1
Q
What is the optimal deviation index value?
A
0
2
Q
What deviation index value suggests gross overexposure?
A
> 6.0
3
Q
What deviation index value suggests gross underexposure?
A
< -6.0
4
Q
What is a computer?
A
A programmable electronic device that can store, retrieve, and process data.
5
Q
What are the three main components of a computer system?
A
Input, output, and processing devices.
6
Q
Examples of computer input
A
Keyboards, mice, microphones, bar code readers, touch screens, image scanners
7
Q
Examples of computer output
A
Monitors, printers, speakers
8
Q
Example of computer processors
A
CPU (central processing unit)
9
Q
What is binary code?
A
The machine language of 1s and 0s that computers use to process data.
10
Q
How does a transistor represent binary code?
A
Closed circuit (current passes) = 1
Open circuit (no current) = 0
11
Q
What is a bit?
A
A single unit of data, either 1 or 0.
12
Q
What is a byte?
A
A group of 8 bits; enough memory to store one alphanumeric character.
13
Q
What are common units of computer memory?
A
Kilobytes, megabytes, gigabytes, and terabytes.
14
Q
What are the two main types of computer configurations?
A
Desktop model: horizontal box usually placed on the desk below the monitor.
Tower model: vertical box usually placed under the desk within arm’s reach.
15
Q
What is the motherboard?
A
The largest circuitry board in the computer that houses essential components.
16
Q
What key components are found on the motherboard?
A
CPU, CMOS, BIOS, Bus, Ports, and Memory.
17
Q
What is the CPU?
A
The microprocessor or ‘brain’ of the computer; it processes data and executes instructions.
18
Q
What are the basic tasks of the CPU?
A
Read data from storage, manipulate data, and return it to storage or output devices.
19
Q
How are CPUs identified?
A
By the manufacturer and the speed (clock rate) at which data is processed.
20
Q
What is the BIOS?
A
A set of simple instructions used by the computer during startup.
21
Q
What are the functions of the BIOS?
A
Runs system startup diagnostics, Oversees basic functions, Acts as a bridge between the operating system and hardware.
22
Q
What is the bus?
A
A series of connections and chips that form the computer’s information highway, linking the CPU, memory, and peripherals.
23
Q
What is RAM?
A
Random-Access Memory; temporary storage for data being processed by the CPU.
24
Q
What is the function of RAM?
A
To store information currently being used, allowing the CPU to perform active tasks efficiently.
25
What are ports?
Connectors on the PC that link to external devices like printers, drives, and keyboards.
26
What port is a common connection for most modern devices?
USB (Universal serial bus) port
27
What does CMOS stand for?
Complementary Metal Oxide Semiconductor
28
What is CMOS?
A memory chip that retains hardware information when the computer is off, using a small battery.
29
What else does CMOS do?
Houses the system clock (tracks date/time), Determines CPU speed (using a quartz crystal), Detects hardware changes at startup.
30
What is the function of the power supply?
Converts AC power from the wall into DC voltages for computer components.
31
How much power do most supplies provide?
Between 150W and 400W.
32
What additional features does the power supply have?
A fan for cooling and surge protection to prevent damage.
33
What is the hard drive?
The main storage device for programs and files, using magnetic platters to store data.
34
How do hard drives work?
Disks spin at high speed, and a read/write head accesses or records data on them.
35
What is a CD?
A compact disk made of plastic that holds up to 780 MB of data or 74 minutes of music.
36
What is a DVD?
A disk that can store up to 7 times more data than a CD by using multiple layers.
37
How is data written on DVDs/disks?
Information is burned from the center outward in a spiral pattern; double-sided DVDs can be written on both sides.
38
What are the main types of monitors?
CRT, LCD, Plasma, and OLED.
39
What is aspect ratio?
The width-to-height ratio of the display.
40
What is the aspect ratio of a CRT (cathode ray tube) monitor?
4:3.
41
What is the aspect ratio of a LCD (liquid crystal display) monitor?
16:9.
42
How is monitor size measured?
Diagonally from one corner to the opposite corner.
43
What is an operating system (OS)?
Software that manages hardware and acts as a bridge between applications and hardware.
44
What are common types of operating systems?
Windows, Macintosh, UNIX/Linux.
45
What are factors to consider when choosing computers for radiology use?
Comfort, Cost, Quality, and Purpose.
46
Why might different roles require different computer setups?
For example, radiologists need high-resolution, large, bright monitors for diagnostic images, while clerical staff need only basic monitors.
47
What are the three main computer functions?
Store, retrieve, and process data.
48
What determines a monitor’s display quality?
Resolution, dot pitch, refresh rate, response rate, aspect ratio, and viewable area.
49
What are the three main elements of a digital radiography (DR) system?
Capture Element, Coupling Element, Collection Element
50
What is the capture element?
How the x-ray is absorbed
51
What is the coupling element?
How the x-ray–generated signal is transferred to the collection element (converted into a form of energy light light)
52
What is the collection element?
The device that reads out the signal for processing; may be a photodiode, charge-coupled device (CCD), or thin-film transistor (TFT).
53
Who developed scanned projection radiography (SPR) and for what purpose?
