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X Ray Tube 147
Part 1
| Question | Answer |
|---|---|
| Conditions necessary to produce x-rays | Source of electrons, Appropriate target materials, High voltage, Vacuum |
| Protective Housing is a _______ | Cast steel structure lined with lead |
| The X-Ray Tube is contained in the | Protective Housing |
| GLASS OR METAL ENCLOSURES Primary Function | maintain the vacuum to allow the electrons to travel from cathode to anode with minimal to no attenuation by air or gas molecules |
| Source of electrons | Cathode |
| Way to stop electrons abruptly | Anode |
| Area of enclosure x-rays emitted thru | Window |
| The Window is the | Thinnest area of enclosure |
| Cathode Function | Produce the thermionic cloud & focus electrons toward the anode |
| Cloud size depends on ____ selected | mA |
| Electrons form an _____ or space charge | Electron Cloud |
| The cloud is driven toward the _____ on exposure | Anode |
| The Space Charge Effect | Negative charges formed repel one another. Limits number of electrons emitted |
| Cathode has | Two Filaments |
| Excessive holding of rotor switch can cause | Premature Tube Failure and Shorten tube lifespan |
| General purpose x-ray tubes will not exceed | 1000 mA (2000 mA in special tubes) |
| Cathode is the _______ side of the x-ray tube | Negative |
| Metal cover with filaments embedded in shallow depression (made of nickel) | Focusing Cup |
| Focusing Cup Purpose | Narrow the thermionic cloud & direct electrons toward the anode |
| The Anode is the _______ side of the x-ray tube | Positive |
| What is the target metal of choice? | Tungsten |
| Anode Functions | Electrical conductor, Thermal conductor • Target area support |
| Mammography target material of choice | Molybdenum |
| Mixed with target materials to create an metal alloy – Strengthens target materials | Rhenium and Rhodium |
| Tungsten-rhenium alloy (90% Tungsten 10% Rhenium) is used in | X-Ray |
| Molybdenum – rhodium alloy is used in | Mammography |
| _______ Dissipate heat quickly | Graphite and Copper |
| Fixed target used in dental imaging & imaging that does not require high tube currents | Stationary Anode |
| _______ is powered by an induction motor | Anode Rotation |
| Entire surface = target area Heat spread over a wider area and dissipate quickly | Rotating Anode |
| A rotating anode is bombarded by electrons for only | 7-50 microseconds |
| A rotating anode spins at ______ in general purpose tubes | 3, 400 – 3,600 rpm (10,000 rpm in high capacity tubes) |
| General x-ray tubes composition: | Pyrex Glass |
| Electrons “boil off” when heated (2200o C) | Thermionic Emission |
| The Stator is located _______ the metal or glass enclosure/envelope | Outside |
| The Rotor is located ______ the glass envelope | Inside |
| _______ make excessive exposures repeatedly (This can damage the X-Ray Machine) | DO NOT |
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