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CT Physics > Test 2 Introduction to Computers > Flashcards

Test 2 Introduction to Computers Flashcards

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1
Q

Nvm

A

Nvm

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2
Q

Early computers in 1951-1958 relied on ______________ memory.

A

vacuum tube

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3
Q

Early computers in 195-1958 are associated with _________ and ___________.

A

punch cards and magnetic tape

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4
Q

What were the disadvantages of vacuum tubes for electronic computer technology?

A

warm-up

ran hot (required constant heating and required air for conditioning)

frequent failures

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5
Q

Computers after vacuum tubes (1959-1963) utilize _____________ and _________________ memory.

A

transistor and magnetic core

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6
Q

Computers after vacuum tubes (1959-1963) had the advantage of _____________ (2).

A

being smaller

required less power

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7
Q

Discrete semiconductor components in computers utilized _________ and ___________.

A

magnetic memory cores and transistors

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8
Q

discrete semiconductor components had the advantages of:

A

being smaller and cooler than vacuum tubes

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9
Q

“millions of semiconductor components in a tiny package” describes _______________.

A

an integrated circuit

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10
Q

What are the advantages of integrated circuits?

A

lowered production costs

extremely small

extremely fast

run very cool

very reliable

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11
Q

What are the four categories of computers?

A

super computers

mainframes

minicomputers

microcomputers

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12
Q

______________ are:

large (even today)

expensive

found only in major research sites

applications include weather, scientific modeling, oil exploration, and other research

A

supercomputers

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13
Q

______________are:

large

very expensive

requires a team of experts

takes a large number of users

applications include large corporation, government, and hospital usage

A

mainframe computers

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14
Q

__________ are:

“pc”

rapidly changing

low cost

non proprietary

first common in 1980s

A

microcomputer

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15
Q

when were microcomputers FIRST seen?

A

1970s

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16
Q

What computer is used for CT and why?

A

microcomputer:

size and price

imaging reconstruction and archiving

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17
Q

What are the three basic phases of how computers work?

A

input

processing

output

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18
Q

What are the possible inputs for a computer?

A

manual:
keyboard and mouse

Electronic:
CT detectors and barcode reader

Other:
Voice recognition

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19
Q

What is A to D?

A

Analog to digital conversion

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20
Q

Analog is ___________ varying.

A

continuously

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21
Q

Digital is _________ varying.

A

discretely

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22
Q

Computers require __________ input.

A

digital

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23
Q

Many real world inputs are _________ voltages.

A

analog

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24
Q

What is an example of an analog input?

A

CT detector intensity

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25
Q

Analog values must be converted to a ____ to use in a computer.

A

number

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26
Q

What is a CPU?

A

central processing unit

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27
Q

What does a CPU use?

A

arithmetic

logic

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28
Q

Internal memory is associated with:

A

scratchpad

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29
Q

What are possible outputs?

A

hard copy:
printer

soft copy:
monitor

Storage:
tape
disk

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30
Q

A _________ device does not lose information when power is shut off.

A

hardcopy

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31
Q

What is an example of a hard copy device?

A

a printer

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32
Q

A _________ device loses information when power is shut off.

A

softcopy

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33
Q

What is an example of a soft copy device?

A

monitor

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34
Q

What is D to A?

A

digital to analog conversion

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35
Q

What would be an example of D to A?

A

CT computer reconstructs digital image (an array of numbers) to an analog image

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36
Q

What are the three computer system elements?

A

hardware

software

people

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37
Q

What are the examples of hardware?

A

computer
monitor
disk drive
peripherals:
keyboard, mouse, printer

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38
Q

What is RAM?

A

Random Access Memory

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39
Q

_________ loses memory when powers off.

A

RAM

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40
Q

What is ROM?

A

Read Only Memory

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41
Q

__________ retains memory when powers off.

A

ROM

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42
Q

instructions to the computer like an operating system are _______.

A

software

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43
Q

_______________ is:

fundamental instruction to hardware

what to do when the computer first turns on

how to interact with hardware
(monitor, keyboard, mouse, flash drive)

computer “face”
(windows, Mac OS, Linux)

dictates how users interact with computer to run application software

A

operating system

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44
Q

Computer instructions which perform some desire task is ________.

