Final Exam Review Flashcards
1
Q
What are 2 types of scintillator materials?
A
Cesium Iodine
Gadolinium
2
Q
What does a scintillator do?
A
Converts x-rays to light
3
Q
Cesium Iodine Vs. Gadolinium Oxysulfide
A
CSI- long crystal columns that direct the light down to the TFT, higher spacial resolution due to less light spread
Gd2O2S-random unstructured crystal layer, light can escape laterally before reaching TFT(air pockets)
Lower spacial resolution due to more light spread
Good for rugged applications
4
Q
What is the TFT? And function?
A
Thin film transistor
-isolates each pixel element and acts like a switch to send electrical charge image processor
5
Q
What is fill factor?
A
% of pixel face that is sensitive to x-rays
Approx. 80% leaving 20% of the beam that doesn’t contribute to image
6
Q
Photodetector?
A
- holds the pixels
- made of amorphous silicon
7
Q
CCD?
A
Charged Coupled Device
- photodetector
- electronics embedded into silicon chip
- converts light to electrical charge & stores it
- Charge is released to the ADC (analog to Digital Converter)
8
Q
Advantages of Digital?
A
- wide exposure latitude(can detect lots of grays)
- reduction in repeats
- can compensate for over/under exposure
- environmentally friendly
9
Q
3 components of film?
A
- cassette
- intensifying screen
- film
10
Q
What is the purpose of the intensifying screen?
A
- reduces patient does because it converts x-rays to visible light
- decreases resolution because of light
11
Q
Layers of the intensifying screen (4)
A
- Protective layer
- Phosphor layer
- reflecting layer
- base
12
Q
Function of phosphor layer?
A
-emits light when x-rays hits
13
Q
DQE?
A
Detective Quantum Efficiency
-% of x-rays absorbed by the screen
14
Q
CE?
A
Conversion Efficiency
-amount of light emitted for each x-ray absorbed
-Characteristic of phosphor layer
15
Q
2 types of luminescence?
A
- Fluorescence -light is emitted only while being stimulated
(Light bulb) - Phosphorescence- light emitted even after stimulation
(Glow in the dark sticker)
16
Q
Phosphor factors that effect the image? (4)
A
- Material Composition-calcium tungstate vs. Rare earth
- Thickness of layer- thicker layer=increased DQE
- Concentration-more concentrated = higher screen speed
- Size of Phosphor- larger phosphor = more light produced per x-ray interaction
17
Q
Intensification Factor?
A
exposure without screen/exposure with screen=IF
-gives information about patient dose
18
Q
Screen Speeds ?
A
- describes Efficiency of x-ray conversions to light
- calcium tungstate is used for a basis of comparison with assigned value of 100
19
Q
How does screen speed effect does?
A
higher speed =lower dose
20
Q
How does screen speed effect detail?
A
Higher speed = less detail
21
Q
Uncontrolled speed Factor? (6)
A
- built in
1. Phosphor composition
2. Phosphor thickness
3. Reflective layer (has one or doesn’t)
4. Dye in phosphor layer
5. Crystal Size
6. Crystal concentration
22
Q
How does phosphor size and thickness effect speed?
A
Greater size and thickness = higher speed
23
Q
Controllable speed Factors? (3)
A
- Radiation quality- high KVP =high Intensification Factor
- Processing
- Temperature- higher IF at low temp
24
Q
Film base? Fog?
A
Base- colour added to film base
Fog- any exposure during storage, contamination, processing
25
On a characteristic curve the slope is?
-the degree of contrast
26
Slope of the line is drawn between points corresponding to OD (0.25-2) above base and fog densities
.
27
Gradient on characteristic curve?
-slope of the tangent at any point on the curve
28
Toe gradient?
-more important than average because many clinical OD's appear in this region
29
Shoulder Gradient?
-important in mammo, most of their OD's are in this region
30
Latitude?
Range of exposures that the image receptor can display
- Wider=lower contrast
- Narrow=high contrast q
31
Speed?
The ability of image receptor to respond to an x-ray exposure
-also known as Measure of Sensitivity
32
Changing speeds formula?
RS1/RS2=mAs2/mAs1
33
Image Receptor Speeds effect?
- radiation sensitivity
- density
- dose
34
Quantum Mottle?
- not enough radiation hits the IR
- more light producing the image rather than x-rays
- it will appear splotchy, mottled, and grainy
- decreases image detail
- need to increase mAs to correct it
35
4 Factors that effect radiographic image quality?
1. Photographic
- optical density
- contrast
2. Geometric
- detail
- distortion
36
What is recorded detail?
-degree of sharpness of structural lines on a radiograph
37
Synonyms for Detail?
