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CMI 360 > Test 1 > Flashcards

Test 1 Flashcards

1
Q

Where is x-rays used in

A

radiography and CT imaging

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2
Q

When is gamma rays used?

A

To image the distribution of radio-pharmaceuticals in nuclear imaging

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3
Q

Where is radio-frequency used in

A

ultrasound and MRI

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4
Q

What is visible light used for?

A

observation and interpretation of images

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5
Q

What is radiation

A

energy that travels through space or matter

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6
Q

How does EM radiation travel?

A

Straight lines at constant speed

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7
Q

EM Radiation
____ mass
unaffected by ______

A

no mass
unaffected by either electrical or magnetic fields

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8
Q

amplitude

A

wave intensity ; maximal height

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9
Q

wavelength

A

distance between any 2 identical points on adjacent cycle

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10
Q

period

A

time required to complete one cycle of a wave

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11
Q

frequency

A

of periods/second
1/period

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12
Q

phase

A

temporal shift of one wave

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13
Q

speed formula

A

c=hv

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14
Q

what is plank’s constant (h)

A

6.62 x 10^-34 J sec

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15
Q

electron volt (eV)

A

energy acquired by an electron as it moves over electrical potential voltage of 1V in a vacuum

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16
Q

1 eV = ____ J

A

1.6021 x 10^-19 J

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17
Q

atomic number (Z) represents

A

of protons in nucleus

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18
Q

mass number (A) represent

A

protons and neutrons in nucleus

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19
Q

How to determine max number of electrons in atom

A

2n^2
n = neutrons

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20
Q

Types of interactions of radiations for a photon

A
  • penetrate matter without interacting
  • all energy gets absorbed by interacting matter
  • scatter or deflected from original direction and loses part of energy to interacting matter
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21
Q

Types interactions of ionizing EM radiation with matter

A

Excitation
Ionization
Delta rays

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22
Q

what type of ionizing interaction has incident photon’s transferred to the electron, raising to a higher shell
A. excitation
B. Ionization
C. delta rays

A

A. excitation

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23
Q

what type of ionizing interaction transfer energy that exceeds the electron binding energy
A. excitation
B. Ionization
C. delta rays

A

B. ionization

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24
Q

List photon matter interactions

A

photoelectric effect
compton scattering
pair production

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25
Q

what type of ionizing interaction has ionized electron that have enough energy to cause further ionizations
A. excitation
B. Ionization
C. delta rays

A

C. delta rays

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26
Q

What is excitation used in? type of beam?

A

mammography
monoenergetic beam

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27
Q

The inherent contrast resolution is defined as the number of ____
a. bits per pixel
b. line pairs per mm (lpmm or lp/mm)

A

bits per pixel

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28
Q

Contrast resolution is ____
a. the ability to distinguish between differences in intensity in an image.
b. the ability to distinguish between object or structures that are close but not actually touching.

A

A

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29
Q

Spatial resolution is ____
a. the ability to distinguish between differences in intensity in an image.
b. the ability to distinguish between object or structures that are close but not actually touching.

A

B

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30
Q

Contrast resolution can also be quantified as _____ (2)

A
  1. % of objects detected in image
  2. # of shades of gray
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31
Q

The spatial resolution is measured in ____
a. bits per pixel
b. line pairs per mm (lpmm or lp/mm)

A

B

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32
Q

_____ resolution is most accurately described as “frequency”
a. spatial
b. contrast

A

A

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33
Q

lower lpmm = ____ resolution

A

lower

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34
Q

Compared to general Xray, CT provides better image contrast through ____

A

highly collimated thin beam that minimize scatters

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35
Q

what are the 4 things CT has to overcome limitation of radiography

A
  1. minimize superimposition
  2. improve contrast
  3. record small contrast difference in tissue density
  4. reconstruction
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36
Q

3 steps of CT physical principles

A

data acquisition –> data processing –> image display –> storage

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37
Q

which steps determine Hounsfield numbers
a. data acquisition
b. data processing
c. image display

