Image Receptors- Film Flashcards
What is the outer plastic layer for?
Keeps film dry
Protects film from light
Indicates correct orientation of film ( white side towards x Ray tube)
What is the black paper for?
Protects from light
Stiffens and supports film
What is lead foil for?
Absorbs x Ray’s
Prevents scatter
What is the film made up of?
Plastic base Anti glare tint- blue Adhesive layer Double emulsion Protective gelatin layer
What is the emulsion made up of?
Silver halide crystals suspended in gelatin
What is the purpose of the gelatin?
Allows even distribution of crystals
Absorbs liquid readily to allow processing
What does the adhesive layer do?
Sticks the emulsion to the base
How is an image formed?
Direct action
Xrays photons hits silver halide crystals in emulsion
Crystals become sensitised
Latent image produced
What is a latent image?
Pattern produced within emulsion
Not visa lie to naked eye
What is film speed?
Sensitivity of film to xrays
Exposure required to produce a given amount of blackening
Dependant on the size of crystal
How does the size of crystals affect film speed?
Larger crystals = faster film speed
How does the film speed affect the amount of xrays required to produce image?
Faster film speed requires less xrays to produce image
Where is indirect film used?
Extra oral radiographs
What are indirect action films sensitive to?
Primarily light
Where is the light produced re. Indirect film?
Intensifying screen
What effect does the intensifying screen have on dose?
Reduces exposure required to produce image therefore reduces dose
What is the intensifying screen made up of?
Base- polyester
Reflective layer
Phosphor layer
Super coat
What does phosphor layer do?
Emits light when excited by xrays
What demos the super coat do?
Protects phosphor layer from damage
How is image formed re. Indirect film?
X-ray photon hits phosphor crystals in intensifying screen
Light given off
Light hits silver halide crystals within film emulsion
Latent image produced
What is a film packet made up from?
Barrier wrap Outer plastic Black paper Lead foil Film Emulsion