- recorded detail
- definition
- sharpness
- blur
- resolution
38
What is resolution?
- ability of an imaging system to distinguish between 2 adjacent structures
- expressed in (line pairs/mm)
39
Resolution is the combination of?
- Spacial resolution ( ability to image small objects )
| - Contrast resolution ( ability to distinguish between 2 objects with similar subject contrast )
40
Line pairs consist of?
-lead stripe(line) and air space (space) = line pair
41
How do line pairs effect resolution?
More line pairs = higher resolution
42
Factors that control detail? (3)
- Geometric unsharpness
- Motion unsharpness
- Image receptor unsharpness
43
Factors that effect Geometric Unsharpness?
- focal spot size ( ranges from 0.1-3.0 mm )
| - distance ( SID & OID )
44
What is focal spot blur?
Occurs because the effective focal spot is not a single point
45
The most important factor for spacial resolution is?
- Focal spot blur
| - High contrast objects that are smaller than focal spot blur can't be imaged
46
How does magnification effect blur?
-more magnification = more blur
47
How to decrease focal spot blur?
- use smallest focal spot possible
- largest SID possible
- Smallest OID possible
48
Less focal spot blur on Anode Side
.
49
Why does increasing SID reduce blur?
-diverging rays become more perpendicular to object which decreases the unsharpness
50
How does decreasing OID decrease blur?
-Less room for diverging rays between patient and IR
51
What has the greatest effect of Geometric unsharpness?
-OID
52
The most detrimental effect on recorded detail is?
- motion unsharpness
| - motion of anatomy, tube, or image receptor
53
2 Types of patient motion?
- Voluntary
| - Involuntary
54
What is image receptor unsharpness affected by?
The device used to record the image
- do to manufacture
- don't have control over this
55
If you____________speed, you _______________unsharpness
Increase, Increase
56
Factors that affect recorded detail? (4)
- Phosphor size
- Phosphor layer thickness
- Phosphor Concentration
- Film Screen Contact
57
__________phosphor size results in a _____________recorded detail
Large, Decrease
58
Factors that affect resolution of digital imaging systems(2)
- Geometric properties of the IR
| - Image Processing system
59
Factors that limit detail? (4)
- Phosphor size
- Layer thickness
- Concentration
- Scanning of the screen and processing
60
_________the pixel, ___________the resolution
Smaller, Higher
61
Fill Factor?
- area of detector that is light sensitive
- HIGH fill factor=HIGH resolution
- more transitions(steps)=REDUCES recorded detail
62
Distortion? Types?
- results from radiographic misinterpretation of an object
1. Size distortion-magnification
2. Shape distortion-elongation and foreshortening
63
Ways to minimize distortion?`
- distances
- central ray
- patient postition
- IR position
64
Size Distortion?
And increase in the size of an objects image compared to its actual size
-Due to OID (greatest effect)
65
Magnification Factor Formula
MF=SID/SOD (SOD=SID-OID)
OF
MF=Image Size/Object Size
66
Shape Distortion?
- misrepresentation of an object with distortion of its shape
1. Elongation-image appears longer than actual object
2. Foreshortening- image appears shorter than actual object
67
What causes Shape distortion?
- inaccurate central ray alignment of tube
- inaccurate alignment of part
- inaccurate alignment of IR
68
__________magnification=__________OID
More, More
69
What is Digital Imaging?
-Any imaging acquisition process that produces an electronic image that can be viewed and manipulated on a computer
70
Components of a Computer?
- Input devices
- Output devices
- Processing devices
71
Input Device Examples?
- keyboards
- Mice
- Microphones
- Barcode Readers
- Touch Screens
- Image Scannerss
72
Output Device Examples?
- Monitors
- Printers (paper, laser film)
- Speakers
73
2 Monitor Types?
CRT-Cathode Ray Tube
LCD-Liquid Crystal Display
74
CRT
- Refresh rate
- Controls "flicker" seen by user
- Higher refresh rate=less flicker
75
LCD
Response rate-amount of time for crystal to go from off state to on
-Slower response time=causes blurring
76
Aspect Ratio?
-Ratio of the width of the monitor to the height of the monitor
77
How does CRT work?
- Works like an X-ray tube
- Electrons strike phosphors causing glass to emit a color determined by the intensity of the interaction and area with which electrons interacted
- Electron beam starts in upper left corner and scans across glass side to side
- After reaching bottom it starts again at the top
78
How does LCD work?
- Images are produced by shining or reflecting light through a layer of liquid crystal and a series of color filters
- Light passes through the first layer, and when a current is applied to the crystal layer it aligns and allows light in carrying intensities through to the next layer
79
Different types of Workstations?