A

B

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38
Q

Basic data acquisition scheme is to determine ___

A

attenuation in tissue

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39
Q

what are 2 types of data acquisition

A
  1. slice-by-slice
  2. volume
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40
Q

In data acquisition, what is needed to be calculated for CT reconsturction

A

attenuation

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41
Q

attenuation is the reduction of ____

A

intensity of radiation beam as it pass through object

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42
Q

attenuation is caused by __ (2)

A

absorption and scattering

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43
Q

Attenuation depends on ____ (3)

A
  1. effective atomic density
  2. atomic # of absorber
  3. photon energy
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44
Q

what are 2 types of attenuated beam

A

heterogeneous
homogeneous

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45
Q

which beam has photons with different energies
a. heterogeneous
b.homogeneous

A

A

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46
Q

which of the following characteristic does not apply to homogenous beam
a. photons have same energy
b. monochromatic
c. polychromatic
d. monoenergetic

A

C

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47
Q

unit for linear attenuation coefficient

A

cm^-1

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48
Q

The Beer equation assumes homogeneous beam aka _____ that Hounsfield used for first CT

A

gamma source

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49
Q

During transmission, the energy of ____ beam does not change

A

homogenous

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50
Q

In diagnostic photon energy range, attenuation is caused primarily by _____

A

PE

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51
Q

which of the following beam has linear attenuation coefficient determined by # of photons passing through
a. heterogenous
b.homogeneous

A

A

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52
Q

two step of data processing

A
  1. preprocess raw data from detectors
  2. image reconstruction
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53
Q

CT # are calculated on a basis with attenuation of ____

A

water

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54
Q

CT # = utissue - uwater/u water x K
what does value K stand for

A

contrast factor or scaling factor

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55
Q

K= 500 = CT # = _____
a. EMI Number
b. Hounsfield scale

A

EMI number

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56
Q

K= 10000 = CT # = _____
a. EMI Number
b. Hounsfield scale

A

B

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57
Q

CT # = 1000
a. skull
b. lung
c. cyst
d. lipoma

A

A

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58
Q

CT # = 5
a. skull
b. lung
c. cyst
d. lipoma

A

C

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59
Q

CT # = -600
a. skull
b. lung
c. cyst
d. lipoma

A

B

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60
Q

CT # = -100
a. skull
b. lung
c. cyst
d. lipoma

A

D

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61
Q

in CT, ___ technique is used - why?

A

high
1. reduce dependence of attenuation coefficient on photon energy
2. reduce contrast of bone relative to soft tissue
3. produce high radiation flux at detector
4. ensure optimum detector response

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62
Q

In image display, it establish the correspondence between ___

A

CT # & gray level

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63
Q

Window width control ____

A

contrast

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64
Q

window level control

A

brightness

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65
Q

range of CT # displayed is ____
a. ww
b. wl

A

A

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66
Q

median of range of CT # is ___
a. ww
b. wl

A

B

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67
Q

appearance of image can by changed by ___

A

varying window width and level

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68
Q

scan FOV is ___

A

transmission measurement recorded during scanning

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69
Q

display FOV has to be _____ or equal to scan FOV

A

lesser

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70
Q

pixel size can be computed from ____ & ___

A

FOV
matrix size

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71
Q

each pixel in CT has ___

A

range of gray shades

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72
Q

voxel size depend on ___ (3)

A

FOV
matrix size
slice thickness

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73
Q

1 common limitation of CT & Radiography

A

cant image small differences in tissue contrast

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74
Q

What type of photon matter interaction occurs at 30-150 keV?
A. photoelectric
B. compton scattering
C. pair production

A

A. photoelectric

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75
Q

What energy level does compton scattering occur?
A. 30-150keV
B. 150-30000keV
C. > 30000keV

A

B. 150-30000keV

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76
Q

What energy level does pair production occur?
A. 30-150keV
B. 150-30000keV
C. > 30000keV

A

C. > 30000keV

77
Q

What occurs in photoelectric effect

A

part of energy lost to overcome electron’s binding energy and to remove it from atom
other part of energy is transferred to electron as kinetic energy and deposited near interaction site

