
usually no more channels than the number of elements

130
Q

T/R switch

A

transmit/receive switch

directs voltages from pulse delay to probe

directs echo voltages from probe to amplifiers

protects amplifiers from the large driving voltages of the pulser

131
Q

amplifiers

A

increase voltage amplitude

132
Q

pre-amplifiers

A

boosts strength of all voltages to prevent them from being lost and sends them to the receiver

can be located in scanner or probe assembly

133
Q

receiver gain

A

the ratio of amplifier output to electric power input

units are dB

134
Q

overall gain

A

the ratio of ooutput signal strength to input signal strength

controlled by us

135
Q

compensation

A

allows graded amplification according to depth of the echoes within the image
controlled by us
later GC exists (compensates for outer edges)
LIKE TISSUES SHOULD APPEAR LIKE REGARDLESS OF DEPTH

136
Q

compensation is also called

A

TGC transmit gain compensation, DGC depth gain compensation, SGC swept gain compensation

137
Q

SNR

A

signal to noise ratio

you want the signal to have high amplitude and the noise to have low amplitude

we want the difference in A between the two to be large

138
Q

does increasing reciever gain improve SNR

A

NO

because both signals and noise are being boost equally

139
Q

apparent SNR

A

how it looks to our eyes

140
Q

how to improve SNR

A

increase transmit power

decrease frequency for deeper depths

use different imaging plane

maneuvers to remove attenuation

move transmit focus deeper

use larger aperture for deeper focus

use semi-invasive techniques like endoprobes

141
Q

HID formula

A

6/f
or
3/attenuation coefficient

142
Q

depth determines what and why?

A

the PRF because of the time it takes echoes to return

143
Q

CRT

A

cathode ray tube
type of monitor
old times

144
Q

Digitizer

A

aka ADC

converts analog (proportional) signal to digital (discrete numbers)

the rate at which sampling occurs can affect the digital signal accurateness representing the analog signal

digital output is in binary (bits)

145
Q

faster signals need ___ sampling

A

faster

146
Q

what does it mean when something is aliased?

A

when we lose info bc of sampling rate made the (reconstructed) output signal different from the (original) input signal

147
Q

nyquist criterion

A

to avoid aliasing, the sample frequency must be AT LEAST twice as fast as the highest frequency in the signal

sampling frequency (min) = 2 x signal frequency (max

148
Q

echo delays

A

digital delay lines which accomplish reception dynamic focus and steering

149
Q

summer

A

aka adder

last component of the beam former

is where all the channels signals are combined to form a scan line

reception apodization and dynamic aperture are accomplished here

150
Q

Signal processor

A

filtering, demodulation (detection), and compression happen here

151
Q

filter

A

tuned amplifiers are used to reduce noise in electronics by using a bandpass filter

keeps most signal frequencies and rejects noise frequencies outside of it

152
Q

tuned amplifier

A

amplifier which has an electronic bandpass filter

153
Q

bandpass filter

A

passes a range of frequencies and rejects those outside the acceptance bandwidth

154
Q

compression

A

reduces dynamic range to the dynamic range of the monitor and our eyes

the echo amplitudes undergo compression in which they’re logarithmically amplified

weaker echoes are amplified more than stronger ones

compression reduces the difference between the smallest and the largest echo voltage amplitudes

can result in loss of info/signals

155
Q

dynamic range

A

is the ratio of the largest amplitude to the smallest amplitude signal that a system can process

max dynamic range is determined by the electrical capacity of the system

156
Q

detection/demodulation

A

is the process of converting the radio frequency signal to video form

amplitude remains the same

includes rectification and smoothing

when sound goes into the body, the body changes/modulates the signal

these changes are detected by detection/demodluation

echo voltages from the probe are in radio frequency form which are too big and difficult to store and display

157
Q

rectification

A

converts the negative components of a signal into positive components so that all components are positive (unipolar)

158
Q

smoothing

A

aka envelope detection or amplitude detection

is the conversion of voltage pulses from radio frequency to video form

retains signal amplitudes

traces the signal peaks and valleys while applying some averaging/smoothing

rejection is part of this

159
Q

rejection

A

aka suppression or threshold

eliminates voltage pulses with an amplitude below the rejection level

these low echoes are produced by side and grating lobes

can be adjusted by operator

160
Q

image processor

A

converts the serial scan line data into images which are processed before and after storage in the image memory in order to prepare the images for display

consists of:
preprocessor
scan converter
image memory
postprocessor
DAC
161
Q

preprocessing

A

any processing done to echoes before they are stored in the scan converter

includes:
edge enhancement
pixel interpolation
persistence
volume imaging (3D)

can be changed only in real-time, not on freeze mode

162
Q

postprocessing

A

can be applied in real-time and freeze mode

163
Q

tissue texture preprocessing

A

done preprocessing

different gray-scale assignments result in subtle texture changes in the image

164
Q

edge enhancement

A

sharpens boundaries of reflectors to make them more detectable and for measurements to be more accurate

