Production of X-Rays

what is domestic electricity supply

22/240 volts

50 hertz

13 amp current

circuits can be fused at 3 5 or 13

what is the structure of an atom

nucleus - positive charge proton and neutral neutrons

electrons - negative and orbiting the nucelus

what is a cathode filament

fine wire made of tungsten

small current passed along it eg 8-10mA

electrons are excited

witre gets hot and can give off light

electrons are lost from outer shell/orbit round the nucelys

electron cloud forms around the cathode

what is an anode

small tungsten target embedded in copper

large potential difference between anode and cathode eg 70kV

-ve elcetrons bombard +ve anode

high energy electrons come to sudden stop or decelerate and energy form changes

99% heat 1% rays

what is xray producing collisions

2 types of xray spectra;

continuous - bremsstrahlung or breaking radiation

has wide range if photon energy

characteristic -

depends on material in anode

emitted by loss of electrons from K and L shells

what is continous spectrum

wide range of photon energies

small defelctions are most common - many low energy photons

little penetrating power - need filtering out

large deflections less likely - few high energy photons

max photon energy directly relayed to kV across xray tube

what is characteristic spectrum

characteristic of anode atom - tungsten

line spectra relating to K and L shells

K lines of diagnsotic importance w photon energy lebels 58-69.5kV

L lines are less than 10kV

xray needs to be operating bove 69.5kV

what is scattering

random change in direction after hitting something

what is absorption

deposition of energy into the tissues

what is intesntity

number of xray phtons in a defined area of the beam

what is attenuation

reduction in intensity of beam due to scattering and absorption

what is ionisation

removal of electron from neutral atom to give -ve electrons +ve atom ions

what is penetration

ability of photons to pass through or into tissues

what is xray interactions

completely scattered with no loss of energy

absorbed w total loss of energy

scattered with some absorption and loss of energy

transmitted unchanged

what are the properties of xrays

travel in straight lines in free space

xray photons form a divergent beam

penetrate matter

can be absorbed and scattered

not detectable by human senses

produces latent images on film emulsion

xauses ionisation

can cause biological damage

cause certain salts to flurosce and emit light

what is radiation dose

amount of radiation absorbed by pt

low energy photons often are absorbed by soft tissues

what are the properties of electromagnetic radiation

dividing into ionising and non ionising radiation

properties depend on wavelength

some properties are harmful to living tissues

biological harm is not limited to ionising radiation