2. OUT LINE
• Introduction
• Structure of a radiographic film
• Types and sizes of radiographic films
• Latent image formation
• Film processing
• Factors affecting film processing
• Artifacts
• Conclusion
• References
3. INTRODUCTION
• A radiographic film is use to capture and decode information carried
by the x ray beam after passing through the body.
• Direct exposure of film will require very large patient x-ray doses.
• X-rays are there fore converted to light by the intensifying screen
which then exposes the x-ray film.
• The film needs to be processed
6. STRUCTURE OF A RADIOGRAPHIC FILM
• Film base: typically 0.2mm thick
• Adhesive layer
• Emulsion: 5-10 micro meter
• Super coating
7. Film base:
• Main function is to provide support for the fragile photographic
emulsion.
• it must not produce a visible pattern or absorb too much light when
the radiograph is viewed.
• The flexibility, thickness and strength of the base must allow for ease
of processing and produce a radiograph that feels right when
handled.
8. Types of film base
• Glass plate.
• Cellulose nitrate.
• Cellulose triacetate.
• polyester; improved dimensional stability and much stronger.
• Blue tint: easier to look at and less eye strain.
9. Emulsion:
• Coated on both sides of the base.
• Composed of silver halide suspended in the gelatin.
• Gelatin
• Silver halide: AgBr - 90%, AgI - 10% in form of crystals or grains. Each
containing about 1M to 10M silver ions.
• Silver sulfide usually located on the surface of the crystal serves as
the sensitivity speck that traps electrons to begin formation of the
latent image centers.
13. • Clumps of the silver atoms are termed latent image centers, and are
the sites at which the developing process will cause visible amount of
metallic silver to be deposited.
• At least two atoms of silver must be present at a latent image center
to make a grain developable.
14. Super coating
• Thin layer made commonly of gelatin.
• Protect the emulsion from mechanical damage.
15. Direct x-ray exposure:
• Effect is caused by the electrons emitted from photoelectric
absorption or Compton scattering.
• The manner in which the energy is of these electrons is imparted to
the photographic emulsion is complex.
• The final result is the freeing of electrons from the bromide ion,
producing bromine atom and an electron that can move to the
trapping site.
16. • Most of the energy of the absorbed photon is lost esp. to the gelatin.
• Only 3 to 10% is used to produce silver.
• Sensitivity varies significantly with the KVp of the x-ray beam.
17. TYPES OF X-RAY FILM
• Types of x-ray film:
1. Based on coating
• Single emulsion film e.g. In mammography.
• Double emulsion e.g. in conventional radiography
2. Based on sensitivity
• Ortho-chromatic: Blue sensitive films e.g. conventional films and
green sensitive films.
• Poly or panchromatic
18. 3. Based on use of screen
• Non screen type e.g. dental films
• Screen type
a. Single screen
b. Double screen
19. Film sizes:
• 10 x 8 inch (18 x 24 cm)
• 12 x 10 “ ( 24 x 30 cm)
• 12 x 15 “ (30 x 40 cm)
• 14 x 14 “ (35 x 35 cm)
• 14 x 17 “ (35 x 43 cm)
21. Types of processing
Manual and automatic
1. Manual:
• The film is processed manually.
The developer, rinser, fixer and
washer are put in separate
compartments.
• The film is then dried using a
drier.
23. 2. Automatic:
• Film is processed using an
automatic film processor.
• The film is fed into the input
chute of the processor and
shuttled in to the developer,
fixer, wash tank and then dried.
24. OTHER TYPES OF PROCESSING
• Rapid processing:
• The normal time it takes to develop a film is about 90secs.
• In rapid processing, the time is reduced to 45secs.
• Usually occurs in emergency settings.
• Temperature is raised to 30degC or concentration of the developer
increase.
Extended processing:
• The development time is increased to about 120secs.
• Usually used in mammography it reduces radiation to the patient.
25. DEVELOPEMENT
Development:
• A chemical process that amplifies the latent image by a factor of
millions to form visible silver pattern.
• The basic reaction is reduction of the silver ion to black metallic silver.
• The developer is the reducing agent.
• Initiated at the latent image speck.
• The role of the silver atoms in the in the latent image is to catalyze
the reduction of the silver ions in the grains by the developing
chemicals.
26. • The silver in a grain that does not contain a latent image can be
reduced by the developer but at a much slower rate.
