Production Of Xrays Flashcards
What components make up the tube head?
Filament cathode ( tungsten) Copper block Target anode ( tungsten) Step up transformer Step down transformer Leaded glass Led shield Oil Aluminium filter
What is the function of the cathode?
Provides source of electrons
What is the function of the copper block?
Removes and dissipates heat
What does the step up transformer do?
Send high kv across tube
What does the step down transformer do?
Creates low filament milli amp
What does the lead shield do?
Minimises radiation leakage
What does the oil do?
Facilitates heat removal
What does the aluminium filter do?
Removes low energy, damaging X-ray photons
What are the two types of xray spectra?
Continuous spectrum ( bremsstraulung/ breaking radiation) Characteristic spectrum
What is meant by continuous spectrum?
X-ray photons emitted by rapid deceleration of bombarding electrons passing close to nucleus in tungsten atom
What is meant by characteristic spectrum?
Depends on material used in anode
Emitted by loss of electrons from k and l shells
What are the main properties of xrays?
Travel in straight lines X-ray photons for divergent beam Can travel through vacuum Can be absorbed Can be scattered
What come under non ionising with regards to electro magnetic spectrum
Radio
Microwaves
Infrared
Low end ultra violet
What come under ionising with regards to the electro magnetic spectrum
High end ultraviolet
Xrays
Gamma rays
Define scattering
Random change in direction after hitting something
Define absorption
Deposition of energy in tissues
Define intensity
Number of X-ray photons in a defined area of a beam
Define attenuation
Reduction in intensity of beam due to scattering and absorption
Define ionisation
Removal of electrons from neutral atom to give negative electron and positive atom ions
Define penetration
Ability of photons to pass through tissues/ materials
What are the possible interactions of X-ray beams?
Completely scattered with no loss of energy
Absorbed with total loss of energy
Scattered with some absorption and loss of energy
Transmitted unchanged
What are the possible interactions of xrays at atomic level
Rayleigh scattering- pure scatter
Photoelectric effect- pure absorption
Compton effect- absorption and scatter
Pair production - pure absorption
What is the photoelectric effect?
Pure absorption predominating with low energy protons
Describe the stages of photoelectric
Incoming xrays interact with k electrons
Electron ejected with much energy
X-ray photons looses all energy and disappears
Vacancy exists in inner shell and is filled by outer shell electrons
Excess energy emitted as light or low energy xrays
Atomic stability and neutral state
What is the Compton effect?
Absorption and scattering process predominating with higher energy photons
Describe the stages of Compton effect
Incoming xray photon interacts with outer shell electron
Electron injected with some energy from X-ray
Electron now called Compton recoil electron
Remaining photon energy scattered
Escapes from tissues into environment
What are the main components of the tube head?
Tube head Collimator Positioning arms Control panel Circuitry
