Test 1 Flashcards
1
Q
Where is x-rays used in
A
radiography and CT imaging
2
Q
When is gamma rays used?
A
To image the distribution of radio-pharmaceuticals in nuclear imaging
3
Q
Where is radio-frequency used in
A
ultrasound and MRI
4
Q
What is visible light used for?
A
observation and interpretation of images
5
Q
What is radiation
A
energy that travels through space or matter
6
Q
How does EM radiation travel?
A
Straight lines at constant speed
7
Q
EM Radiation
____ mass
unaffected by ______
A
no mass
unaffected by either electrical or magnetic fields
8
Q
amplitude
A
wave intensity ; maximal height
9
Q
wavelength
A
distance between any 2 identical points on adjacent cycle
10
Q
period
A
time required to complete one cycle of a wave
11
Q
frequency
A
of periods/second
1/period
12
Q
phase
A
temporal shift of one wave
13
Q
speed formula
A
c=hv
14
Q
what is plank’s constant (h)
A
6.62 x 10^-34 J sec
15
Q
electron volt (eV)
A
energy acquired by an electron as it moves over electrical potential voltage of 1V in a vacuum
16
Q
1 eV = ____ J
A
1.6021 x 10^-19 J
17
Q
atomic number (Z) represents
A
of protons in nucleus
18
Q
mass number (A) represent
A
protons and neutrons in nucleus
19
Q
How to determine max number of electrons in atom
A
2n^2
n = neutrons
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
21
Q
Types interactions of ionizing EM radiation with matter
A
Excitation
Ionization
Delta rays
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
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
24
Q
List photon matter interactions
A
photoelectric effect
compton scattering
pair production
25
what type of ionizing interaction has ionized electron that have enough energy to cause further ionizations
A. excitation
B. Ionization
C. delta rays
C. delta rays
26
What is excitation used in? type of beam?
mammography
monoenergetic beam
27
The inherent contrast resolution is defined as the number of ____
a. bits per pixel
b. line pairs per mm (lpmm or lp/mm)
bits per pixel
28
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
29
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.
B
30
Contrast resolution can also be quantified as _____ (2)
1. % of objects detected in image
2. # of shades of gray
31
The spatial resolution is measured in ____
a. bits per pixel
b. line pairs per mm (lpmm or lp/mm)
B
32
_____ resolution is most accurately described as "frequency"
a. spatial
b. contrast
A
33
lower lpmm = ____ resolution
lower
34
Compared to general Xray, CT provides better image contrast through ____
highly collimated thin beam that minimize scatters
35
what are the 4 things CT has to overcome limitation of radiography
1. minimize superimposition
2. improve contrast
3. record small contrast difference in tissue density
4. reconstruction
36
3 steps of CT physical principles
data acquisition --> data processing --> image display --> storage
37
which steps determine Hounsfield numbers
a. data acquisition
b. data processing
c. image display
B
38
Basic data acquisition scheme is to determine ___
attenuation in tissue
39
what are 2 types of data acquisition
1. slice-by-slice
2. volume
40
In data acquisition, what is needed to be calculated for CT reconsturction
attenuation
41
attenuation is the reduction of ____
intensity of radiation beam as it pass through object
42
attenuation is caused by __ (2)
absorption and scattering
43
Attenuation depends on ____ (3)
1. effective atomic density
2. atomic # of absorber
3. photon energy
44
what are 2 types of attenuated beam
heterogeneous
homogeneous
45
which beam has photons with different energies
a. heterogeneous
b.homogeneous
A
46
which of the following characteristic does not apply to homogenous beam
a. photons have same energy
b. monochromatic
c. polychromatic
d. monoenergetic
C
47
unit for linear attenuation coefficient
cm^-1
48
The Beer equation assumes homogeneous beam aka _____ that Hounsfield used for first CT
gamma source
49
During transmission, the energy of ____ beam does not change
homogenous
50
In diagnostic photon energy range, attenuation is caused primarily by _____
PE
51
which of the following beam has linear attenuation coefficient determined by # of photons passing through
a. heterogenous
b.homogeneous
A
52
two step of data processing
1. preprocess raw data from detectors
2. image reconstruction
53
CT # are calculated on a basis with attenuation of ____
water
54
CT # = utissue - uwater/u water x K
what does value K stand for
contrast factor or scaling factor
55
K= 500 = CT # = _____
a. EMI Number
b. Hounsfield scale
EMI number
56
K= 10000 = CT # = _____
a. EMI Number
b. Hounsfield scale
B
57
CT # = 1000
a. skull
b. lung
c. cyst
d. lipoma
A
58
CT # = 5
a. skull
b. lung
c. cyst
d. lipoma
C
59
CT # = -600
a. skull
b. lung
c. cyst
d. lipoma
B
60
CT # = -100
a. skull
b. lung
c. cyst
d. lipoma
D
61
in CT, ___ technique is used - why?
