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Radiology
Chapter 3 Vocab
Term | Definition |
---|---|
Alternating Current | a flow of electrons in one direction, followed by a flow of electrons in the opposite direction. |
Anode | the positive electrode in the x-ray tube. |
Cathode | The negative electrode in the x-ray tube. |
Central Ray | The central portion of the primary beam of radiation. |
Collimator | A diaphragm, usually lead, designed to restrict the dimensions of the useful beam. |
Dead-man switch | A switch so constructed that a circuit closing contact can only be maintained by continuous pressure by the operator. |
Direct Current | electric current that flows continuously in one direction. Ideal for use with digital imaging. |
Electron Cloud | a mass of free electrons that hovers around the filament wire of the cathode when it is heated to incandescence. The number of free electrons increases as the milliamperage is increased. |
Exposure Button | Keypad or switch that activates the x-ray production process. |
Filament | the spiral tungsten coil in the focusing cup of the cathode of the x-ay tube. |
Filter | absorbing material, usually aluminum, placed in the path of the beam of radiation to remove a high percentage or the low energy x-rays. |
Focal Spot | small area on the target on the anode toward which the electrons from the focusing cup of the cathode are directed. X-rays originate at the focal spot. |
Focusing Cup | A curved device around the cathode wire filament that is designed to focus the free electrons toward the tungsten target of the anode. |
Impulse | measure of exposure time 60/second |
Intensity | The total energy of the x-ray beam. The product of the number of x-rays and energy of each x-ray per unit of area per time of exposure. |
Kilovolt Peak | the crest value in kilovolts of the potential difference of a pulsating generator. |
Milliamperage | one thousandth of an ampere. Milliamperage determines the number of electrons available at the filament. |
Primary Beam | The original undeflected useful beam of radiation that emanates at the focal spot of the x-ray tube and emerges through the aperture of the tube head. |
Quality | Term used when describing the intensity of the x-ray beam. Refers to the energy strength or penetrating ability of the x-ray beam. |
Quantity | Refers to the number of x-rays in the beam. |
Target | Small block of tungsten imbedded in the face of the anode; bombarded by the electrons streaming from the cathode. The focal spot is located on the target. |
Thermionic Emission | The release of electrons when a material is heated to incandescence. Electrons in the x-ray tube when electric current is passed through. |
Tube Head | Protective metal covering that contains the x-ray tube, the high voltage and low voltage transformers and insulating oil. Attached to the flexible extensions arm by a yoke. The PID attaches to the tube head at the port. |
Tungsten | Element with an atomic number of 74. High melting point makes this metal ideal for use as the cathode filament and as the anode target. |
X-ray Tube | Electronic tube located in the tube head that generates x-rays. |