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Bushong Ch 6
The Xray Tube
| Question | Answer |
|---|---|
| Which term refer to the primary radiation used to form the image | useful beam |
| What is the formula for calculated heat units on a 3-phase system | kVP * mAs *1.4 |
| When the filament current has risen to its maximum value because all available electrons have been used | saturation current |
| The transfer of heat by the movement of hot matter to a colder place defines: | convection |
| The positive side of the xray tube is the | anode |
| The negative side of the xray tube is the | cathode |
| The speed of the anode is calculated in rpms (rotations/revolutions per minute). Which rpms do you see when viewing various rating charts? | 3400 and 10000 |
| What materials are used in the anodes of xray tubes? | copper, graphite, molybdenum |
| What are the external components of the xray tube? | protective housing, glass or metal enclosure, support structure |
| Where is the stator located? | Just outside the glass or metal enclosure of the tube, surrounding the rotor. |
| What are causes of xray tube failure? | excessive and prolonged anode heating, high exposure on a cold anode, excessive anode temperature, tungsten vaporization due to excessive tube arcing |
| What are the functions of the anode? | electrical conductor, mechanical support, thermal dissipater |
| What material is added to the filament to increase the efficiency of thermionic emission and prolong the life of the xray tube? | thorium |
| What utilizes the angle of the anode to provide a more spacious target area and accommodate a higher heat load. | line focus principle |
| The line focus principle provides a __________ effective focal spot size | smaller |
| What is the effective focal spot? | the area on the patient to which the beam is projected |
| Which portion of the xray tube is the negatively charged metal shroud that surrounds the filament? | focusing cup |
| What are the parts of the cathode? | filament and focusing cup |
| What are the functions of the protective housing of the xray tube? | guarding against electric shock, shielding from excessive radiation exposure, mechanical support and protection |
| What does the anode angle have to do with the anode heel effect? | the smaller the angle, the greater the heel effect |
| What is the vaporization of tungsten within the tube termed | arcing |
| When electrons repel, they form a cloud around the filament making it difficult for electrons to be emitted because of electrostatic repulsion | space charge effect |
| The area on the target where electrons are emitted | focal spot |
| What is the anode heel effect | based on the angle of the target, greater intensity on the cathode side of the beam |
| What powers the rotating anode | electromagnetic induction motor |
| What is the main advantage of the induction motor | reduces "coast time" |
Created by:
lkdickson
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