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Advanced Image Aquisition > Digital Imaging > Flashcards

Digital Imaging Flashcards

(68 cards)

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1
Q

Advantages of computer use in radiography

A 
Generators more precise
Increased diagnostic power
Increased efficiency
Transmission of images
Increased storage capacity
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2
Q

Analog

A

Continuously variable signal (electric currents)

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3
Q

Digital signal

A

Signal converted to digital form and then used in a display or computation. Defined quantities of current.
Easier to read-more precise

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4
Q

Integrated circuit chip

A

Small semiconductor chip in which millions of circuit elements are placed.
Allows computers today to be much smaller than 1st and 2nd generation

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5
Q

Software

A

Invisible
Instructions (programs)
Soul of computer

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6
Q

Hardware

A

Visible
Nuts and bolts
Body of computer

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7
Q

Binary number system

A

Number system computers use to operate. 0s and 1s.

Each single binary number is called a bit

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8
Q

Computers are rated in terms of

A

Byte memory

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9
Q

Systems software

A

User friendly. Make it easy to operate

Ex: windows

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10
Q

Applications software

A

Carry out user function.
Apps.
Ex: word

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11
Q

Computer language

A

Allows us to write programs in language similar to ours

Ex: java

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12
Q

Processing of computer hardware

A

Electronic circuitry that does the actual computations and the memory that supports this

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13
Q

Central processing unit or microprocessor

A

Acts as a nucleus to computer

Contains control unit and logic unit

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14
Q

Control unit of CPU

A

Directs incoming data to arithmetic or memory unit
Interprets users program instructions in proper sequence
When task complete transfers information to output device

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15
Q

Logic unit of CPU

A

Performs logic and numeric calculations

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16
Q

Bus

A

Connects control unit and arithmetic unit and all other components during processing

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17
Q

System clock

A

Determines speed of computer

GHz, MIPS

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18
Q

Main memory/storage memory

A

Long term storage

Stores programs and data files

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19
Q

Active memory or random access memory (RAM)

A

Memory replaces old with new info

Short term

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20
Q

ROM

A

Read only memory
Operating instructions
Rarely changed

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21
Q

RAM

A

Random access memory
Temporary storage during use
Gets changed

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22
Q

Optical disks

A

Stores digital data in mirrored surface with laser light

Disk drive

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23
Q

External hard disc drive

A

Stack of discs that store data magnetically
Take them from place to place
Used for backing up computer

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24
Q

Solid state storage devices

A

Store data using flash memory

Type of erasable programmable read only memory (EEPROM)

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25
USB flash drives
Also use flash memory
26
Input
Allows us to put in information Keyboard, mouse, trackball, light pen, touchpad, scanner, fax machine, imagine system, audio and video devices, voice recognition, sensors, biological input devices (thumb print)
27
Output
Allow the computer to give us information From memory to storage or user. Display screen, printer, speaker, laser camera/processor
28
Communications
From one computer to another | Requires modem if communication lines are analog
29
Information can be transferred through:
Electric cable Electric wire Atmosphere Fiber optic cable
30
Information can be transferred AS:
Electric current, light, radio frequency, digital bit system
31
What is a digital image?
Image that has been converted to numbers Image is displayed as a matrix of intensities that correlate to numerical values These numerical values can be stored and manipulated by computer
32
Fourier transformation
Mathematical method used to create computerized medical images Allows digital and computerized imaging to be
33
Matrix
Arrangement of columns and rows of cells that make up the image
34
The larger the matrix
The greater the spatial resolution
35
Pixel
Individual cells of matrix
36
The smaller the pixel size
The greater the spatial resolution
37
Pixel density
Number of pixels per unit area | For a given FOV, pixel density increases, pixel size decreases, increase spatial resolution
38
Pixel pitch
Distance from the center of one pixel to the center of the adjacent pixel
39
Decreased pixel pitch
Increased spatial resolution
40
Voxel
Volume element | 3D volume of tissue that is represented by a certain pixel
41
Pixel value
Numerical value of each pixel Lower number means white/bright Higher number means darker
42
Bit depth
Number of shades of gray possible for a system to acquire and display.
43
Increased bit depth
Increased contrast resolution
44
Digital imaging processing
3 steps: Scanning Sampling Quantization
45
Sampling frequency
Frequency at which the analog signal is sampled | CR: increased sampling frequency=increased spatial resolution=decreased pixel pitch
46
Nyquist frequency
Sampling frequency must be greater than 2x the signal frequency to avoid aliasing (Moire effect)
47
Histogram
Graphic display of pixel values of a given digital image
48
Automatic rescaling
Process employed during histogram analysis that maintains consistent image brightness and contrast
49
Exposure data recognition
Ability of a digital system to identify raw background exposure field so that data outside o the anatomy may be excluded from histogram analysis and exposure indicator calculations
50
Window level
Image brightness | Sets mid point of the range of densities visible in the image
51
Window width
Controls image contrast | Increased width longer scale of contrast
52
Low pass filtering
Smoothing | Used to remove high frequency noise
53
Band pass filtering
Selects a band of frequencies to delete or amplify
54
High pass filtering
Edge enhancement
55
Convolution
Modifying pixel values to enhance of suppress visual characteristics of an image
56
Reconciliation
Returning pixel value to original level
57
Silicon TFT flat panel imaging system
Scintillator-CSI or gadolinium oxysulfide conveys X-ray to light Silicon-concerts light to electron TFT-determines when charge will be released from capacitor. Releases electrons in orderly fashion ADC-converts electrons to number value
58
Advantage of silicon TFT
High DQE which decreases patient dose
59
Disadvantages of silicon TFT
Loss of resolution from light divergence of scintillation phosphor
60
CCD
Scintillation- CsI or gadolinium oxysulfide converts X-ray to light CCD-converts light to electrical signal and sends to computer ADC-converts electrons to number value
61
Advantage of CCD
100% fill factor, 85% light conversion efficiency
62
Disadvantage of CCD
Pixel size, a lot of heat produced high power requirements
63
CMOS complimentary metal oxide semiconductor
Scintillator-concerts X-ray to light CMOS-converts light to electrons and sends to computer ADC-confers electrons to number
64
Advantage of CMOS
Smaller and faster than CCD, lower power consumption
65
Disadvantage of CMOS
More susceptible to noise
66
Selenium TFT
Selenium-charged prior to exposure concerts X-rays to electrons Electrodes collect electrons TFT sends signal to computer in orderly fashion ADC-Change electrons to numbers THIS IS THE ONLY DIRECT APPROACH
67
Advantage of selenium
No light conversion, no light divergence which means increased resolution
68
Disadvantage of selenium
Lower DQE than silicon, need to use more dose

Advanced Image Aquisition (7 decks)

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