OMR Flashcards
What makes up an X-ray film?
Emulsion Base
What is the emulsion component of the x-ray film?
Consists of * Photon Sensitive Silver Halide Grains * Suspension vehicle
What is the X-ray sensitive part of the X-ray film?
Silver Halide Grains
What happens to the silver halide grains when x-rays hit them?
A conformation change occurs which will expose an image during development ** chemically altered
What is the base component of the X-ray film?
Plastic supporting material
When the silver halide is chemically altered it creates a ____ _______.
Latent image
What makes up a film packet?
Lead foil backing (only on back side) Paper wrap Dental Film
What is the purpose of the lead foil backing?
To absorb stray x-rays
The bump on the film must always be pointing: away or towards the source of radiation?
Towards
The bump on the film should be orientated apically or coronally?
Coronally
The bump on the packet should be oriented: away or towards the source of radiation?
Away - this is the side o the film packet that has the lead foil
If the lead foil is oriented towards the source of radiation what can happen on the film?
The film will have crinkly pattern from the lead foil when developed
Size 0
Pedo
Size 1
Adult anterior
Size 2
Adult posterior
Size 3
Long posterior
Size 4
occlusal
The film speed depends on what?
The size of silver halide crystals
Faster the film speed the ______ the size of the silver halide crystals
Larger - the larger the crystals the more likely they are to be struck by an x-ray. Requires less radiation
Slower film speed the ______ the size of the silver halide crystals
Smaller - image is less grainy but requires more radiation to hit all of the small crystals
What is the silver halide chemically altered to?
Metallic silver compound
what is the purpose of the intensifying screens in the cassettes?
To use less radiation. Contains earth metals - once exposed by an X-ray the screen releases more photons to expose the film
What is a downside to cassettes?
Decreased definition. Panos’ should not be used for diagnostic measures
What is radiographic density determined by?
By the number of photons that strike the film’s emulsion layer converting silver halid crystals to metallic silver.
What does the metallic silver do?
Prevents the transmission of light through the film.
What influences the radiographic density?
mA
kVp
exposure time
focal spot to film distance
subject density
subject thickness
What is a grid?
Lead strips staggered with radioluscent material
* Helps filter x-rays through to expose the cassette
* incorporated in the cassette case or separate screen
** REDUCES SCATTER (compton, coherent) - reduces fog on radiograph **
what steps are involved in processing an x-ray film?
- Developer
- Wash
- Fixer
- Wash
- Dry
What occures to the film when exposed to the developer?
Converts chemically changed (altered) silver halide crystals into metallic silver grains that cover the film.
What happens during the was steps?
rinse for 30 sec
removes developer or fixer
What happens when exposing the film to fixer?
Removes undeveloped silver halid crystals.
Hardens and shrinks the emulsion layer
When an xray is emitted from the source of radiation it will pass through material or get absorbed by material (radiolucent - radiopaque). The xrays that pass through the material strike the emulsion layer of the film and alter the structure of the silver halide crystal. Where the xrays were absorbed in the material the silver halid crystals remain unchanged. When developing the changed silver halide crystals will be converted into silver metalic grains that remain on the film - the creates the darkness on the image. The unchanged silver halide crystals will be washed off during fixation and the fill will be lighter colored in that region.
Does the metalic silver grains create the dark or light portion of the image?
Dark
Why is the safelight a infared light?
low energy - will take a long time to actually convert a silver halid crystal
For every _____ degrees celsius icreas in temperature the rate of reaction ________?
10
doubles
What are the advantages of manual processing?
Most economical
Produces the best radiographs
What are the disadvantages of manual processing?
Most time consuming
What are the advantages of automatic processing?
Most efficieent film processings
Faster than manual
Produces dry films
What are the disadvantages of autmatic flim processing?
Expensive
Do you drain the chemicals down the drain?
NO!
Recyle