It was developed by CT vendors to help with patient positioning for imaging volumes.
54
Is scanned projection radiography still in use?
Yes, it remains in use in most modern multi-slice helical CT imaging systems.
55
What was one limitation of scanned projection radiography?
The scanning motion took several seconds, which could cause motion blur.
56
What material is used in computed radiography (CR) imaging plates?
Barium fluorohalide crystals contained within the imaging plate (photostimulable phosphor plate or PSP).
57
How does the CR image plate store data?
The remnant x-ray beam interacts with electrons in the barium fluorohalide crystals.
58
How do we read what is on the CR image plate?
The cassette is fed into a reader that scans the plate with a laser, releasing stored electrons. The emitted light is converted into an electrical signal. This signal is digitized to represent image brightness at each matrix location.
59
What happens to the plate after image reading?
Most electrons return to a lower energy state, removing the image from the plate.
60
How is the imaging plate erased?
By flooding it with light to remove any remaining trapped electrons.
61
How sensitive are CR imaging plates?
Extremely sensitive to scatter radiation.
62
What does CR and DR stand for?
CR: Computed Radiography
DR: Direct Readout
Both are digital radiography!
63
How does DR differ from CR?
DR combines image capture and readout in one system; CR requires a separate reader.
64
What components are integrated in a DR flat-panel detector?
Signal storage, signal readout, and digitizing electronics.
65
What are the two main types of DR conversion methods?
Indirect and direct conversion.
66
What is the difference between indirect and direct conversion in DR?
Indirect uses a scintillator (e.g., cesium iodide) to convert x-rays to light, which is then converted to electrical charges. Direct uses amorphous selenium to directly convert x-rays into electrical charges.
67
What happens after x-rays are converted to numerical data?
The digital image can be electronically processed, manipulated, transmitted, or stored.
68
What does CCD stand for?
Charge-coupled device
69
What is a CCD?
A photosensitive receptor and electronic system built into a silicon chip that acts as a coupling device (like a camera).
70
What are the advantages of CCDs?
High sensitivity (detects low levels of light), Wide dynamic range (responds to a wide range of light intensities), Small size (approximately 1–2 cm).
71
What is CsI/CCD imaging?
An indirect DR process where cesium iodide converts x-rays into light, and the CCD converts that light into an electrical signal.
72
What are the benefits of CsI/CCD systems?
High x-ray capture efficiency and good spatial resolution (up to 5 lp/mm).
73
What is GdOS/a-Si imaging?
A DR indirect process where gadolinium oxysulfide (GdOS) acts as the scintillator and amorphous silicon collects the signal.
74
How does GdOS thickness affect image quality?
Thicker GdOS increases speed (sensitivity) but reduces spatial resolution in screen-film radiography. In DR systems, increasing GdOS thickness increases speed without compromising spatial resolution.
75
What does CMOS stand for?
Complementary metal oxide semiconductor
76
What is a CMOS detector?
A type of image sensor that converts light into electrons stored in capacitors within each pixel.
77
What are key features of CMOS detectors?
Low power use, Inexpensive to manufacture, Lower quality and resolution compared to CCDs
78
How does CMOS imaging work?
X-rays are converted into light by a scintillator. The light is stored in capacitors within each pixel.
79
What does each pixel have in CMOS imaging?
Each pixel has its own amplifier, which switches on and off to convert light photons into electrical charges.
80
What does TFT stand for?
Thin-film transistor
81
What is the purpose of a TFT in indirect DR imaging?
Collects light from the scintillator (indirect DR) and converts it to an electrical signal.
82
What is the purpose of a TFT in direct DR imaging?
Collects and transmits electrical signals from the photoconductor (direct DR) to the ADC (analog-to-digital converter).
83
What is the fill factor of a pixel?
The percentage of the pixel face that is sensitive to x-rays — approximately 80%.
## Footnote
The remaining 20% is made up of electronic components like conductors, capacitors, and the TFT itself.
84
What is amorphous selenium used for?
It is the material used in direct DR systems to convert x-rays directly into an electrical signal.
85
What role does a-Se play in the DR system?
It serves as both the capture element and the coupling element in the imaging process.
86
What are synonyms for detector elements?
DEL, dexel, pixel detector, pixel face
87
What is information called in pre-processing?
Raw data
88
What is the function of the ADC (Analog-to-Digital Converter)?
The ADC converts analog data to digital data through sampling and quantization to produce a digital image.
89
What does sampling frequency determine?
It determines how often the analog signal is reproduced in its digitized form.
## Footnote
↑ Sampling frequency → ↑ pixel density → ↑ spatial resolution.
90
How does increasing sampling frequency impact pixel density and spatial resolution?
Increasing sampling frequency increases pixel density and increases spatial resolution
91
What is pixel density?
The number of pixels per unit area.
92
What is the purpose of preprocessing?
It is largely automatic and improves image contrast while reducing artifacts by providing electronic calibration to correct pixel, row, and column response differences.
93
What is a defective pixel and how is it corrected?
A dead or unresponsive pixel. It is corrected through interpolation, where adjacent pixel values are averaged and assigned to the defective pixel.