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
62
In image display, it establish the correspondence between ___
CT # & gray level
63
Window width control ____
contrast
64
window level control
brightness
65
range of CT # displayed is ____
a. ww
b. wl
A
66
median of range of CT # is ___
a. ww
b. wl
B
67
appearance of image can by changed by ___
varying window width and level
68
scan FOV is ___
transmission measurement recorded during scanning
69
display FOV has to be _____ or equal to scan FOV
lesser
70
pixel size can be computed from ____ & ___
FOV
matrix size
71
each pixel in CT has ___
range of gray shades
72
voxel size depend on ___ (3)
FOV
matrix size
slice thickness
73
1 common limitation of CT & Radiography
cant image small differences in tissue contrast
74
What type of photon matter interaction occurs at 30-150 keV?
A. photoelectric
B. compton scattering
C. pair production
A. photoelectric
75
What energy level does compton scattering occur?
A. 30-150keV
B. 150-30000keV
C. > 30000keV
B. 150-30000keV
76
What energy level does pair production occur?
A. 30-150keV
B. 150-30000keV
C. > 30000keV
C. > 30000keV
77
What occurs in photoelectric effect
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
How is fluorescent radiation produced
after effect from photoelectron effect - drop in energy creates characteristic radiation initiated by an incoming photon
79
What is fluorescence
energy of photon is used to create a second photon of less energy
80
fluorescent radiation is in form of light or xray depends on _______
binding energy levels in absorbing material
81
what is the probability of compton scattering
inversely proportional to energy 1/E and almost independent of atomic number Z
82
pair production occurs only when initial photon energy is _____
very high
83
pair production occurs near
nucleus of atom
84
Once the initial photon interacts with the electron what occurs in pair production
the electron and positron pair move in different paths away from each other --> electron-positron pair
85
what is a positron
originates in nucleus
has positive charge and mass equal to electron
immediately joins an electron
86
what is a more common photon interaction?
photoelectric interaction
87
the composition/type of radiation is dependent on
anode material
kV
filtration
88
Disadvantages of analog form for transmission of data
signal can be distorted
expensive
89
list 3 examples of signal distortion
inaccuracies when signals are amplified
attenuation losses
electronic noise
90
advantages of digital form for transmission of data (4)
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
How is analog converted to digital
sampling
digitization/quantization
92
con to analog to digital conversion (ADC)
loss of information
93
what is the limitation of sampling
sampling below the Nyquist limit aliases
94
what is the limitation of quantization
limited to finite number of possible values
95
what is nyquist limit
min sampling rate to accurately represent analog signal
96
digital signal can only ______ of analog signal
approx the value
97
what is translation
movement of xrays through matter --> penetration and interaction
98
what is view
plane of acquisition --> coronal, axial, sagittal
99
what is data sample
measurement of xray beam intensity after translation across the object
100
what is attenuation
reduction of beam intensity as it goes through matter --> by absorption or scatter
101
what is attenuation affect by?
beam energy and atomic number of absorber
102
2 characteristics of ADC
speed and accuracy
103
if accuracy increases ____
longer it takes to digitize image
104
accuracy is depended on ____ (2)
sampling and quantization of signal
105
more sampling = _____ quantization levels = _____ accurate
more
more
106
to have less errors than the uncertainty what must occur for ADC
ADC must sample at sufficiently high rate to give sufficient number of bits
107
in the number system for storage and transfer of data:
the most significant digit is:
the least significant digit is:
most: left most digit in number
least: right most digit
108
1101 in binary means
13 BITCHES jk just 13
109
who is jasmine quoch
a cow
110
2 major factors affect xray production
atomic number of target material
KE of incident electron
111
in xray production, the quantity is __
a. exposure
b. spectrum
A
112
in xray production, the quality is __
a. exposure
b. spectrum
B
113
exposure and spectrum of xray production can be controlled by ____ & ___
electrical quantities (kV, mA) + exposure time
114
what are 2 primary anode configurations
stationary
rotating
115
____ 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
B
116
factors affect xray emission ___ (3)
quality
quantity
intensity
117
_____ determines the efficiency of the
bremsstrahlung output (∝ Z), and also determines
characteristic x-rays.
a. target material
b. applied potential
c. generator waveform
A
118
____ determines the maximum energy
of the bremsstrahlung spectrum
a. target material
b. applied potential
c. generator waveform
B
119
____ determines the energy spectrum of
the emitted x-rays by determining the average applied
voltage
a. target material
b. applied potential
c. generator waveform
C
120
____ is the rate of electron flow from the
cathode to the anode
a. tube current
b. exposure time
c. beam filtration
A
121
___ removes low energy photons
a. tube current
b. exposure time
c. beam filtration
C
122
what are 4 types of data
1. measurement
2. raw
3. convolution
4. image
123
____ is data direct from the detectors.
1. measurement
2. raw
3. convolution
4. image
1
124
___ all the data that
is obtained from the
detectors after it is
preprocessed
1. measurement
2. raw
3. convolution
4. image
2
125
____ is the data that is preserved
1. measurement
2. raw
3. convolution
4. image
2
126
____ Improves contrast by
suppressing high spatial frequencies (represented
by bone-soft tissue
interfaces).