-Administration
-Tech
-PACS
-CR reader
-Radiologist
_Archives
80
What is a Digital Image?
- one that has been converted into numerical values for transmission or processing
- Requires DR or CR
81
What is an Array Processor?
- Special computer that functions as a peripheral device
| - Uses its own memory to preform simultaneous math operation at very high speeds
82
What factors remain unchanged in Digital Imaging?
- Patient positioning
- Projections
- Collimation
83
Pros of Digital?
- wider range of exposure
- linear response
- greater range of densities
- easily manipulated with computer
- post processing
84
What are the critical characteristics of a digital image?
- Spatial resolution
- Contrast resolution
- Noise
- Dose efficiency
85
Pixel? Size? Depth?
- smallest element in digital imaging
| - Size of pixel is DIRECTLY related to the amount of spacial resolution/detail of image
86
_____________pixel size=__________detail
Smaller, Increases
87
___________bit depth=____________grey levels displayed
Higher, More
88
Matrix?
- image is recorded as a matrix
- numerical values
- divided into small boxes
- Each pixel displays numerical value and a density level proportional to degree of the incoming signal
89
__________matrix size=_____________resolution
___________the matrix=_____________the pixels
Increased, Increased
Larger, Smaller
90
What is Dynamic Range?
- The ability to respond to varying levels of exposure
| - identified by the bit capacity of each pixel
91
What is windowing?
- Allows us to see only a portion of the entire dynamic range
- Raw data image will show full dynamic range
- Appears very low contrast, as so many shades of grey are displayed
92
What is Window Level?
____________Window Level=___________Brightness
- Controls the image brightness ( controlled by varying the value of each pixel)
- DIRECT relationship
-Decreased, Increased
93
Increasing brightness of the image.....
Decreasing brightness of the image.....
- All pixels are raised to higher value by the same factor
| - All pixels are decreased to lower value by the same factor
94
What is Window Width?
________Window Width=___________Contrast
- Controls image CONTRAST
- INVERSE RELATIONSHIP
Decreased, Increased
95
A NARROW window width=
A WIDE window width=
Decreased window width=Increased Contrast
Increased window width=Decreased Contrast
96
What does Image Sampling determine?
Image LOCATION and SIZE of the signal
97
What is a Histogram?
Graphical representation of the optimal densities within the collimated area
- Takes the image data from sample
- System finds useful signal by locating the minimum and maximum signal within the regions of interest on the image
- all intensities are plotted on the histogram
98
The values at the ______ of the histogram represent ______
The values at the ______ of the histogram represent______
The values at the ______of the histogram represent______
Left, Black
Right, White
Middle, Medium tones
99
How will a dark image appear on a histogram? A light image?
- Most data points will be on the LEFT
| - Most data points will be on the RIGHT
100
NyQuist Theorum states?
When sampling a signal the sampling frequency must be greater than TWICE the frequency of the input signal so that the reconstruction of the original image will be as accurate as possible
101
What is Aliasing?
-Produces an image that looks like two superimposed images just slightly misaligned
102
What is Automatic Rescaling?
- used for high and low exposures
- attempts to correct pixel display
- it produces images with uniform density and contrast regardless of the exposure
103
What will occur if the exposure is too small?
-Quantum mottle
104
What will occur if the exposure if too large?
Loss of contrast and edge sharpness and increased scatter
105
What is a LUT?
- Look up table
| - used as a reference to evaluate the raw info and correct pixel values during processing
106
Can the raw data be changed?
NEVER!
107
When the slope of the graph is changed what will be increased/decreased?
-contrast
108
When moving the line along the y-axis what will be increased/decreased?
-Brightness/density
109
___________slope=____________contrast
____________slope=_____________contrast
Greater, High
Less,Low
110
What is an exposure indicator?
-refers to the amount of exposure received by the IR
111
Factors that affect EI #'s
- Technical factors
- Histogram analysis error
- Patient positioning
- Image processing algorithms
- SID
- Collimation
- Beam entering
- Artifacts
112
Following and exposure what happens?
1. The IR is read and a histogram in formed
2. EI #'s represent the average gray shade value of the image
* *based on collimated boundaries**
3. Compared to a pre-programmed histogram of the same body part
113
EI_s #'s Linear Response
-As exposure increases the EI_s increases
114
EI # Direct Response
Carestream/Kodak
Philips Digital
Double the exposure=EI increases by 300
Halve the exposure=EI decreases by 300
Double the exposure=Halve the EI number
115
SNR (Signal to noise ratio) components
1. Signal-meaningful pattern carrying info about subject
2. Noise-Chaotic pattern, carrying no info about subject
- Quantum noise=quantum mottle
- Electronic noise=created during amplification of the signal
116
_________SNR=_________is HIGHER than __________
_________SNR=_________is LOWER than ___________
High, signal, noise
Low, signal, noise
117
Shuttering/masking?
