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ICS - RADIOLOGY > 6 - Image Receptors 2 > Flashcards

6 - Image Receptors 2 Flashcards

1
Q

barrier wrapped film: what does the barrier provide?

A

infection control

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2
Q

outer plastic wrapping: 3 uses?

A
  • keeps film dry & saliva free
  • protects film from light damage: fogging
  • indicates the correct orientation of the film i the mouth: white side towards xray tube
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3
Q

black paper: uses?

A
  • protect film from light leakage

- stiffens and supports film, to prevent crimp/pressure marks on the film

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4
Q

lead foil: composed of? uses?

A
  • composed of a mixture of lead and aluminium (has distinct pattern embossed into lead)
  • readily absorbs xrays
  • prevents back scatter
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5
Q

film: what are the 5 layers?

A
  • base: plastic (polyester), blue anti glare tint
  • 2 adhesive layers
  • double emulsion layers
  • protective layer of gelatine
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6
Q 
emulsion: 
what is suspended in the gelatin? what is it made of?
what does the gelatin allow?
adhesive layer: what does it stick?
supercoat: consists of?
A
  • silver halide crystals; made of silver bromide, silver iodide or both
  • allows even distribution of crystals
  • gelatin absorbs liquid readily to allow processing
  • sticks emulsion to the base
  • consists of a protective layer of gelatin
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7
Q

image formation: on direct action (intra oral film) - how is latent image produced?

A

x-ray photon hits silver halide crystals within emulsion of film
silver halide crystal becomes sensitised, thereby producing the latent image

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8
Q

what is the latent image?
how is it made visible to the naked eye?
what is the main reaction?

A
  • the pattern produced within the emulsion by the sensitizing of silver bromide/iodide crystals, either by light or xrays
  • done by chemical reactions that take place during image processing
  • the reduction of silver bromide crystals to black metallic silver
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9
Q

what is film speed?

what does it mean when the film is “fast”?

A
  • the exposure required to produce a given amount of blackening (optical density) on an image
  • it means that less exposure is required for a given film blackening and therefore lower radiation dose to the patient
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10
Q

film speed:
dependent on?
what is compromised with fast film speed?

A
  • film speed is dependent on the size of crystals in the emulsion.
  • larger crystals, faster speed
  • larger crystals mean faster speed, but also reduced detail in the x-ray
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11
Q 
indirect film:
sensitive to?
light produced by?
relationship between light produced and x-rays that hit the screen?
how is exposure affected?
A
  • sensitive primarily to light
  • light produced by intensifying screens inside the cassette
  • more light produced, more x-rays hit the screens
  • amount of radiation required to expose the film is reduced, meaning that exposure is reduced.
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12
Q

intensifying screen - layers? what is each made of?

A
  • base: polyester
  • reflective layer
  • phosphor layer: fluorescent phosphors, emit light when excited by x-rays
  • supercoat: protects phosphor layer from damage
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13
Q

radiographic film susceptible to damage by? how is the damage specifically done?

A
  • pressure marks - crimp/bend marks

- pressure sensitises the silver halide crystals

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14
Q

best ways to handle film and prevent damage?

A

handle film with care:

  • hold by corners/sides
  • beware of leaving fingerprints on image
  • wet or dry emulsion easily scratched
  • support extraoral film when feeding into processor
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15
Q

film storage: ideal conditions?

A
  • cool; not too cool
  • dry; not too dry
  • away from radiation: xrays, heat
  • stock rotation to prevent using old film
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16
Q

image formation: direct action?

A
  • xray photon hits silver halide crystals within emulsion of film
  • silver halide crystal becomes sensitised
  • latent image produced
17
Q

image formation: indirect action?

A
  • xray photon hits phosphor crystal
  • gives off light
  • light hits silver halide crystals within film emulsion
  • silver halide crystals sensitized
  • latent image produced
18
Q

processing of image - FILM:

what are the methods of film processing?

A
  • automatic
  • manual
  • instant
19
Q

what are the 5 stages of film processing?