A

application software

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45
Q

_______ is written in quasi English language. Examples are:

A

application software;

basic
HTML
COBOL
C

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46
Q

The people involved in computer systems are:

A

designers:
hardware and software

users:
run applications
provide input
use output

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47
Q

______ access hardware is characterized by any data can be accessed at any time, such as disks.

A

Direct (random)

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48
Q

_______ access hardware has data that only can be accessed in serial fashion, must pass through unwanted data to reach target, such as tapes. (the information in tapes is encoded magnetically). This is an obsolete hardware form.

A

Sequential

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49
Q

What are the two types of data storage technologies?

A

on site

remote

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50
Q

________ is data transmission between computers.

A

data transmission

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51
Q

What is network topology?

A

wiring scheme

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52
Q

What are examples of data communication technologies?

A

telephone lines
coaxial cable
fiber optic cable
microwaves
satellites
radio waves

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53
Q

What is LAN?

A

local area network

computers connected in one area
LANs can be connected together

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54
Q

What is WAN?

A

Wide area network
computers connected together over large distances

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55
Q

What are the two types of communication protocols for networks?

A

ethernet (uses bus technology)

internet

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56
Q

___________ is a special computer which handles shared functions for connected computers.

A

file server

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57
Q

A _________ may limit access to selected files/ directories by user, number of connections per user, and times when network available by user

A

file server

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58
Q

Digitizing a picture occurs when a commercial scanner renders a ______ into _______-.

A

photograph into numbers

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59
Q

What is the method for digital image formation?

A

place mesh over image

assign each square (pixel) a value based on density

pixel values form the digital image

each pixel assigned a value

value averages entire pixel

the larger the pixel, the more variation

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60
Q

The finer the mesh (sampling), the _____ accurate the digital rendering.

A

more

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61
Q

The _______ is the fundamental unit of computer storage.

A

bit

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62
Q

The _____ has only 2 allowable values, 0 and 1.

A

bit

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63
Q

Computers do all operations with __ and ___.

A

0s and 1s

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64
Q

A ___ is the smallest binary unit. It can only have a value of 0 or 1.

A

bit

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65
Q

A ____ has 8 bits. 2^8th power= 256 unique values.

A

byte

66
Q

A _____ has 16 bits. 2^16th power has 65536 unique values.

A

word

67
Q

A _______ has 32 binary bits.

A

double word

68
Q

How many values can be represented by one bit?

A

2 unique combinations

69
Q

How many values can be represented by 2 bits?

A

4 unique combinations

70
Q

How many values can be represented by 3 bits?

A

8 unique combinations

71
Q

______ controls the number of possible values a pixel can have.

A

bit depth

72
Q

Increasing bit depth results in:

A

more possible values for a pixel

better contrast resolution

73
Q

The more possible values for a pixel, the more gray shades and the better the _____.

A

contrast

74
Q

______________ involves assigning a number corresponding to image darkness at intervals along a line.

A

digitizing an image

75
Q

Digital image formation quantization is also known as:

A

A to D conversion

76
Q

_________ is the process of assigning a number to a gray shade. (only discrete numbers assigned).

A

digital image formation quantization

77
Q

What is a disadvantage of digital image formation quantization?

A

Can lose information because of discrete number assignment (averaging between values)

78
Q

True or false: an A to D converter will assign a value between 88 and 89 as 88.5.

A

False: it will either assign it as 88 or 89.

79
Q

_______ is the difference in x ray attenuation required for 2 pixels to be assigned different digital values.

A

contrast resolution

80
Q

In the setting pixel values graph, the y value is ______.

A

contrast resolution.

81
Q

The more values for a pixel:

A

the more shades of gray image can be stored in digital image

the less difference between x ray attenuation required to guarantee different pixel values

82
Q

What are display limitations?

A

not possible to display all shades of gray simultaneously

window and level controls determine how pixel values are mapped to gray shades

numbers (pixel values) do not change; window and level only change gray shade mapping

83
Q

________ changes the gray scale but not the pixel values.

A

window level

84
Q

________ is assignment of values to a pixel, while ________ is when each pixel value is assigned a brightness.

A

pre processing

post processing

85
Q

What are digital image sources?

A

CT
MRI
CR
DR
digital subtraction angiography
ultrasound
nuclear medicine

86
Q

What is compression?

A

reduction of image size in computer

87
Q

Why digital images?

A

image manipulation

enhancement

analysis

88
Q

What are the three image processing techniques?

