5. The x-ray tube (P1) Flashcards
What movement does a floor mounted x ray support system do?
Limited:
-Vertical
-Transverse
-Longitudinal
What is a C/U arm system used for?
IV radiography suites
What 4 types of protection does the protective housing provide?
- Radiation protection
- Electrical protection
- Thermal protection
- Physical protection
What type of physical protection is in the x ray tube
Lead lined except for window
What type of electrical protection is used in the x-ray tube?
-High V receptacles
-Tube made of glass
-Oil
Why is it beneficial to have the tube made of glass and filled with oil?
It doesn’t transmit current and oil moves heat away
What thermal protection is used in the tube?
Oil-moves the heat away by absorbing it
Cooling fan
What type of glass is the tube made of and why is it beneficial?
Pyrex:
-It has a VERY high heat capacity
-Is an insulator
When would you use a metal tube?
When you use high techniques like CT
What are the benefits to a metal tube?
-Tungsten does not build up
-You can control the potential
-Less tube wear, higher lifespan
What are the two filaments used for?
-Small focal spot size
-Large focal spot size
What is the benefits of a tungsten coil around the filaments?
-Has a high melting point (prevents wire from melting)
-Has a low vapour pressure
What is the filament?
The source of electrons
Explain thermionic emission in an x ray tube:
- Current makes heat (2200 C) in the tungsten wire
- Heat gives more energy to e-
- Electrons escape conduction band forces (essentially burned off wire and travel)
What is space charge?
It is when e- form a cloud around the filament (+) when you have your finger halfway down on the exposure button
When you select a high kVp, what happens to the filament heating current and the space charge size? What would happen with low kVp?
High kVp:
It decreases as its easier to pull mA across tube
Low kVp:
It increases
What are compensation circuits?
IT is a space charge compensating circuit that ensures mA is what we choose
What is the difference between filament current and tube current?
Filament current: Creates a space charge/during prep button, measured in A
Tube current: Allows the mA to flow across the tube/during exposure button, measured in mA