A
  • develop: make latent image visible
  • wash: stop development and remove developer from film (manual only)
  • fix: make image permanent
  • wash: stop fix and remove residual fixer
  • dry: easier handled, prevent damage
20
Q

components of automatic image processor?

A
  • feed in rollers
  • developer rack
  • fixer rack
  • wash rack
  • dryer
21
Q

developing:
sensitised silver halide crystals are acted on by what substances in the developing agent?
what is the chemical reaction involved?
how is blackening on the film achieved?

A
  • silver crystals are acted upon by phenidone and hydroquinone
  • silver bromide undergoes reduction into silver plus bromide
  • silver is in the form of black metallic silver; therefore producing blackening
22
Q 
developer:
developing agents?
activator + function?
restrainer + function?
preservative + function?
solvent?
A
  • phenidone and hydroquinone
  • calcium carbonate. it controls the activity of the developing agents
  • potassium bromide. it stops developer from working on unexposed crystals
  • sodium sulphite. it slows down oxidation
  • water
23
Q

action of developing agents on silver halide crystals is dependent on?

A
  • time: if too long, image will be dark. if short, image will be light.
  • temperature: too hot, image too dark. too cold, image too light
  • concentration: too strong - dark. too weak, image too light
24
Q

fixing: what do the fixing agents do?

A
  • change unexposed silver halide to soluble compound so they can be washed away (wash stage)
  • acid maintains the pH and neutralizes the developer
25
Q 
fixer: 
clearing agent?
acidifier + function?
hardener?
preservative?
solvent?
A
  • ammonium thiosulphate
  • acetic acid (maintain pH)
  • aluminium chloride
  • sodium sulphite
  • water
26
Q

action of fixing agents on silver halide crystal is dependent on?
how is it different from the developing stage?
what happens when image is over or under fixed?

A
  • time, temperature, concentration
  • not as critical as developing stage
  • over fixed: image will be removed from film
  • under fixed: image will have green tinge and will not archive well
27
Q

wash: when to carry out for the manual process?

what does it do? x2

A
  • between development & fix,
  • between fix & dry stages
  • stops action of developer, reduces carryover
  • remove unexposed silver halide crystals once made soluble by fixer
28
Q

wash: when to carry out for automatic stage?

what is the purpose?

A
  • only between fix & dry

- washes away unexposed silver halide crystals made soluble by the fixer

29
Q

wash: what happens when wash is insufficient?

A
  • film will feel tacky
  • will/may also have a green or silvered appearance
  • will not archive well, image will deteriorate
30
Q

drying: why should image be dried well

A
  • reduce possibility of damage to emulsion
31
Q

automatic processing: advantages? x5

A
  • consistent
  • less operator dependent
  • temperature controlled
  • time controlled
  • less chance to damage film
32
Q

manual processing: advantage?

disadvantages? x3

A
  • if done well can be as good as automatic
  • very operator dependent
  • temp must be monitored
  • time must be accurate
33
Q

instant processing: 4 advantages and 1 disadvantage?

A
  • chemicals in pouch attached to film
  • no large amount of chemicals to dispose of
  • very quick
  • convenient
  • films do not archive well
34
Q

what are the 3 steps to correct processing?

A
  • develop correct density of image: not too dark or light
  • fix & wash: for good archiving
  • dry: so film is undamaged
35
Q

health & safety: what does COSHH stand for?

A

control of substances hazardous to health

36
Q

manufacturers must provide what for potentially hazardous substances?

A

Material Safety Data Sheet

37
Q

developer: how harmful? possible risk of? skin contact causes?
inhalation?

A
  • limited evidence of carcinogenic effect
  • irreversible effects
  • may cause sensitization
  • inhalation considered low hazard
38
Q

fixer: harmful? what to beware of? releases what potentially harmful substances upon contact with strong acid or alkali?

A
  • not hazardous
  • is corrosive
  • can release sulphur dioxide or ammonia on contact with strong acid/alkali, potentially harmful
39
Q

recommended handling for image processing agents?

A
  • adequate ventilation: 10 or more room volumes per hour

- PPE: googles, respirator, apron and gloves both chemical resistant

ICS - RADIOLOGY (14 decks)

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