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RAD Ch. 5 Vocab
Question | Answer |
---|---|
Filament | A coil of tungsten wire that is the source of electrons for x-ray production. |
Space charge | An area, filled with electrons created by thermionic emission, that are available for x-ray production. |
Target | A hard, smooth, slanted metal surface that is bombarded with fast moving electrons |
Thermionic emission | An electron cloud formed when electrons in the outermost shells get so far from the nucleus that they are no longer held in orbit. |
Electron stream | Fast moving electrons from the cathode to the anode. |
Bremsstrahlung | An x-ray photon formed by a change in kinetic energy as an incoming electron changes direction when it nears the nucleus of a target atom. |
Heterogeneous | Made up of many different wavelengths |
Characteristic radiation | An x-ray photon formed by the collision of an incoming electron with an inner shell electron. |
Focusing cup | A hollow area on the cathode containing the filament. |
Dual-focus | Having two filaments, one small and one large. |
Focal spot | The area on the target that is struck by the electron stream during the exposure. |
Rotating Anode | A spinning disc, coated with tungsten on the beveled edge, that is struck by the electron stream during the exposure. |
Target angle | The slant of the anode surface. |
Focal track | The tungsten focal area all around the beveled edge of the rotating anode. |
Effective focal spot | The vertical projection of the electron stream. Influences image sharpness. |
Actual focal spot | An area on the target surface that is struck by the electron stream. |
Line focus principle | The result of the electron stream striking an angled target and thus becoming smaller. The steeper the target angle, the greater the difference in size. |
Anode Heel Effect | The uneven distribution of radiation intensity. Greatest toward the cathode side of the tube. |
Filtration | The process of removing the long-wavelength photons from the x-ray beam. |
Kilovolts peak (kVp) | The unit used to measure voltage across the x-ray tube. |
Milliampere-seconds (mAs) | The unit used to indicate the quantity of exposure. The product of mA and exposure time. |
Tungsten (W) | A metal element; a large atom with 74 electrons in orbit around its nucleus. |
Millisecond (msec) | A small unit of measurement. One of these equals 0.001 seconds. |
Exposure time | The length of time that the x-rays are turned on. |