78
Q

How is fluorescent radiation produced

A

after effect from photoelectron effect - drop in energy creates characteristic radiation initiated by an incoming photon

79
Q

What is fluorescence

A

energy of photon is used to create a second photon of less energy

80
Q

fluorescent radiation is in form of light or xray depends on _______

A

binding energy levels in absorbing material

81
Q

what is the probability of compton scattering

A

inversely proportional to energy 1/E and almost independent of atomic number Z

82
Q

pair production occurs only when initial photon energy is _____

A

very high

83
Q

pair production occurs near

A

nucleus of atom

84
Q

Once the initial photon interacts with the electron what occurs in pair production

A

the electron and positron pair move in different paths away from each other –> electron-positron pair

85
Q

what is a positron

A

originates in nucleus
has positive charge and mass equal to electron
immediately joins an electron

86
Q

what is a more common photon interaction?

A

photoelectric interaction

87
Q

the composition/type of radiation is dependent on

A

anode material
kV
filtration

88
Q

Disadvantages of analog form for transmission of data

A

signal can be distorted
expensive

89
Q

list 3 examples of signal distortion

A

inaccuracies when signals are amplified
attenuation losses
electronic noise

90
Q

advantages of digital form for transmission of data (4)

A

immune to accumulated errors caused by signal distortion
no amplification of incoming data
error correction with transmission of redundant information
less expensive than analog

91
Q

How is analog converted to digital

A

sampling
digitization/quantization

92
Q

con to analog to digital conversion (ADC)

A

loss of information

93
Q

what is the limitation of sampling

A

sampling below the Nyquist limit aliases

94
Q

what is the limitation of quantization

A

limited to finite number of possible values

95
Q

what is nyquist limit

A

min sampling rate to accurately represent analog signal

96
Q

digital signal can only ______ of analog signal

A

approx the value

97
Q

what is translation

A

movement of xrays through matter –> penetration and interaction

98
Q

what is view

A

plane of acquisition –> coronal, axial, sagittal

99
Q

what is data sample

A

measurement of xray beam intensity after translation across the object

100
Q

what is attenuation

A

reduction of beam intensity as it goes through matter –> by absorption or scatter

101
Q

what is attenuation affect by?

A

beam energy and atomic number of absorber

102
Q

2 characteristics of ADC

A

speed and accuracy

103
Q

if accuracy increases ____

A

longer it takes to digitize image

104
Q

accuracy is depended on ____ (2)

A

sampling and quantization of signal

105
Q

more sampling = _____ quantization levels = _____ accurate

A

more
more

106
Q

to have less errors than the uncertainty what must occur for ADC

A

ADC must sample at sufficiently high rate to give sufficient number of bits

107
Q

in the number system for storage and transfer of data:
the most significant digit is:
the least significant digit is:

A

most: left most digit in number
least: right most digit

108
Q

1101 in binary means

A

13 BITCHES jk just 13

109
Q

who is jasmine quoch

A

a cow

110
Q

2 major factors affect xray production

A

atomic number of target material

KE of incident electron

111
Q

in xray production, the quantity is __
a. exposure
b. spectrum

A

A

112
Q

in xray production, the quality is __
a. exposure
b. spectrum

A

B

113
Q

exposure and spectrum of xray production can be controlled by ____ & ___

A

electrical quantities (kV, mA) + exposure time

114
Q

what are 2 primary anode configurations

A

stationary
rotating

115
Q

____ used for most diagnostic x-ray applications for their
greater heat loading and consequent higher x-ray output capabilities
a. stationary anode
b. rotating anode

A

B

116
Q

factors affect xray emission ___ (3)

A

quality
quantity
intensity

117
Q

_____ determines the efficiency of the
bremsstrahlung output (∝ Z), and also determines
characteristic x-rays.
a. target material
b. applied potential
c. generator waveform

A

A

118
Q

____ determines the maximum energy
of the bremsstrahlung spectrum
a. target material
b. applied potential
c. generator waveform

A

B

119
Q

____ determines the energy spectrum of
the emitted x-rays by determining the average applied
voltage
a. target material
b. applied potential
c. generator waveform

