Image Receptors 2 Flashcards
what are the two types of film available ?
- Direct
- Indirect
Direct film is only used for?
Intra-oral radiographs
When using a direct action film it can be placed in a sealed plastic barrier envelope, what does it do?
Protects the film from saliva and is torn open on complex of the x-ray and disposed of in the clinical waste leaving the clean film packet ready to handle
When you open the packet and remove the outer layer, you will reveal black paper what does it do?
Helps protect the film from light leakage. it also helps to prevent crimp and pressure marks on the film by providing a bit of support
Inside the black paper you will find the film sitting on shiny layer. the shiny layer is lead foil what does it do?
prevents degradation of image by absorbing the scatter.
what does film emulsion mean?
the layer that reacts with the x-rays to form the image. it is comprised of silver halide crystals usually silver bromide, suspended in gelatin
what are the two functions of gelatin?
- allows even distribution of the crystals
- absorbs liquid easily which helps during processing
what is a latent image?
when an x-ray photon hits the silver halide crystal within the emulsion it becomes sensitised
what are the two speeds in which x-rays are available ?
Slow and fast
What does sensitivity of the film depend upon?
on the size of the crystals in the emulsion - the larger the crystals the faster the film speed and the lower the amount of x-rays required to produce an image
- the larger the crystals, the less detail you have on the film. it has a lower resolution
Film size is just the same as digital receptor sizes, 0,1,2, and 4, what do they correspond to?
0 - anteriors and children
1 - canines
2 - adult posteriors and bitewings and children over 10
4 - for occlusals
what is indirect action film used for?
extra-oral radiography
when would u use indirect action films?
For DPT’s, lateral cephs and other head and neck radiography
what is the difference between indirect and direct action films?
Indirect film is sensitive to light rather than x-rays, the x-rays react with the intensifying screens to produce light which then exposes the film. This system allows you to reduce the exposure required to produce an image and therefore the dose received by the patient
what does the intensifying screen do?
allows a significant reduction in the radiation exposure