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Image science principles > digital imaging > Flashcards

digital imaging Flashcards

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1
Q

analogue images

A
  • have a continuously varying density across them
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2
Q

digital images

A
  • Have discrete pixels with numerical density values
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3
Q

digital imaging series

A
  • generation
  • processing
  • archiving
  • presentation
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4
Q

types of digital radiography

A

computed radiography

digital radiography

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5
Q

computed radiography

A
  • uses imaging plates which need developing in a processor
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6
Q

digital radiography

A
  • acquires an image directly without using a processor
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7
Q

main digital image detector functions

A
  • capture - absorbing x-rays
  • coupling - linkage between the capture element and converter
  • conversion - change of x-ray energy into an electrical signal which can be read
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8
Q

advantages of digital radiography

A
  • time-efficient - receive image immediately
  • ## reduction of unsharpness - no spread of light
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9
Q

advantages of indirect imaging

A
  • can reduce dose/exposure
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10
Q

digital imaging (DR)

A
  • Image does not need to be procecessed
  • the image is sent to the computer via wireless connection
  • the imaging detectors can either be fixed plates in a vertical or table bucky or portable cassettes
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11
Q

Selenium drum detector system

A
  • the photoconductor is made of amorphous selenium ( generates an electrical charge
  • has a detector drum
  • A-D converter - readout process
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12
Q

In ….. x-ray energy is converted directly into electrical signal

A

DDR

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13
Q

a simple conversion process of x-rays to electronic signal reduces noise in……

A

DDR

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14
Q

one advantage for ….. is good image resolution

A

DDR

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15
Q

one advantage for… is reduction in patient dose, since x-ray exposure can be reduced

A

CR

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16
Q

…. can give a salt and pepper appearance

A

CR

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17
Q

one advantage of… is amplification of signal

A

CR

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18
Q

one advantage of … is image sharpness

A

DDR

19
Q

One disadvantage of …. is that the extra energy conversion process produces image noise

A

CR

20
Q

in…. X-rays first strike a light-producing layer, light is then used to produce an electrical signal in the detector plate

A

CR

21
Q

Dose creep occurs in …

A

DDR

22
Q

….. gives a lower dose to the patient

A

CR

23
Q

…. uses cassettes, containing imaging plates which need processing

A

CR

24
Q

…. Acquires an image without using a cassette or processor

A

DDR

25
Q

………. can be linked via PACS

A

Both CR and DDR

26
Q

…. is a direct method

A

DDR

27
Q

…. is an indirect method

A

CR

28
Q

one disadvantage of …. is that the light spread produces image fuzziness

A

CR

29
Q

….. has a photoconductor of amorphous selenium

A

DDR

30
Q

……. has a scintillation crystal made of caesium iodide activated with Thalium

A

CR

31
Q

a simple conversion process of x-rays to electronic signal reduces spatial blurring in ……

A

DDR

32
Q

purpose of a photoconductor

A
  • absorbs light and then produces an electrical charge
33
Q

flat-panel detector system

A

the photoconductor is made of Amorphous selenium

uses a TFT Array read-out process.

33
Q

flat-panel detector system

A

the photoconductor is made of Amorphous selenium

uses a TFT Array read-out process.

34
Q

flat-panel detector system

A

the photoconductor is made of Amorphous selenium

uses a TFT Array read-out process.

35
Q

types of Amorphous Selenium DR systems

A
  • selenium drum detector system

- flat-panel detector system

36
Q

indirect DR

A
  • each cell in the detector has a top layer of a scintillation crystal (made of CsI (caesium iodide) activated with thallium - which produces light when hit by x-rays
  • below this, an amorphous silicon photodiode converts the light into an electric charge
37
Q

types of CCD indirect radiography systems

A

lens-coupled CCD based system

Slot scan CCD based system

38
Q

lens-coupled CCD based system

A

x-rays are converted into light by the scintillation crystals
- light passes through an optical lens and light is received by the charged-couple device

39
Q

Amorphous silicon indirect DR system

A

x-rays are converted into light by the scintillation crystals

  • this light is received by the Amorpous silicon photodiode
  • light energy is converted to electrical energy and is received by the TFT array
40
Q

what is quantum mottle

A

at very low mAs values, random fluctuations in x-ray intensity beam start to show

  • image can appear grainy
41
Q

CR system

A

x-rays hit the first storage phosphor IP and are stored

a laser is emitted and hits the second storage phosphor IP

a blue light is then emitted and is received by the photomultiplier

then the photomultiplier sends this light to an A/D converter where an electrical charge is produced

42
Q

what is image noise

A
  • random fluctuations in signal, due to imperfections in image recording/transfer process
43
Q

sources of noise

A
  • background scatter
  • detector faults
  • random electrical fluctuations
  • quantum mottle

Image science principles (12 decks)

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