X-ray Production 10047/10046 Cheat Sheet

All radiation particles have two features in common: they all have a mass and they are all subatomic particles. Since particles have a mass (and sometimes a charge) = HIGH intera­ction between radiation and matter. This is one of the reasons partic­ulate radiation is not used for medical imaging; low pentating ability (we need radiation to pass through the patient and still interact with the patient, but partic­ulate radiation have very high Linerar Energy Transfer

Alpha Paticles
> released by nuclei of unstable atoms (urani­um-238, pluton­ium­-236).
> consist of 2 protons and 2 neutrons (net positive charge: +2 --> identical to helium atom).
> high L.E.T; because of their heavy weight and high charger.
> can be stopped by a piece of paper

Beta Particles
> two types: electrons and positrons. Both orginate from an unstsbale atom and have high energy and speed
> Beta+ decay: when excess protons --> proton converts into. Position and neutrino produced.
> Beta- decay: when excess neutrons --> neturon converts into proton. Electron and antine­utrino produced (rearely used in medical imaging)
> Positrion has low atomic mass, (+1 charge). Low mass and charge = lower LET, higher penetr­ability compared to alpha particles.
> stopped by a few milimetres of aluminium

Neutrons
> bypoduct of nuclear fission or fusion.
> similar mass to proton, but no charge

They are chargless and mass-less; "­packets of energy­"
they can travel in straig­htlines through empty space/­vacuum.
they are transm­itted by electric and magentic fields oscilating at right angles to each other
travel at the speed of light (in a vacuum).
they are unafected by external magnet­ic/­ele­ctric fields
wave-p­article duality. for medical imaging, we view X-rays and Gamma rays more as a wave.
low wavenl­engths, high freque­ncies; higher freque­ncies = higher energy

X-ray Production
Created from the intera­rctions of high-speed (high KE) electrons with target (e.g. tungsten).
two types: charac­ter­sitic and bremss­thr­alung radiation*

Charac­ter­istic radiation involves the fillament electrons intera­cting with orbital electron of target atom. Created when orbital electrons are removed from their shell and outer-­shell elelctrons fill inner-­shell vacancies (usually K-Shell electrons that are ejected). To fill vacancy: potential energy is releaserd as a charac­ter­istic photon. AKA. since the binding energies differ between orbiting shells: outer-­shell electrons (low BE) fills inner-­shell vacancy (high BE). Energy released is the difference between the inner-­shell BE and outer-­shell BE.

For charac­ter­istic radiation to even occur, the incident electron (fillament electron) MUST have a HIGHER than the relevant BE.
resultant charac­ter­istic x-rays are specific to certian shell-­shell transi­tions and USUALLY do not provide sufficient energy to even leave the target atom, never mind the patient

Brems photons are produced when filament electrons miss all of the orbital electrons of the target atoms and interact with the nucleus. The attraction of the fillament electron to the nucleus causes it slow down and change direction. the resultant loss of energy is given off as a brems photon.

Unlike charac­ter­istic x-rays where very specific energies are produced, brems photons have a much larger range of energy levels. The amount of direct­ional change imposed on the incident electron dictates the amount of energy released