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RADT334 - X-Ray Tube
Radiographic Physics Review Covering X-ray Tube
| Question | Answer |
|---|---|
| What are the external components of the x-ray tube? | Support system, protective housing, enclosure |
| What are the 3 type of support systems? | Floor to ceiling, ceiling, c-arm |
| Which support system is most frequently used? | Ceiling |
| What is the purpose of the protective housing? | Controls leakage and scatter radiation, isolates the high voltages and provides a means to cool the tube |
| What are the two types of materials used for the enclosure? | Glass or metal |
| Which type of material used for the enclosure causes a longer life for the x-ray tube? | Metal |
| What are the internal components of the x-ray tube? | Cathode and anode |
| What material is used most frequently in the filament? | Thoriated tungsten |
| What is the benefit of using thoriated tungsten in the filament? | Prolongs tube life and higher thermionic emission |
| What is the purpose of the small focal spot? | Used when better spatial resolution is required (bone work) |
| What is the purpose of the large focal spot? | When large body parts are imaged and when higher techniques are used that will generate heat |
| What is the space-charge effect? | The cloud of electrons makes it hard for subsequent electrons to be emitted because of electrostatic repulsion |
| What are the two types of anodes? | Stationary and rotating |
| When is a stationary anode used? | Dental x-ray imaging systems, some portable imaging systems, and other special-purpose units in which high tube current and power are not required |
| When is a rotating anode used? | General-purpose x-ray tubes (capable of producing high-intensity x-ray beams in a short time) |
| Why is tungsten the material of choice for the anode target? | High atomic number, thermal conductivity, high melting point |
| What is the atomic number of tungsten? | 74 |
| What is the melting point of tungsten? | 3400 degrees C |
| What is the line-focus principle? | Angled target allows for larger area for heating while maintaining a small focal spot |
| What does the line-focus principle do to radiographic images? | Improves spatial resolution and heat capacity |
| What is the anode heel effect? | The intensity of the x-ray beam on the anode side is weaker because it has a longer path through the target |
| How should positioning change to accommodate the anode heel effect? | The cathode should be over the thicker part of the anatomy to provide a more uniform exposure |
| What is the most frequent cause of tube failure? | Vaporization of the filament causing tungsten to coat the enclosure (causes arcing) |
| How can the radiographer prevent anode cracking due to rapid increase in anode temperature? | Warm the anode by low-technique operation if maximum techniques are required |
| How does bearing damage occur? | Maintaining the anode at elevated temperatures for prolonged periods |
| What does a radiographic rating chart show? | Conveys which radiographic techniques are safe and which are unsafe |
| What does an anode cooling chart show? | The thermal capacity of an anode and its heat dissipation characteristics |
Created by:
marchuleta1
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