 | Term | Definition |
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William Coolidge |
Invented the hot cathode X-ray tube in 1913 |
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Kilovoltage (kVp) |
Controls the penetrating power of the X-ray beam |
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Bremsstrahlung (Braking) radiation |
Produced by the sudden slowing and direction change of the electron stream as kinetic energy is converted to other energy forms |
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Characteristic radiation |
Formed within the target atoms as a result of interactions with the K-shell electrons |
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Anode |
The positive, target end of the X-Ray tube |
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Cathode |
The negative, filament end of the X-Ray tube |
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Milliamperage (mA) |
Measures the rate of current flow across the X-ray tube |
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Anode heel effect |
A phenomenon of X-ray production that results in uneven distribution within the field |
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Bremsstrahlung & Characteristic radiation |
Types of radiation produced at the anode |
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Filament |
Provides the source of electrons at one end of the tube; consists of tungsten wire |
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Tungsten wire |
A large atom in the form of coiled wire with a high melting point and where free electrons for X-ray production come from |
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Effective focal spot |
Determines the degree of angulation of the X-ray tube target; the smaller the effective focal spot, the greater the image sharpness |
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Large actual focal spot |
Yields greater tube heat capacity |
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Space charge |
An "electron cloud" surrounding a hot cathode |
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70 kVp (below) |
Level in which characteristic radiation is no longer produced |
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Thermionic emission |
The principle underlying the creation of a space charge in the X-ray tube |
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Essential elements required for X-ray production |
A target, a vacuum, an electron source, and a high potential difference |
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Milliseconds |
Measures the time when exposure time is very short |
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Milliampere-seconds (mAs) |
The unit used to indicate the quantity of exposure (mA x Time = mAs) |
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Filter |
Device for removing long wavelength radiation from the primary X-ray beam |
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High potential difference |
Required to move the electron stream rapidly across the X-ray tube |
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Focusing cup |
Houses each filament in a hollow area in the cathode; slight negative charge |
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Rotating anode |
Spins during the exposure so the heat is distributed all around the circumference of the rotating anode disk |
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Target angle |
The slant of the anode surface; affects the tube's heat capacity, the sharpness of the image and the maximum size of the X-ray beam |
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Actual focal spot |
The area on the target surface that is struck by the electron stream |
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Effective focal spot |
The vertical projection of the actual focal spot |
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Line focus principle |
The size of the effective focal spot influences image sharpness |
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Electron stream |
Formed when the high positive electrical potential at the target attracts the negatively charged electrons of the space charge |
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Focal track |
The tungsten focal area all around the beveled edge of the rotating anode |
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X-ray beam filtration |
Decreases the average wavelength of the X-ray beam, does not contribute to the image and lowers patient dose significally |
