X-ray Image processing Flashcards
List down the stages involved in the chemical processing of radiographic images.
- Development
- Fixing
- Washing
- Drying
Development
- The primary purpose is to convert a latent image into a visible image.
- Exposed Silver halide grains in the emulsion layer are reduced to metallic silver. while the unexposed remain unchanged.
By products of the development
- AgH is reduced to Ag on continuous development process, causing depletion of electrons in the developer.
- Reaction of developer and atm O2 causes aerial oxidation in developer.
- The Br ions react with hydrogen ions to form hydrobromic acid. which causes the pH to fall
Developing agents:
These chemicals, like hydroquinone [C6H4(OH)2] and phenidone[C9H10N2O], are responsible for reducing silver bromide crystals
Alkali/ accelerators (e.g., sodium carbonate):
This maintains the developer’s pH level (around 10-11) for optimal activity
Preservative (e.g., sodium sulfite):
This slows down the oxidation of the developer, extending its life.
Replenisher
A solution that contains the same components as the developer but more concentrated is added to the developer tank to maintain its activity and image quality.
Restrainer (e.g., potassium bromide):
This controls the developer’s activity, preventing it from reacting with unexposed silver bromide (which would cause fogging on the film).
Define development
- A process of chemical reduction achieved by the developer donating electrons to Ag ions in the exposed AgH grains and converting them to metallic silver.
Constituents of the developer solution
- solvent
- Developing agents
- Accelerator
- Buffer
- Restrainer
- Preservatives
- Hardener
- sequestering agents
Starter Solution (sometimes referred to as “restrainer bath”):
This solution is sometimes used before the developer, particularly in manual processing. It is essentially a dilute solution containing only the restrainer.
Buffers
A chemical compound that maintains the pH of a solution within its limits.
Hardeners in the developer
Glutaraldehyde ( organic hardener
what can happen if the hardener is not present in the solution.
there might be swelling on the emulsion layer, which can cause unsuccessful transport of the film.
Sequestering agents
chemicals that prevent precipitation of insoluble mineral salts that tend to occur in hard water areas.
Factors that affecting development.
- pH of developer solution
- Concentration of developing agents
- Temperature of the developer
- Development time
Fixation
- Removal of unexposed silver halide crystals
- Hardening the emulsion
- Stopping development
- clearing the image
- Stopping the development
The fixer can slightly raise the pH of the solution, which helps to stop the developer’s activity and prevent further development of the image.
- Removal of unexposed silver halide crystals
The fixing solution, typically containing sodium thiosulfate, dissolves the unexposed silver halide crystals. This is because the fixer forms a soluble complex with the silver ions present in these unexposed crystals, allowing them to be washed away.
- Hardening of the emulsion
During development, the developer can slightly soften the emulsion.
The fixing solution often contains additional hardening agents that help to counteract the softening effect of the developer and make the emulsion more durable. aluminum sulfite.
The constituents of fixer replenisher solution.
*Solvent
*Fixing agent
*Acid
*Hardener
*Buffer
*Preservative
*Anti-sludging agent
Solvent
water
dichroic fog
a specific type of fog that occurs during development process whereby a thin l layer of metallic silver is redeposited unto the film. the layer may appear red or green.
buffer
Important in controlling pH in order to:
a. Prevent sulphurization;
b. Ensure neutralization of developer; and
c. Maintain optimum hardener activity.
sodium acetate
anti-sludging agent
Due to the tendency of Al salts used as hardeners producing insoluble Al compounds which may precipitate out to form a sludge and adheres to films and sides of fixing tank, anti-sludging agents are added to reduce formation of the sludge
Factors affecting fixation
*Constitution of the fixing solution
*Fixer temperature
*Fixing time
- Washing
- Dissolved salts can crystallize so they have to e washed.
- To prevent gradual development of yellow-brown stain caused by silver complexes and ammonium halides.