• Development should be discontinued when the differential between
exposed developed grains and unexposed undeveloped grains is at
maximum.
27. Constituents of a developing solution:
1. The developing agents - Hydroquinone with either phenidone or
metol.
2. An alkali- to adjust the pH
3. Preservatives- sodium sulfite
4. Restrainers, or antifogants.
28.
29. Alkali:
• Adjust the pH which affects the developing power of the agent.
• Serves as a buffer to control the hydrogen ions liberated.
• Typical alkalis used include; sodium hydroxide and sodium carbonate.
30. Sodium sulfite:
Serves two functions
1. Preservative; it decrease the rate of oxidation of the developing
agents esp. hydroquinone
2. It reacts with the oxidation products of the developing agents to
form colorless soluble sulfonates.
32. Rinsing:
• The film is rinsed to remove the developing solution before
proceeding to the fixing solution.
33. • Fixing:
• The process through which the undeveloped silver halide in the
emulsion is removed.
• The solubility of the silver halide in solution is controlled by the
concentration of the silver and halide ions.
• Silver bromide is only slightly soluble in water
• Silver ion x bromide ion = constant
• The function of the fixing agent is to form water soluble complexes in
which silver ions are tightly bound.
34. • Agent used is thiosulfate ( sodium or ammonium).
Silver bromide + sodium thiosulfate > silver thiosulfate + sodium Br
• Hardener in the solution hardens the gelatin, reduces its swelling
making it tougher and more resistant to abrasion.
35. Washing:
• Serves to remove the fixing chemicals.
• In incomplete washing, the retained sodium thiosulfate will react with
the silver image to form brown silver sulfide causing the x-ray film to
turn brown.
• Tap water is used as the washing medium.
36. • Drying:
• All the surface water and most of that retained in the emulsion is
removed.
• Dry air with low humidity is used.
37. • Replenishment:
• To maintain the concentration of the developing agent, preservative
and bromine and pH at constant level.
• Replenishment solution is free of bromide, contains alkaline agents
and buffers and the depleted preservatives and developing agents.
38. • Silver recovery:
• Silver is a toxic heavy metal and the final processed film contains only
about half the silver contained in the original emulsion.
• The silver is removed from the fixer solution by the electrolytic
recovery system attached to the waste line of the fixer tank.
• The recovered silver can then be sold to the commercial companies.
39. Factors affecting film processing
1. Film density
A. Increased film density
Too long time in the developer.
High temperature of processing solution.
Incorrectly mixed developer.
B. Decrease film density.
Too short time in the developer.
Low temperature of processing solution.
Exhausted developer.
40. 3. Fogging
Age fogging: use of very old film
Safe light fogging: unmatched safe light to the film is used.
Chemical fogging: prolong stay in the developer, high temperature,
faulty composition, contamination.
41. Ideal conditions for film processing
• Temperature: 18-20 degC.
• Humidity: 40-60%.
• Safety light: film is designed to be insensitive to specific wave lengths
of the light spectrum.
42. ARTIFACTS
• An artifact is any unwanted density not representing the patient’s
anatomy.
• Presents in a variety of ways including abnormal shadows or
degraded image quality.
43. Sources of artefacts
• Patient.
• During radiographic exposure.
• During film processing.
• When the film is being handled.
45. Exposure artifacts
Associated with the manner in which the radiographer conducts the
examination.
Poor screen film contact.
Improper positioning of the patient and collimation.
Patient motion.
Double exposure.
46. • Processing artifacts:
Occurs during processing of the radiographic film.
Chemical spots – occur if any chemical splashed or transferred by
wet fingers to the undeveloped film.
Dark spots – indicates either water or developer on the film before
processing
Light or undeveloped spots indicates fixer on the film before
processing.
57. CONCLUSION
• Film-screen radiography and film processing provides the basis of
radiography.
• Although largely replaced by digital radiography, they are essential
tools that should be learnt and understood well since they are still
being used in many centers.
58. REFERENCES
• Thomas S. Currey, James E. Dowdey, Robert C. Murray JR, “Christensen’s
Physics of diagnostic imaging”, 4th edition, 1990, ISBN 0-8121-1310-1.
• Jerrold T,J.Anthony, The Essential Physics of Medical Imaging.
• Radiopedia.org- accessed several times.
• Radiology assistant.org- accessed several times.
