Saved Bookmarks
| 1. |
Regarding the crystal used in gamma cameras: a. It is usually made of NaI due to its robust qualities b. It absorbs gamma rays mainly by photoelectric absorption c. The absorption of a single gamma proton results in the production of a single light photon d. Using a thicker crystal improves intrinsic resolution e. A crack in the crystal results in a linear defect on a uniform background |
|
Answer» a. False. The crystal used in gamma cameras is usually made up of NaI but is fragile and can be damaged by both water and heat. b. True. As a result of photoelectric absorption, the crystal absorbs the majority of gamma rays from Tc-99m. c. False. The absorption of a single gamma photon produces thousands of light photons, which spread out in all directions. d. False. Using a thicker crystal improves sensitivity but reduces intrinsic resolution. e. True. A sheet phantom (filled with Co-57) is used to test the detector, which should give a uniform response to a uniform field. A defective photo multiplier is seen as reduced counts, and a cracked crystal shows a linear defect. |
|