A

point operations

spatial frequency filtering

geometric operations

89
Q

____________:

value of each pixel altered according to some rule

new pixel values assigned on pixel by pixel basis (independent of adjoining pixels)

A

point operations

90
Q

Local operations are also known as:

A

area processes

group processes

91
Q

__________ is the modification on input pixel based upon values of pixels close by.

A

local operations

92
Q

________________ is described by:

brightness changes rapidly with distance

small pixels are required

A

high frequency image

93
Q

________________ is described by:

brightness changes slowly with distance

A

low frequency image

94
Q

______________

can increase or decrease brightness changes with distance

Increasing:
sharpens image
increases noise

Decreasing:
blurs image
smoothes image
decreases noise

A

spatial frequency filtering

95
Q

What are the geometric operations?

A

scaling

sizing

rotation

translation

modifies (orientation of pixels) + (spatial position of pixels)

96
Q

Image memory

image processor

digital to analog converter

and host computer

are:

A

image processing hardware

97
Q

______ is temporary storage used while processing/ displaying image.

A

image memory

98
Q

___________ is the computer responsible for processing (arithmetic) done on input digital image.

A

image processor

99
Q

_______ converts output pixel values from look up table to analog voltage required by monitor.

A

digital to analog converter

100
Q

____________ directs image processing hardware, holds stored images, and directs archiving.

A

host computer

101
Q

_________ quantifies image blurring.

A

CT Spatial resolution

102
Q

_____________ is the minimum separation required between two high contrast objects for them to be resolves as two objects.

A

CT spatial resolution

103
Q

_______ is the ability of an imaging system to demonstrate small changes in tissue contrast.

A

contrast resolution

104
Q

_________ is the difference in contrast necessary to resolve two large areas in image as separate structures.

A

contrast resolution

105
Q

________________ is the difference in x-ray intensity transmitted through various parts of subject.

A

subject contrast

106
Q

___________ depends on:

thickness difference

density difference

atomic number difference

radiation quality (kVp, HVL)

A

subject contrast

107
Q

What are the limitations of radiography?

A

3D body rendered in 2D

structures superimposed on image

multiple views used to adequately visualize structure

density (gray shade) dictated by total attenuation by beam

thin highly attenuating objects have same density as thicker low attenuating object.

108
Q

What is superimposition?

A

a structure of interest viewed through underlying/ overlying structures

109
Q

How does radiography compare to CT?

A

Both based on differential attenuation
of x-rays passing through body

 Radiography
“Shadowgraph” using x-ray light source

 CT
Cross-sectional image
Image computed from pencil beam
intensity measurements through only
slice of interest
No superposition since all objects on
same slim

110
Q

What is an advantage of CT over radiography?

A

view anatomy without looking through underlying or overlying structures and improved contrast

111
Q

What are the benefits of tightly collimated beam of a CT machine?

A

minimizes scattered radiation

improves contrast

112
Q

In _________ there are very small contrast differences visible.***

A

CT

113
Q

Application examples of __________ are IVP and Inner ear.

A

conventional (not computed) tomography

114
Q

_____________ is:

not CT

body section imaging

popularity decreased by CT and MRI

A

Body section tomography

115
Q

What is the goal of body section tomography?

A

keep plane of interest in focus

blur all other planes (enhances contrast)

116
Q

Conventional tomography images are produced on:

A

films

117
Q

Why does conventional tomography cause blurring?

A

objects above or below fulcrum plane change position on film and thus blur.

118
Q

What are the disadvantages/ limitations of conventional CT?

A

overlying/underlying structures blurred, not removed

5-10% subject contrast difference required for objects to appear different (many anatomic systems don’t have this much subject contrast)

119
Q

What are the advantages of CT?

A

excellent low contrast resolution

120
Q

Why is CT able to create excellent low contrast resolution?

A

sensitive detectors

small beam size produces little scatter

much better than film

121
Q

What are the disadvantages of CT?

A

poorer spatial resolution than radiography

higher dose

artifacts at abrupt transitions
(bone/soft tissue interfaces and metallic objects)

122
Q

Describe early CT scanners.

A

4 minute scans of 1 slice

5 minute reconstruction

80 x 80 matrix

head only (water bag fit tightly around head)

123
Q

How is data acquired in early units?

A

cross sectional image reconstructed from many line transmission measurements made in different directions

124
Q

What are projection measurements?

A

Early CT radiation detector generates a voltage proportional to radiation intensity which are then sent to an A to D conversion

125
Q

true or false:

all CT generations measure same transmission intensities in many directions

A

true

126
Q

What are improvements of CT?