a. high-pass convolution filters
b. low-pass convolution filters
A
127
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
B
128
reconstructed data is also known as ___
1. measurement
2. raw
3. convolution
4. image
4
129
scan data is also known as ___
1. measurement
2. raw
3. convolution
4. image
2
130
__ is Data that has been
back-projected onto
the image matrix
1. measurement
2. raw
3. convolution
4. image
4
131
____ - is continuous images, continuous distribution
of light intensity as a function of position
(eg. black and white photos)
a. analog
b. digital
A
132
_____ - numerical representations of objects, ADC converts continuous signal to
discrete signal
a. analog
b. digital
B
133
3 steps of image digitization
scan --> sample --> quantization
134
___ divide the image into small regions called
pixels, resulting in a matrix characterized
by rows and columns.
a. scan
b. sample
c. quantization
A
135
____ process that measure the brightness of each pixel
a. scan
b. sample
c. quantization
B
136
__the brightness level of each pixel measured is assigned an integer called a gray level
a. scan
b. sample
c. quantization
C
137
____ has the output pixel is
based only on the
input pixel
a. point operator
b. local operator
c. global operator
A
138
____ 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
B
139
____ 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
C
140
___ modify spatial resolution
a. geometric operator
b. local operator
c. global operator
A
141
DICOM stands for ___
digital imaging and communication in medicine
142
what does bit stand for? what is it used for
binary digit
in computer memory and storage
143
how many bits in a byte
8
144
how many bits in a word
32-64 dependent on system
145
what does ASCII stand for
american standard code for information interchange
146
what is ASCII used for
represent letters and other non-numeric characters
147
what is DAC used for
convert digital signal to analog form
148
if information is lost in ADC can DAC restore?
no
149
what is serial transfer of data
unit of data transmitted one after another over a single wire
150
what is parallel transfer of data
data is transmitted simultaneously over several wires
151
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
C
152
What stores the program and data
A. Main memory
B. Data bus
C. Central processing unit (CPU)
D. Input/output (I/O) devices
A
153
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
D
154
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
B
155
What is random access memory (RAM)
memory that the CPU can both read and write
volatile component
156
what factors affect time for a computer to complete a task (computer processing speed)
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
what are the 2 computer languages used
machine
high-level
158
characteristics of machine language
actual binary instructions executed by CPU
requires detailed knowledge of the particular microprocessor chip
159
characteristics of high-level language
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
what is translation?
movement of x-rays through matter
161
is the smallest discrete intensity unit of an image
pixel
162
a mathematical process that generates 3D images from x-ray data acquired from 2D planes
reconstruction
163
what is also known as potential difference?
voltage
164
the rate at which electrons flow through a 2D image
current
165
a passive electronic device that transfer electric energy from one circuit to another increasing or reducing the voltage via induction?
transformer
166
where is induction used?
transformers
167
it is the measurement of x-ray beam intensity after translation across the object
data sample
168
the area dimensions of the anatomic region being scanned
field of view
169
During the production of x-rays the kinetic energy of electrons are converted into what?
heat (mostly)
characteristic x-rays (partially)
bremsstrahlung radiation (rare)
170
where does the conversion of kinetic energy into ionizing photons takes palce?
anode
AKA electron gun
171
what are the factors that affect x-ray production?
atomic number of the target material
kinetic energy of the incident photon
172
what are the 2 types of anodes?
rotating and stationary
173
what is the purpose of the generator waveform
manipulates electrical current to ensure there is a consistent negative (anode) and positive (cathode) charge
174
what are the factors that control x-ray spectrum
tube current (mA)
exposure time (s)
beam filtration
175
what collimator shapes the beam to the area of interest
(CT collimators)
prepatient collimator
176
what collimator shapes the beam and reduces scatter
(CT collimators)
postpatient (detector) collimator
177
what is the anode heel effect?
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
what allows for half of the ac wave to pass
half wave rectified system
179
what flips the second half and outputs as 2 positives halves
full wave rectified system
180
what type of filtration involves the thickness of glass or metal of the tube and has a field light mirror in the collimator?
inherent
181
this type of filtration involves sheets of metal placed in the beam to attenuate low energy x-ray
also includes shaped filters
added
182
when talking about detector characteristics what does the term efficiency refer to?
it is the ability to capture, absorb and convert x-rays into electrical signals
183
what do CT detectors need to posses in order to operate at maximum efficiency
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
what is stability
the steadiness of the detector response
185
what is response time
the speed with which the detector can detect an x-ray event and recover to detect another one
186
the ratio of the largest signal to be measured and the smallest
dynamic range
187
what formula is used to determine whether or not a detector is optimal?
total detector efficiency= capture efficiency x absorption efficiency x conversion efficiency
188
What does ADC stand for and what is its purpose?
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
what is ADC characterized by?
sampling rate
number of bits of output per sample
