QUESTIONS

1. What is the output of most portable x-ray machines?
2. What is the maximum output of most mobile x-ray machines?
3. What is the maximum output of most fixed x-ray machines?
4. What is the purpose of the line voltage compensator?
5. Larger x-ray machines may possess a device which automatically controls electrical fluctuations; what is this device called?
6. What is the minimum distance away from the tube head that the exposure button may be situated?
7. What is the function of the kilovoltage (kV) control?
8. What is another term for the kilovoltage applied across the tube?
9. When would it be sensible to select a high kV setting?
10. What is the function of the milliamperage (mA) control?
11. What is the milliamperage also known as?
12. What unit denotes the product of the tube current (mA) and the length of exposure?
13. In small x-ray machines, the kV may be directly linked to the mA. Why might this be disadvantageous?
14. If the tube current (mA) is increased, how is the exposure time (mAs) affected?
15. Why is it sensible to use the largest possible mA for a particular kV setting?
16. If the kV were increased by 10, by how much would you need to reduce the mAs in order to produce a film of similar diagnostic quality to the exposures used initially?
17. What is meant by the film focal distance (FFD)?
18. State the inverse square law.
19. What is a suitable FFD for most portable x-ray machines?
20. In addition to FFD, what other parameters must be kept constant when calculating exposures?
21. What device is used for measuring the depth of tissues?
22. What is the purpose of a grid?
23. How does a grid work?
24. List the 4 main types of stationary grid.
25. What is the name of the expensive, but very efficient moving grid which is built into the radiography table-top?
26. Why is a focussed grid preferable to a parallel grid?
27. What important factors must be taken into account when a grid is used?
28. What is meant by the "grid factor"?
29. Define grid ratio.
30. What is the main disadvantage of grid use (apart from cut off) and how might this be rectified?
31. What is the purpose of intensifying screens?
32. Where are the intensifying screens located?
33. What colour light is emitted by calcium tungstate screens?
34. What colour light is emitted by rare earth phosphor screens?
35. Why are rare earth screens preferable to those of calcium tungstate?
36. Describe how you would clean an intensifying screen.
37. What film type is suitable for use with calcium tungstate screens or blue light emitting rare earth phosphors?
38. What film type is suitable for use with green or blue light emitting rare earth phosphors?
39. When would non-screen film be utilised?
40. What is the main disadvantage of non-screen film?
41. What is the main advantage of a fast film-screen combination?
42. What is the main disadvantage of a fast film-screen combination?
43. What is the main advantage of a slow film-screen combination?
44. What is the main disadvantage of a slow film-screen combination?
45. List 6 important factors regarding the storage of unexposed radiographic film.