A

C

120
Q

____ is the rate of electron flow from the
cathode to the anode
a. tube current
b. exposure time
c. beam filtration

A

A

121
Q

___ removes low energy photons
a. tube current
b. exposure time
c. beam filtration

A

C

122
Q

what are 4 types of data

A
  1. measurement
  2. raw
  3. convolution
  4. image
123
Q

____ is data direct from the detectors.
1. measurement
2. raw
3. convolution
4. image

A

1

124
Q

___ all the data that
is obtained from the
detectors after it is
preprocessed
1. measurement
2. raw
3. convolution
4. image

A

2

125
Q

____ is the data that is preserved
1. measurement
2. raw
3. convolution
4. image

A

2

126
Q

____ Improves contrast by
suppressing high spatial frequencies (represented
by bone-soft tissue
interfaces).
a. high-pass convolution filters
b. low-pass convolution filters

A

A

127
Q

Improves spatial resolution by suppressing low spatial frequencies (represented by
soft tissue such as brain and
liver tissue).
a. high-pass convolution filters
b. low-pass convolution filters

A

B

128
Q

reconstructed data is also known as ___
1. measurement
2. raw
3. convolution
4. image

A

4

129
Q

scan data is also known as ___
1. measurement
2. raw
3. convolution
4. image

A

2

130
Q

__ is Data that has been
back-projected onto
the image matrix
1. measurement
2. raw
3. convolution
4. image

A

4

131
Q

____ - is continuous images, continuous distribution
of light intensity as a function of position
(eg. black and white photos)
a. analog
b. digital

A

A

132
Q

_____ - numerical representations of objects, ADC converts continuous signal to
discrete signal
a. analog
b. digital

A

B

133
Q

3 steps of image digitization

A

scan –> sample –> quantization

134
Q

___ divide the image into small regions called
pixels, resulting in a matrix characterized
by rows and columns.
a. scan
b. sample
c. quantization

A

A

135
Q

____ process that measure the brightness of each pixel
a. scan
b. sample
c. quantization

A

B

136
Q

__the brightness level of each pixel measured is assigned an integer called a gray level
a. scan
b. sample
c. quantization

A

C

137
Q

____ has the output pixel is
based only on the
input pixel
a. point operator
b. local operator
c. global operator

A

A

138
Q

____ has the output image pixel value is determined from a small area of pixels
around the input pixels
a. point operator
b. local operator
c. global operator

A

B

139
Q

____ has the entire input image is used to compute the value of the pixel in the output image.
a. point operator
b. local operator
c. global operator

A

C

140
Q

___ modify spatial resolution
a. geometric operator
b. local operator
c. global operator

A

A

141
Q

DICOM stands for ___

A

digital imaging and communication in medicine

142
Q

what does bit stand for? what is it used for

A

binary digit
in computer memory and storage

143
Q

how many bits in a byte

A

8

144
Q

how many bits in a word

A

32-64 dependent on system

145
Q

what does ASCII stand for

A

american standard code for information interchange

146
Q

what is ASCII used for

A

represent letters and other non-numeric characters

147
Q

what is DAC used for

A

convert digital signal to analog form

148
Q

if information is lost in ADC can DAC restore?

A

no

149
Q

what is serial transfer of data

A

unit of data transmitted one after another over a single wire

150
Q

what is parallel transfer of data

A

data is transmitted simultaneously over several wires

151
Q

What executes instructions in programs to process data
A. Main memory
B. Data bus
C. Central processing unit (CPU)
D. Input/output (I/O) devices

A

C

152
Q

What stores the program and data
A. Main memory
B. Data bus
C. Central processing unit (CPU)
D. Input/output (I/O) devices

A

A

153
Q

What allows info to be accessed and retrieved from the computer and to be stored
A. Main memory
B. Data bus
C. Central processing unit (CPU)
D. Input/output (I/O) devices

A

D

154
Q

What links CPU, memory, and I/O devices
A. Main memory
B. Data bus
C. Central processing unit (CPU)
D. Input/output (I/O) devices