-Used to black out the white collimation borders eliminating glare
118
Image Orientation?
-Allows us to rotate images
119
Image Annotation?
-Allows additional info to be added to image
120
2 Types of Magnification?
1. Magnifying glass function-only one part of the image is being magnified
2. Zoom function-the whole image is getting bigger
121
Spacial Frequency Filtering ?
After signal is obtained for each pixel, to shorten process time and minimize storage the signals are averaged
-MORE pixels involved=SMOOTHER image
122
What is High Pass Filtering? Low pass?
- When frequencies are amplified
- sharpening effect
- increases contrast and edge effect
- When frequencies are suppressed
- Smoothing
- Can lose small details, reduces noise and contrast
123
Image stitching?
-Multiple images are stitched together to create on big image.
124
4 main types of artifacts?
1. Imaging plate artifacts
2. Plate reader artifacts
3. Image processing artifacts
4. Printer artifacts
125
What are imaging plate artifacts?
- Usually due to aging or wear
| - Plate becomes more prone to cracks due to constant removal and replacement within reader
126
Static Artifacts? Backscatter?
- Causes things to stick inside the IP
| - Worn down or cracked areas of the lead coating on the cassette allow scatter to reach IP
127
What are Image Processing Artifacts?
-Can occur from incorrect part selection or incorrect sampling
128
What are Plate Reader Artifacts?
- Any extraneous line patterns that appear randomly can be caused by issues with electronics
- If IP is not completely erased residual info can be left before next exposure is taken
129
What are Printer Artifacts?
-Fine white lines may appear on the image due to debris in the laser printer
130
What are some examples of operator errors?
- Collimation
- Cassette Orientation
- Technical Factor Selection
131
What is image lag?
-when an image is taken before the detector has finished releasing all the signal for the previous image
Caused by : taking images in rapid succession, over exposure, areas with little beam attenuation
132
A group of two or more computers linked together is a.....
Network
133
LAN?
Local Area Network
| -linked computers that are close together
134
WAN?
Wide area Network
| -Computers that are further apart and must be connected by telephone lines, cables, or radio waves
135
Peer-to-Peer Network
Each party has the same capability and any party can initiate communication
136
Client-Server Based Network
```
Centralized Computer(server) controls operations, files and sometimes computer programs that are attached to the network.
Server-computer that facilitates communication between and delivers info to other computers
```
137
Network Components
- Server
- Think Client
- Thick Client
1. Manages resources for other computers, servers and networked devices
2. Any device that requires a server to complete its tasks
3. Computer that can work independently of the network
138
4 Common Topology's?
1. Star
2. Bus
3. Ring
4. Mesh
139
What is Bus topology?
- All devices physically attached to and listen for communication on a SINGLE wire
- if wire breaks the whole thing stops
140
What is Ring Topology?
Devices are connected in a circle, data travels in one direction until it reaches the correct receiver
141
What is Star topology?
Devices connected to a central hub or switch
-Like a mailbox, anyone can grab anything whenever
142
What is Mesh Topology?
Multiple pathways to connect devices and networks
143
What is DICOM?
- consists of 20 parts
| - standard that makes the images viewable everywhere
144
What is HIS?
-HOlds patient's full medical info
145
What is RIS?
-Holds all radiology specific patient data
146
What is EMR?
- Electronic Medical Record
| - all info
147
3 Fundamentals of PACS?
Image Acquisition
Display Workstations
Archiving
148
What is Image Acquisition?
-Images are acquired in a digital format
149
Review the 4 types of workstations
1. Review
2. Tech
3. Radiologist
4. Image Management
150
Review Workstation
- any computer used to view digital image
| - minor manipulation
151
Radiologist Workstation
- used to make primary diagnosis
| - highest quality
152
Tech Workstation
- review image before sending
| - minor adjustments
153
Image Management Workstation
-used to look up exams or print copies
154
What are the common 4 functions of workstations
1. Navigation-moving through image
2. Image Manipulation-post processing stuff
3. Image Management-can make changes
4. Advanced-Multi-planar Reconstruction, Max and Min Intensity Projection, Volume Rendering Technique, Shade Surface Display
155
PACS Archiving?
-file room for all DICOM images
156
Image Manager?
- Contains the master database of everything in the archive
| - receipt retrieval and distribution
157
Image Storage?
-Actual physical storage device of the archive system
158
What is RAID?
- Redundant array of independent discs
| - Made of several magnetic discs or hard drives linked as an array
159
Examples of Long term storage?
- Optical Disk
- Tape
- Magnetic Disk
