Introduction Flashcards
ionization
electron is removed –> ion pair
ionizing radiation sources
cosmic, radon, imaging
radon gas
largest source of natural radiation
x-ray discovery
- 11/9/95, Wilhelm Roentgen
x-ray properties
- penetrability
- ionizating
- fluoresce and emit light
imaging system components
- tube
- operating console
- high-V generator
x-rays are emitted..
isotropically (all directions)
cathode
- negative end
- thoriated tungsten –> heat resistant filament
thermionic emission
filament temp rises until outer shell electrons “boil off”
focusing cup
(-) charged and confines accelerated electrons toward anode
anode
- (+)
- target (conductor)
- dissipates heat
rotating anodes
reduced heat damage to tube
disadvantage of line-focus principle
anode heel-effect: electrons interact with target at various depths
uniform tissue exposure
anode must face thinner body part
Will the grid reduce extrafocal radiation?
NO
x-ray (high voltage) generator
modifies incomig voltage and current
control panel
technical factors (mA, kV, Time)
transformer
modifies voltage
step-up transformer
V increase and I decreases for greater beam energy
step-down transformer
V decrease and I increase to heat cathode for thermionic emission
rectifiers
AC –> DC
high-frequency power generator
provides constant potential V waveform which doubles radiation
collimator
restricts x-ray to target area
added filtration
aluminum filters to harden beam and improve penetrability and lessen scatter radiation