What happens when x rays hit you or the patient

Question 1

4 Types of interactions

Answer 1

1. transmitted unchanged
2. scatter and absorption - loss of energy
3. pure scatter - no loss of energy
4. absorbed - photon disappears

Question 2

Absorption - photoelectric effect

Answer 2

stage 1 - high energy energy photon collides with an inner shell electron, electron is knocked out / ejected
the incoming photon used all of its energy to knock out electron so is absorbed
stage 2 - electron in outer shell drops in to replace missing electron, results in energy loss in form of heat or light

probability of this interaction is atomic number^3
eg bone has higher atomic number so more absorption so look white

Question 3

Absorption and scatter - Compton effect

Answer 3

incoming photon collides with and ejects outer shell electron, some energy absorbed from the photon but not all so photon is deflected in another direction (scattered photon)

free electron replaces lost electron

Question 4

what happens to atoms in tissues with photoelectric and Compton effect?

Answer 4

ionisation - unstable atom becomes positive ion because electron is knocked out

Question 5

Direct Damage

Answer 5

DNA or RNA takes direct hit from X-ray photon which ionises and breaks the bonds between nucleic acids - POINT MUTATION

Radiation induced malignancy - if somatic cells affected
congenital abnormality - if genetic cells are affected

Question 6

Indirect Damage

Answer 6

x ray photon ionises water molecule producing ions and free radicals that combine to form toxic substances which damage DNA
H and OH are free radicals that combine to form toxic substances
eg hydrogen peroxide

Question 7

Final effects of damaging mechanisms are classified as:

Answer 7

somatic deterministic effects
somatic stochastic effects - most likely in dentistry
genetic stochastic effects

Question 8

somatic stochastic effects

Answer 8

somatic - body of person irradiated
stochastic - chance
can be cancer inducing
no known threshold dose
can develop with any amount of radiation
size of exposure does not affect severity of damage, only probability