165
Q

pixel interpolation

A

filling in of missing pixels to increase the image quality

assigned brightness value is determined by averaging adjacent values

performed more commonly in sector formats

166
Q

persistance

A

averaging of sequential frames (temporal averaging) to provide a smoother image

reduces noise (primarily speckle because it’s random)

decreases FR and temporal resolution

improves SNR

167
Q

volume imaging

A

slices reformatted into 3D

when performed at rates of 30 per sec, it is real time imaging aka 4D imaging

168
Q

scan converter

A

is the memory of the system

formats echo data into image form for processing, storage, and display

modern ultrasound machines use digital scan converters (DSC) which allows the info to be displayed in linear or sector format

produces the framers for storage and display

169
Q

digital memory operates in what kind of system?

A

binary numbers

170
Q

digital scan converter

A

obtains 2 quantities for each echo signal

obtains the echo signal’s memory storage address

obtains the echo signal’s amplitude value in binary number form.

171
Q

address

A

is the signal location

signal is placed in a location in the computer memory matrix according to its address

address is determined by round trip time of the echo (calculated by the range equation)

to determine distance from source to reflector, the propagation speed in the medium must be known or assumed and round trip time is measured

172
Q

image memory

A

each frame is stored in the memory after the data has been converted into image form by the scan converter

when freeze is on there’s no transmission or reception

173
Q

digital memory

A

only the distance to reflector is needed, that’s why the range equation has the o.5

after the distance is calculated, the voltage level of each echo amplitude is given a value and placed at its address

multiple layers of matrices exist in the memory and is used to create different shades of gray

binary number combo allotted to each pixel location corresponds to echo amplitude received for that address

the higher the binary number, the higher the amplitude stored in the matrix

each bit combo is assigned a corresponding display brightness level

most systems display 64 shades (dynamic range of human eye)

174
Q

memory-bit depth

A

aka multiple layers of matrices or memory resolution

6-8 bit depth memory is most common for ultrasound systems

175
Q

the DSC stores ___ of image data in ___ format

A

the DSC stores bits of image data in matrix format

typically consists of 512 x 512 pixels

176
Q

__ bits = 1 byte

A

8 bits

177
Q

__ bytes = 1 kilobyte

A

1024 bytes

178
Q

color tints can be differentiated by our eyes more than ___?

A

grays

179
Q

3D representations vs acquisition

A

acquisition is preprocessing

representations is postprocessing

180
Q

DAC

A

digital to analog converter

after the images are stored in memory and postprocessed

digital numbers are retrieved and converted into voltages that determine the brightness of echoes on display

181
Q

CRT

A

cathode ray tube
old times
very large

made a display with an electron beam that painted horizontal lines which corresponded to rows of echo information

had a phosphor-coated face and a bright spot

182
Q

flat panel

A

modern

uses backlit LCD

183
Q

SVGA

A

super video graphics array

pixel matrix is 1024 x 768 and refresh rate is 60 Hz

184
Q

LCD

A

liquid crystal display

composed of rectangular matrix with thousands of LCD elements which be turned on or off individually to pass or block light

each element can be turned on to a certain degree to allow a measured amount of light to pass through

256 levels of luminance (displayed grays)

1024x768 matrix pixels

185
Q

PRF

A

a pulse is requried for each focus on each scan line in each frame

PRF=nxLPFxFR

decreases as pen increases
pen=nxLPFxFR=<77,000 cm/s

186
Q

frame rate

A

decreases with increasing depth or multiple foci since it requires more time to make each frame

increase as field of view is narrowed, requiring fewer scan lines per frame

187
Q

output devices

A

vcrs
printers
digital devices like hard drives and usbs

188
Q

storage formats

A

JPEG Joint Photographic Experts Groups

TIFF Tagged Image File Format

AVI audio-video interweaver

MPEG Moving Picture Experts Group

if file size increase, quality increases and vice versa

189
Q

DICOM

A

standardized protocol

digital imaging and communications in Medicine

included in PACS

Sono 2343 (8 decks)

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