6 - Image Receptors 2 Flashcards
1
Q
barrier wrapped film: what does the barrier provide?
A
infection control
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
3
Q
black paper: uses?
A
- protect film from light leakage
- stiffens and supports film, to prevent crimp/pressure marks on the film
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
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
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
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
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
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
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
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.
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
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
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
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
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
```
fixer:
clearing agent?
acidifier + function?
hardener?
preservative?
solvent?
```
- ammonium thiosulphate
- acetic acid (maintain pH)
- aluminium chloride
- sodium sulphite
- water
26
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?
- 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
wash: when to carry out for the manual process?
| what does it do? x2
- between development & fix,
- between fix & dry stages
- stops action of developer, reduces carryover
- remove unexposed silver halide crystals once made soluble by fixer
28
wash: when to carry out for automatic stage?
| what is the purpose?
- only between fix & dry
| - washes away unexposed silver halide crystals made soluble by the fixer
29
wash: what happens when wash is insufficient?
- film will feel tacky
- will/may also have a green or silvered appearance
- will not archive well, image will deteriorate
30
drying: why should image be dried well
- reduce possibility of damage to emulsion
31
automatic processing: advantages? x5
- consistent
- less operator dependent
- temperature controlled
- time controlled
- less chance to damage film
32
manual processing: advantage?
| disadvantages? x3
- if done well can be as good as automatic
- very operator dependent
- temp must be monitored
- time must be accurate
33
instant processing: 4 advantages and 1 disadvantage?
- chemicals in pouch attached to film
- no large amount of chemicals to dispose of
- very quick
- convenient
- films do not archive well
34
what are the 3 steps to correct processing?
- develop correct density of image: not too dark or light
- fix & wash: for good archiving
- dry: so film is undamaged
35
health & safety: what does COSHH stand for?
control of substances hazardous to health
36
manufacturers must provide what for potentially hazardous substances?
Material Safety Data Sheet
37
developer: how harmful? possible risk of? skin contact causes?
inhalation?
- limited evidence of carcinogenic effect
- irreversible effects
- may cause sensitization
- inhalation considered low hazard
38
fixer: harmful? what to beware of? releases what potentially harmful substances upon contact with strong acid or alkali?
- not hazardous
- is corrosive
- can release sulphur dioxide or ammonia on contact with strong acid/alkali, potentially harmful
39
recommended handling for image processing agents?
- adequate ventilation: 10 or more room volumes per hour
| - PPE: googles, respirator, apron and gloves both chemical resistant
