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Module 4 - radiology > Image Receptors > Flashcards

Image Receptors Flashcards

1
Q

What type of x-rays use direct film image production?

A

intra oral

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2
Q

what is direct film image production?

A

x-rays act directly on silver halide crystals in film emulsion

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3
Q

what type of x-rays use indirect film image production?

A

extra-oral

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4
Q

what is indirect film?

A

light from intensifying screens act on silver halide crystals in film emulsion

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5
Q

what are the 2 types of digital image production?

A

solid state
PSP

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6
Q

What type of sensors produce solid state digital images?

A

CCD or CMOS

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7
Q

What type of digital image production is tolerated better?

A

PSP

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8
Q

What is a phosphor plate?

A

storage plate that converts existing film based imaging system to a digital format that can be integrated into a computer or network system

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9
Q

what part of the phosphor plate is exposed to x-ray photons and scanned by the red laser?

A

phosphor layer

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10
Q

what produces a latent image?

A

x-ray energy stored in the electrons of the phosphor crystals (trapped signal)

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11
Q

in PSP, what is released as blue light?

A

stored energy

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12
Q

in PSP, what converts light to a digital signal?

A

ACD

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13
Q

In PSP, what represents the shades of grey which form the image on the monitor?

A

numerical value assigned to each pixel according to the intensity of detected light

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14
Q

how is the image on the phosphor plate erased?

A

exposing the phosphor to bright light - releases any remaining trapped energy in the phosphor electrons

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15
Q

what is the phosphor coating on the phosphor plate?

A

barium fluoride

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16
Q

What is CCD?

A

Charged-coupled device

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17
Q

what is CCD used for?

A

digital radiography for the indirect conversion of x-ray photons into an electric charge

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18
Q

what gives off light in CCD?

A

X-rays hit the scintillator layer within the sensor

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19
Q

what makes up pixels of an CCD image?

A

light hits the photosensitive cells within a very thin piece of silicon

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20
Q

in CCD what is converted into an electrical signal?

A

the charge electrons within each pixel being released

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21
Q

what is converted to produce an image in CCD?

A

ELECTRICAL SIGNAL

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22
Q

What differs CCD to CMOS?

A

CCD - pixels connected to form lines of pixels
CMOS - individual pixels

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23
Q

what is exposure?

A

the amount of x-rays to produce an image

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24
Q

what is PACS?

A

picture archiving and communication system

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25
Q

what are 0, 1, 2 PSP sizes used for?

A

periapical and bitewings

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26
Q

what are 0, 1 PSP sizes used for?

A

periapical anterior mouth of adult and all regions for children

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27
Q

what is 2 PSP size used for?

A

posterior mouth of adults

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28
Q

what is size 4 PSP used for?

A

occlusal

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29
Q

what size of solid state receptor would you normally use?

30
Q

what is the lead foil in film packet?

A

composed of lead and aluminium
- readily absorbs x-rays
- prevents black scatter

31
Q

what are the 4 layers of dental film?

A
  • super coat
  • base
  • adhesive layer
  • emulsion
32
Q

what is the emulsion layer of a dental film made of?

A

silver halide crystals (silver bromide and silver iodide) suspended in gelatine

33
Q

what is the super coat of dental film made of?

34
Q

what does the adhesive layer in the dental film do?

A

sticks emulsion to the base

35
Q

explain the image formation - direct action (intra oral)

A
  • x-ray photons hit silver halide crystals within the emulsion of the film
  • silver halide crystals become sensitised
  • latent image is produced
  • silver bromide crystals are reduced to black metabolic silver
36
Q

what is a latent image?

A

the pattern produced within the emulsion by the sensitising of silver bromide/ iodide crystals by light/ x-rays

37
Q

what effects film speed?

A
  • sensitivity of film to x-rays
  • exposure required to produce a given amount of blackening on an image
  • larger the crystals the faster the film speed
38
Q

how does crystal size affect detail?

A

larger crystals = reduced detail

39
Q

how is light produced in extra oral/ indirect film?

A

intensifying screens inside cassette

40
Q

what is a positive and negative of intensifying screens?

A

reduce the dose required
reduce detail

41
Q

what are the layers of an intensifying screen?

A

reflective layer
phosphor layer
supercoat

42
Q

explain extra oral image formation?

A
  • x-ray photons hits the phosphor crystals in the intensifying screen and give off light
  • light hits silver halide crystals within the film emulsion
  • silver halide crystals become sensitised
  • latent image produced
43
Q

how should films be stored?

A

cool
dry
away from radiation - x-ray, heat
stock rotation

44
Q

what are the 3 types of film processing?

A

automatic, manual and instant

45
Q

what are the 5 stages of film processing?

A
  • develop (make latent image visible)
  • wash (stop development and remove from film)
  • fix (make image permanent)
  • wash (stop fix and remove residual fixer)
  • dry (easier handled, prevent damage)
46
Q

what does developing do?

A

making the image visible

47
Q

how is an image made visible?

A
  • sensitised silver halide crystals are acted on by developing agents (phenidone and hydroquinone)
  • silver bromide reduced to silver plus bromide
  • silver is in the form of black metallic silver thus giving the blackening on the film
48
Q

what are developing agents?

A

phenidone and hydroquinone

49
Q

what is the activator and development and what does it do?

A

calcium carbonate - controls the activity of the developing agents

50
Q

what is the restrainer in development and what does it do?

A

potassium bromide - stops developer working on unexposed crystals

51
Q

what is the preservative in development and what does it do?

A

sodium sulphite - slows down oxidation

52
Q

what is the solvent in development?

53
Q

what is the action of developing agents dependant on?

A

time
temperature
concentration

54
Q

how is the image made permanent?

A

fixing agents change unexposed silver halide to soluble compound do they can be washed away

55
Q

what is the clearing agent in fixing?

A

ammonium thiosulphate

56
Q

what is the acidifier in fixing?

A

acetic acid (maintains pH)

57
Q

What is the hardener in fixing?

A

aluminium chloride

58
Q

what is the preservative in fixing?

A

sodium sulphite

59
Q

what is the solvent in fixing?

60
Q

what is the action of fixing agents dependant on?

A

time
temperature
concentration

61
Q

what happens if an image is over fixed?

A

fixed image will be removed from film

62
Q

what happens if an image is under fixed?

A

appear to have a green tinge and will not archive well

63
Q

what are the 3 types of washing?

A

manual
automatic
instant

64
Q

when does manual washing take place?

A

between dev. and fix
between fix and dry

65
Q

what does manual washing do?

A

stops action of developer and reduces carryover - removed unexposed silver halide crystals once made soluble by fixer

66
Q

when does automatic washing take place?

A

between fix and dry

67
Q

what does automatic washing do?

A

Remove unexposed silver halide crystals once made soluble by fixer.

68
Q

what happens if film not washed properly?

A

feel tacky, and may have a green or silvered appearance. Will not archive well so will deteriorate.

69
Q

what does drying ensure?

A

film is dry before it is handled and reduces the possibility of damage to emulsion

70
Q

what is the health and safety act?

A

health and safety at work act 1974

71
Q

what are the major components of the health and safety at work act 1974?

A

control of substances hazardous to health regulations (COSHH)
Risk assessment
adequate ventilation (10 or more room volumes per hour)

Module 4 - radiology (14 decks)

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