MOD 2 - X-rays

longer wavelength means

decreased wave energy = decreased x-ray photon energy

x-rays are

a form of electromagnetic energy that is categorized as ionizing radiation = photons

types of x-rays

• characteristics

• brems

most frequent xrays emitted from the anode

brems

characteristic x-rays

1. projectile -e knocks an inner shell -e out of orbit when photon energy>binding energy

2. which creates an -e vacancy in the atom → atom is unstable

3. to balance this instability, an -e from an outer/higher energy state/valence will drop down into the vacant space called the cascade effect

4. now to stabilize the atoms energy changes, atom releases the differential energy as a x-ray photon

5. x-ray photon = (-electron energy) + (-electron energy) THEREFORE the energy is back in balance

only what level of -e shell produces diagnostic photons

only K-shell -e as they have high binding energy = lower energy state -e

Brems x-rays

1. a projectile -e passes near to the positive nucleus as it’s attracted to it

2. this course alternation slows down the -e, thus losing energy

3. this lost energy is released in the x-ray photon form

4. this -e is either fully stopped (absorbed) or slowed and diverted

5. resulting in a wide variety of x-ray photon energies

why do brems xrays create ranging xray energy levels

electrons can lose a small or large amount of energy depending on how close an electron gets to a nucleus

the resulting photon energy in brems can range from

photon energy can reach to the same kVp energy selected (80kVp = 0-80keV)

half value layer represents

the penetration ability the x-ray beam has through differing thicknesses of different materials (objects)

increasing kVp →

increases penetration quality of x-ray beam and the quantity

how much does kVp need to increase to double the amount of photons

15%

15% decrease in kVp =

50% of intensity

doubling the mAs →

doubles the number of x-rays

halving the mA =

50% decrease of intensity

how does target material influence x-rays

higher atomic number = better x-ray beam quality as it has higher probability of interactions with the electrons

good target material

gold (but low heat capacity) > tungsten

how does filtration influence x-rays

improves the overall penetration of the x-ray beam/ beam quality BY filtering out the low energy x-rays.

low energy x-rays

don’t contribute to beam quality but just increases PT dose

how does generator influence x-rays

high frequency generators → increase x-ray photon quantity