Term
| what does isotropically mean |
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Definition
| when x-rays are produced in equal intensity in all directions |
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Term
| x-rays emitted through th window |
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Definition
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Term
| x-rays that escape through the housing |
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Definition
| leakage radiation (less than 1 mGy/hr) |
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Term
| why do some x-ray tubes have oil |
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Definition
| insulate against electric shock, dissipates heat |
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Term
| what is the purpose of the vacuum tube |
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Definition
| more efficient, longer life |
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Term
| what is the glass tube made out of |
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Definition
|
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Term
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Definition
| when tungsten evaporates and coats the inside of the tube |
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Term
| which side of the tube is negative |
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Definition
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Term
| what the 2 primary parts of the cathode |
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Definition
| the filament and the focusing cup |
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Term
| what is the filament made of |
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Definition
|
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Term
| why do we use tungsten for the filament |
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Definition
| higher thermionic emissions, high melting point |
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Term
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Definition
| a metal cup in which filament is embedded, negatively charged to confine beam to small area of anode |
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Term
| filament: a small rise in filament current results in- |
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Definition
| a large rise in tube current |
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Term
| the x-ray tube current is controlled how |
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Definition
| by controlling the filament current |
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Term
|
Definition
| the cloud of electrons surrounding the filament |
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Term
| what is the advantage of the small focal spot |
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Definition
| better spacial resolution |
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Term
| which side is the positive side |
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Definition
|
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Term
| what are the two types of anodes |
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Definition
|
|
Term
| what are the three functions of the anode |
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Definition
| electrical conductor, mechanical support for the target, thermal dissipator |
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Term
| what is the most common anode material |
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Definition
| copper, molybdenum, graphite |
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Term
| what are the three mains reasons tungsten in the target |
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Definition
| high atomic number, thermal conductivity, high melting point |
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Term
| what material gives the target added mechanical strength |
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Definition
|
|
Term
| why does the anode rotate |
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Definition
| allows beam larger area to interact with (500 times), therefore not heating the anode all in one spot |
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|
Term
| at what speed does the anode rotate |
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Definition
|
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Term
| what kind of motor powers the anode |
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Definition
| electromagnetic induction |
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Term
| what are the two parts of the electromagnetic induction motor |
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Definition
| the stator (coils) and the rotor |
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Term
|
Definition
| conducts a current that induces a magnetic field that surround the rotor |
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Term
|
Definition
| area of the target from which x-rays are emitted |
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Term
|
Definition
| the area projected onto the patient and ir |
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Term
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Definition
| results when the effective focal spot size is much less than the actual focal spot size |
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Term
| how does target angle affect effective focal spot size |
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Definition
| the smaller the angle, the small the effective focal spot size |
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|
Term
| what are the target angles in a diagnostic x-ray tube |
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Definition
|
|
Term
| what is the result of the anode heel effect |
|
Definition
| smaller effective focal spot and less radiation intensity on the anode side of the x-ray beam |
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|
Term
| how does anode/target angle effect the heel effect |
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Definition
| the smaller the angle, the larger the heel effect |
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|
Term
| what is extrafocal radiation |
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Definition
| when electrons bounce off the focal spot and land on other areas of the target |
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Term
| what is the result of extrafocal radiation |
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Definition
| extends the size of the focal spot, increases skin dose, reduces image contrast |
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Term
| what are the five types of tube failure |
|
Definition
1. anode may crack due to the temp rising too quickly
2. anode at high temps for too long
3. excessive heating of bearings damaging them
4. open filament: too hot too long vaporizing the tungsten
5. electron arcing due to vaporized tungsten |
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Term
| what are the three rating charts |
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Definition
| radiographic rating chart, anode cooling chart, housing cooling chart |
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|
Term
| radiographic rating chart |
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Definition
| which techniques are safe and unsafe for tube operation |
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Term
|
Definition
| thermal capacity of anode and heat dissipation characteristics |
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|
Term
| single-phase heat capacity equation |
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Definition
|
|
Term
| three-phase heat capacity equation |
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Definition
|
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Term
|
Definition
| looks the same as anode cooling chart and is used the exact same way |
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