94
What is image lag and how is it corrected?
A residual electronic image that remains after exposure (ghosting). It is corrected using offset correction, which applies an offset voltage before the next image is acquired (turning it off/on again).
95
What is line noise and how is it corrected?
Voltage variations along pixel rows or columns that cause linear artifacts. It is corrected using data from the dark reference zone (voltage correction) (color mimic).
96
What occurs during quantization?
Each pixel is assigned a numerical brightness value that determines the precision of recorded data points.
97
What is rescaling (automatic rescaling)?
It maintains consistent image brightness regardless of minor overexposure or underexposure.
98
What is flat fielding?
A process that equalizes each pixel’s response to a uniform x-ray beam and corrects for heel-effect brightness variations. It averages both pixels.
99
What is a phrase to remember to take advantage of a heel-effect with flat fielding?
Fat Cath. Put the thicker part towards the cathode and thinner towards the anode.
100
What is dead pixel correction?
The interpolation process that assigns a value to a dead pixel based on surrounding pixel values. (Mimic and blend to those around it)
101
What is a histogram?
A graphical representation of all pixel values in an image before edge detection and rescaling.
102
What does the horizontal axis of a histogram represent?
Pixel intensity (black to white).
103
What does the vertical axis of a histogram represent?
Number of pixels for each intensity value.
104
When looking at a histogram illustration with pixel intensity from 0-250, which side has white areas and which side has black?
Left are black areas, grey in middle, white on right.
105
What is histogram analysis?
The process where the computer compares the image histogram to a pre-set model specific to the anatomic region.
106
What are Values of Interest (VOI)?
The range of pixel values from the histogram used for image display.
107
What can cause a histogram analysis error?
Failure to detect collimation edges correctly, leading to images that appear too bright or too dark.
108
What is grayscale?
The number of different shades of gray that can be displayed by the computer system.
109
What is edge enhancement (high-pass filtering)?
A postprocessing technique that improves visibility of small, high-contrast structures.
110
What is equalization?
Adjusts image exposure by darkening light areas and lightening dark areas.
111
What is smoothing (low-pass filtering)?
Reduces image noise but may decrease spatial resolution.
112
What are Values of Interest (VOI) used for?
To define the range of histogram data included in the displayed image.
113
What is a Look-Up Table (LUT)?
A post-histogram processing method used to adjust brightness and grayscale. Can invert grayscale or change contrast.
114
What does the steepness of the LUT indicate?
The steepness of the LUT graph indicates contrast level (steeper = higher contrast).
115
How is contrast changed with a LUT?
By changing pixel values
116
What is post-processing?
Software operations performed manually by the technologist or radiologist to optimize image display for diagnosis.
117
Who performs post-processing?
Technologists, radiologists, clinicians, or other medical providers.
118
What is this common post-processing tool and its purposes: Annotation?
Adds text or labels to the image.
119
What is this common post-processing tool and its purposes: Window level?
Adjusts brightness.
120
What does an increase in Window level do to brightness?
Increases brightness (direct relationship).
121
What does window width control?
Image contrast.
122
How does an increase in window width affect contrast?
Increasing window width (wide width) decreases contrast. (Inverse relationship)
123
What is this common post-processing tool and its purposes: Magnification?
Zooms in to improve visualization.
124
What is this common post-processing tool and its purposes: Image Flip?
Changes orientation of the image.
125
What is this common post-processing tool and its purposes: Image Inversion?
Reverses black and white areas.
126
What is this common post-processing tool and its purposes: Subtraction (Direct Subtraction Angiography)?
Enhances vascular structures by removing background.
127
What is this common post-processing tool and its purposes: Pixel Shift?
Corrects for patient motion between images.
128
What is this common post-processing tool and its purposes: ROI (Region of Interest)?
Measures average pixel value for quantitative data.
129
What is electronic cropping or masking (shuttering)?
Used to remove bright edges or regions outside the radiation field that don’t contain useful data.
130
What is stitching?
Combines multiple overlapping images to display large anatomy as a single seamless image.
131
What is this post-processing tool?
Edge enhancement
132
What is this post-processing tool? (A w/o, B w/)
Equalization
133
What is this post-processing tool?
Contrast enhancement
134
What is this post-processing tool?
Subtraction
135
What is this post-processing tool? (A w/o, B w/)
Smoothing
136
What is this post-processing tool?
Inversion (black/white)
137
What is dose creep?
Overexposing patients with the intention of correcting the resulting images with post processing
138
What is dose creep the result of?
Technologists not adjusting exposure factors like they would with film as digital has a wider range of capabilities
139
What specific technical factor are techs abusing with "dose creep" to avoid quantum mottle?
They use high mAs values to reduce quantum mottle, but this overdoses the patient
140
If you don't change technical factors between lateral and AP views when taken consecutively, what is possible?
Overall patient dose to increase
141
What is EIᴛ?
Target exposure index.
What you "want" the exposure to be/optimal exposure
142
What is EI?
Exposure index.
What you "have"/the exposure you made
143
What is DI?
Deviation index.
The difference between what you want (EIᴛ) and what you get (EI)
RAD 142
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