ANSWERS

1. Why does bone appear whiter on a radiograph than fat?
   Bone possesses a higher atomic number and higher specific gravity than fat, thus enabling the absorption of more x-ray photons resulting in a whiter image.
2. What are very dark shades on a radiograph likely to show?
   Gas.
3. Why might a very thick area of tissue appear more radiopaque than a thin area of bone?
   Thicker areas of tissue are able to absorb more x-ray photons than thin areas and therefore these may appear whiter even though you would generally expect to see darker shades.
4. What colour/s are unexposed radiographic films?
   Green, fawn or mauve when examined in daylight.
5. The film is coated with an emulsion responsible for the production of the image. What does this emulsion consist of?
   Silver bromide suspended in gelatin (with some silver iodide).
6. What attaches the emulsion layers to the transparent, polyester film base?
   A sticky subbing layer.
7. What are the outer surfaces of the emulsion protected with?
   The supercoat.
8. What is the main active ingredient in developer?
   Phenidone-hydroquinone or metol-hydroquinone
9. List 3 other chemical agents present in developer.
   • Accelerator.
   • Buffer - maintains alkalinity of the solution.
   • Restrainer - reduces development fog.
10. During the development stage of processing, the silver bromide crystals of the film emulsion are converted into black metallic silver, whilst the bromide ions are released into solution. What is the name of this reaction?
    Reduction.
11. What precautions may help arrest oxidation of the developer?
    • Keeping the developing tank covered.
    • Storing unused solution in the dark.
12. How frequently should developer be changed completely?
    Every 3 months, or when an equal volume of replenisher has been used (which ever is sooner).
13. What is the main active ingredient in fixer?
    Sodium thiosulphate or ammonium thiosulphate.
14. Is fixer acidic or alkaline?
    Acidic.
15. Describe the reaction undergone during fixing.
    The unexposed silver halide crystals are removed leaving a metallic silver image that may be viewed in normal light. Fixing renders the image permanent and insensitive to white light.
16. What name is given to describe the time taken for the removal of unexposed halide?
    Clearing time.
17. What is the term that describes the hardening of film emulsion during fixing?
    Tanning.
18. When should the fixing solution be changed completely?
    When the clearing time has doubled.
19. What colour should the dark-room walls be painted and why?
    Cream, in order to reflect the subdued lighting provided by the safe-light.
20. What is the maximum wattage suitable for a safe-light bulb?
    25 watts.
21. What colour safe-light filter should be used for blue light sensitive film?
    Brown or amber.
22. What colour safe-light filter should be used for green light sensitive film?
    Red.
23. At what temperature should manual developer be maintained?
    20° C.
24. At what temperature should automatic developer be maintained?
    28° C.
25. List 4 faults associated with poor handling of film during processing.
    • Finger prints.
    • Emulsion damage.
    • Static marks (look like forked lightning).
    • Crimp marks.
26. List 2 faults associated with the mishandling of x-ray cassettes.
    • Light leaks.
    • Dirt, dust or hair on the intensifying screens.
27. What is dichroic fog?
    Yellow stained films caused by insufficient rinsing or exhausted developer.
28. What colour will developer and fixer splashes appear on an exposed film?
    • Developer splashes - black.
    • Fixer splashes - white.
29. List 4 common environmental problems associated with processing.
    • Dirty or insufficient developer, fixer and wash water.
    • Light leaks in the dark-room.
    • Safe-light fogging.
    • Dusty drying environment.
30. List 4 advantages of automatic processing over manual development.
    • Speed.
    • Cleanliness.
    • Consistently high standard processing.
    • Solutions pumped in afresh for each film at a predetermined rate, thus minimising the risk of exhausted chemicals.
31. List 4 factors that may cause a radiograph to appear too dark.
    • Over-exposure.
    • Gross over-development.
    • Temperature of developer too high (also causing gross over-development).
    • Fogging.
32. List 4 factors that may cause a radiograph to appear too pale.
    • Under-exposure.
    • Under-development.
    • Temperature of developer too low (also causing under-development).
    • Too dilute or exhausted developer.
33. What are the 3 key terms used in the assessment of radiographic quality?
    • Contrast - difference between shades.
    • Definition - clarity of visible structures.
    • Density - degree of blackness/opacity.
34. Under-development is the most common processing fault. How might this be prevented?
    • Top up developer with replenishing solution as opposed to water.
    • Change the entire developer every 3 months.
    • Ensure that the developer is well maintained at the correct temperature.
    • Mix the developer well prior to use.
35. What is meant by a "soot and whitewash" film?
    A high contrast radiograph showing a white image on a black background with few intermediate shades. The cause is insufficient penetrating power, therefore the kV should be increased for subsequent radiographs.
36. What is meant by a "flat" film?
    A low contrast radiograph showing mainly shades of grey. The cause is usually under-development, but may occur as a result of fogging, or too high a kV.