Ch. 5 XR Production Flashcards
- vacuum
- source of electrons (filament)
- target
- high potential difference (voltage)
Requirements for Xrays
-envelope
- filament
- target
Elements of tube housing
Pyrex glass forms the structure of the tube
Envelope
Tungsten is the source of electrons & is located on the Cathode side
Filament
Slanted metal surface that “attracts” the electrons towards the Anode side
Target
Heated electrons increase distance from the nucleus creating a space charge (“electron cloud”)
- space charge: free electrons in thr air
Thermionic emission
Electrons rapidly moving across the tube towards the target
Electron stream
Incoming electron (“pumps the breaks”) slows down & changes direction without interaction
-energy creates x-rays
Bremsstrahlung
Incoming electron knocks out k-shell electron out of orbit (“ out of character”)
-void being filled creates xray
Characteristic
Below 70 kvp = all interactions are brems
Above 70 kvp = 85% of interactions are brems, 15% are characteristic
How many interactions are bremsstrahlung or characteristic?
Is dual focus,
Contains 2 filaments (small & large) & a focusing cup
Cathode
A hollow area for the filament that has a slight neg. Charge allowing the electrons to repel towards the focal spot. (Actual vs effective)
Focusing cup
- Measures target surface
- larger in size to absorb heat generated for thicker body parts
- less image resolution
1.2mm
Actual focal spot
- Measures projection of the actual focal spot
- Affects image resolution
- produces better detail
0.6mm
Effective focal spot
Contains a rotating antode that uses electromagnetic induction to rotate for heat capacity
Anode
