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Advanced Image Aquisition > Digital Imaging > Flashcards

Digital Imaging Flashcards

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
Q

USB flash drives

A

Also use flash memory

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26
Q

Input

A

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)

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27
Q

Output

A

Allow the computer to give us information
From memory to storage or user.
Display screen, printer, speaker, laser camera/processor

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28
Q

Communications

A

From one computer to another

Requires modem if communication lines are analog

29
Q

Information can be transferred through:

A

Electric cable
Electric wire
Atmosphere
Fiber optic cable

30
Q

Information can be transferred AS:

A

Electric current, light, radio frequency, digital bit system

31
Q

What is a digital image?

A

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
Q

Fourier transformation

A

Mathematical method used to create computerized medical images
Allows digital and computerized imaging to be

33
Q

Matrix

A

Arrangement of columns and rows of cells that make up the image

34
Q

The larger the matrix

A

The greater the spatial resolution

35
Q

Pixel

A

Individual cells of matrix

36
Q

The smaller the pixel size

A

The greater the spatial resolution

37
Q

Pixel density

A

Number of pixels per unit area

For a given FOV, pixel density increases, pixel size decreases, increase spatial resolution

38
Q

Pixel pitch

A

Distance from the center of one pixel to the center of the adjacent pixel

39
Q

Decreased pixel pitch

A

Increased spatial resolution

40
Q

Voxel

A

Volume element

3D volume of tissue that is represented by a certain pixel

41
Q

Pixel value

A

Numerical value of each pixel
Lower number means white/bright
Higher number means darker

42
Q

Bit depth

A

Number of shades of gray possible for a system to acquire and display.

43
Q

Increased bit depth

A

Increased contrast resolution

44
Q

Digital imaging processing

A

3 steps:
Scanning
Sampling
Quantization

45
Q

Sampling frequency

A

Frequency at which the analog signal is sampled

CR: increased sampling frequency=increased spatial resolution=decreased pixel pitch

46
Q

Nyquist frequency

A

Sampling frequency must be greater than 2x the signal frequency to avoid aliasing (Moire effect)

47
Q

Histogram

A

Graphic display of pixel values of a given digital image

48
Q

Automatic rescaling

A

Process employed during histogram analysis that maintains consistent image brightness and contrast

49
Q

Exposure data recognition

A

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
Q

Window level

A

Image brightness

Sets mid point of the range of densities visible in the image

51
Q

Window width

A

Controls image contrast

Increased width longer scale of contrast

52
Q

Low pass filtering

A

Smoothing

Used to remove high frequency noise

53
Q

Band pass filtering

A

Selects a band of frequencies to delete or amplify

54
Q

High pass filtering

A

Edge enhancement

55
Q

Convolution

A

Modifying pixel values to enhance of suppress visual characteristics of an image

56
Q

Reconciliation

A

Returning pixel value to original level

57
Q

Silicon TFT flat panel imaging system

A

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
Q

Advantage of silicon TFT

A

High DQE which decreases patient dose

59
Q

Disadvantages of silicon TFT

A

Loss of resolution from light divergence of scintillation phosphor

60
Q

CCD

A

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
Q

Advantage of CCD

A

100% fill factor, 85% light conversion efficiency

62
Q

Disadvantage of CCD

A

Pixel size, a lot of heat produced high power requirements

63
Q

CMOS complimentary metal oxide semiconductor

A

Scintillator-concerts X-ray to light
CMOS-converts light to electrons and sends to computer
ADC-confers electrons to number

64
Q

Advantage of CMOS

A

Smaller and faster than CCD, lower power consumption

65
Q

Disadvantage of CMOS

A

More susceptible to noise

66
Q

Selenium TFT

A

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
Q

Advantage of selenium

A

No light conversion, no light divergence which means increased resolution

68
Q

Disadvantage of selenium

A

Lower DQE than silicon, need to use more dose

Advanced Image Aquisition (7 decks)

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