A

protocol for obtaining many line transmissions

number of line transmissions obtained simultaneously

detector location

overall acquisition speed

127
Q

What are the 1st generation CTs known as?

A

Translate/rotate

128
Q

__________ CT scanners:

-beam collimated to small round spot (at tube and collimator)

-tube/detector translates left to right

-entire assembly rotates 1st to right

-tube detector translates right to left

-180 translations in alternate directions

-1 degree rotational increments between rotations

A

1st generation CT

129
Q

What is the difference between 1st generation and 2nd generation CT scanners?

A

2nd generation scanners allowed 10 degree rotational increments

(reduced scan times of 20 s to 2 min)

130
Q

_____________ CT scanners are characterized by:

wide angle fan beam

rotational motion only (no translation because detectors rotate with the tube)

30 degree beam

many more detectors

A

3rd generation

131
Q

A third generation CT is known as:

A

non spiral CT

132
Q

______ CT scanners:

tube rotates once around patient (table stationary and data for one slice is collected)

table increments one slice thickness

repeat (tube rotates opposite direction)

A

3rd generation CT

133
Q

_______________ is described by:

faster scan times
(less than 10 sec)
(reduced motion artifacts)
(increased throughput)

Increased tube heat capacity needed
(less delay between scans/ patients)

A

3rd generation scanner

134
Q

A __________ has a stationary detector array.

A

4th generation CT scanner

135
Q

_____________ is the:

continuous rotation of gantry with slip ring technology

patient moves slowly but continuously through gantry (no dead time as gantry reverses)

much faster

A

spiral CT (4th generation)

136
Q

In 4th generation CT, Z axis is _______ to page.

A

perpendicular

137
Q

In 3rd generation CT scanner, Z axis is ______ to the page.

A

perpendicular

138
Q

Spiral CT is also known as _____.

A

4th generation CT

139
Q

slice by slice

volume acquisition
(data for entire volume collected)
(patient moves in axial direction during scan)
(tube traces spiral helical path through patient)

describes_______.

A

4th generation CT

140
Q

What are the advantages of spiral CT?

A

volume data acquisition in single breath hold

no delay between slices

improved 3D imaging

improved multi planar image reformatting

special applications
(bone and mineral content)
(radiation treatment planning)
(CT angiography)

141
Q

Multi Slice CT scanners appeared in the ________.

A

2000s

142
Q

multiple rows of fan beam detectors

wider fan beam in axial direction

table moves much faster

substantially greater throughput

describe ______________.

A

multi-slice CT scanners

143
Q

What are the advantages of multi slice CT scanners?

A

scans at much greater speed

allows scanning of same volume with thin slices

makes possible additional clinical applications

144
Q

All recent CT scanner x ray tube and detectors _______.

A

rotate around the patient.

145
Q

_________ measure radiation transmitted through patient for various pencil beam projections.

A

detectors

146
Q

During _____________, relative transmission is calculated from the fraction of the beam exiting the patient.

A

scanning

147
Q

CT detectors are electronic and ____________.

A

quantitative

148
Q

The output of CT detectors are _________ and sent to the computer.

A

digitized

149
Q

What are the three photon phases?

A

nothing

absorption

scatter

150
Q

Are unaffected photons good for the image?

A

Yes; the have the same energy and direction and do not interfere with the CT image

151
Q

In __________ the photon disappears and its energy is absorbed by the material.

A

absorption

152
Q

Why are absorbed photons good?

A

create differential absorption which forms the CT image

153
Q

Why are absorbed photons bad?

A

contribute to patient dose

154
Q

Scatter is due to _______ energy photons.

A

low

155
Q

Scattered photons are bad because they __________ the image.

A

degrade

156
Q

What is attenuation and what are it two forms of photon phates?

A

Anything which removes original photons from the beam

absorption and scatter

157
Q

In mono energy (point source) each cm of material reduces beam intensity by a _______ percentage.

A

fixed

158
Q

I = I o e^-ux are for photons which are ____________.

A

neither absorbed nor scattered

159
Q

I = I o e^-ux is for _________ photon beams.

A

mono energetic

160
Q

In the equation, I = I o e^-ux, the variables mean:

A

I= exiting beam intensity
I0= incident beam intensity
e= constant (2.718)
u= linear attenuation coefficient (property of absorber material and beam energy)
x= absorber thickness

161
Q
A

CT Physics (2 decks)

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