A

B

155
Q

What is random access memory (RAM)

A

memory that the CPU can both read and write
volatile component

156
Q

what factors affect time for a computer to complete a task (computer processing speed)

A

CPU clock speed
parallel processing
width + clock speed of data bus between CPU and main memory
access times and data transfer rates of mass storage devices

157
Q

what are the 2 computer languages used

A

machine
high-level

158
Q

characteristics of machine language

A

actual binary instructions executed by CPU
requires detailed knowledge of the particular microprocessor chip

159
Q

characteristics of high-level language

A

resemble human language
write program without detailed knowledge of machine arch
include FORTRAN, C/C++, Java etc
requires compiler or interpreter program to translate to binary

160
Q

what is translation?

A

movement of x-rays through matter

161
Q

is the smallest discrete intensity unit of an image

A

pixel

162
Q

a mathematical process that generates 3D images from x-ray data acquired from 2D planes

A

reconstruction

163
Q

what is also known as potential difference?

A

voltage

164
Q

the rate at which electrons flow through a 2D image

A

current

165
Q

a passive electronic device that transfer electric energy from one circuit to another increasing or reducing the voltage via induction?

A

transformer

166
Q

where is induction used?

A

transformers

167
Q

it is the measurement of x-ray beam intensity after translation across the object

A

data sample

168
Q

the area dimensions of the anatomic region being scanned

A

field of view

169
Q

During the production of x-rays the kinetic energy of electrons are converted into what?

A

heat (mostly)
characteristic x-rays (partially)
bremsstrahlung radiation (rare)

170
Q

where does the conversion of kinetic energy into ionizing photons takes palce?

A

anode

AKA electron gun

171
Q

what are the factors that affect x-ray production?

A

atomic number of the target material

kinetic energy of the incident photon

172
Q

what are the 2 types of anodes?

A

rotating and stationary

173
Q

what is the purpose of the generator waveform

A

manipulates electrical current to ensure there is a consistent negative (anode) and positive (cathode) charge

174
Q

what are the factors that control x-ray spectrum

A

tube current (mA)

exposure time (s)

beam filtration

175
Q

what collimator shapes the beam to the area of interest

(CT collimators)

A

prepatient collimator

176
Q

what collimator shapes the beam and reduces scatter
(CT collimators)

A

postpatient (detector) collimator

177
Q

what is the anode heel effect?

A

a loss of intensity on the anode side of the tube and it is caused by attenuation of the x-ray beam by the anode.

178
Q

what allows for half of the ac wave to pass

A

half wave rectified system

179
Q

what flips the second half and outputs as 2 positives halves

A

full wave rectified system

180
Q

what type of filtration involves the thickness of glass or metal of the tube and has a field light mirror in the collimator?

A

inherent

181
Q

this type of filtration involves sheets of metal placed in the beam to attenuate low energy x-ray

also includes shaped filters

A

added

182
Q

when talking about detector characteristics what does the term efficiency refer to?

A

it is the ability to capture, absorb and convert x-rays into electrical signals

183
Q

what do CT detectors need to posses in order to operate at maximum efficiency

A

HIGH

capture efficiency-the fraction of incident photons that interact with the detector

absorption- ability to absorb the energy of the x-ray beam that interacts with the detector

conversion efficiency- ability of the detector to convert x-ray energy into a signal

184
Q

what is stability

A

the steadiness of the detector response

185
Q

what is response time

A

the speed with which the detector can detect an x-ray event and recover to detect another one

186
Q

the ratio of the largest signal to be measured and the smallest

A

dynamic range

187
Q

what formula is used to determine whether or not a detector is optimal?

A

total detector efficiency= capture efficiency x absorption efficiency x conversion efficiency

188
Q

What does ADC stand for and what is its purpose?

A

analog to digital conversion

a device that converts the analog signal to a sequence of numbers having finite precision through the processes of sampling, digitization/ quantization

189
Q

what is ADC characterized by?

A

sampling rate
number of bits of output per sample

CMI 360 (2 decks)

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