Radiation protection & legislation Flashcards
what 3 bodies need protecting against radiation
1) staff and students
2) patients
3) members of the public
what are the three broad categories of radiation exposure
1) occupational
2) medical (patients)
3) public
the additional risk of fatal cancer imposed on the ‘average’ individual by exposure to radiation at low doses and low dose rates can be estimated by using a risk coefficient of
0.05 per Sievert
often expressed as 5 x 10^-2 (or 5%) per Sievert
the risk is then calculated by:
risk= effective dose in Sieverts x (5 x 10^-2)
what two words describe radon as a gas
colourless and odourless
where does radon come from
the radioavtive decay of the tiny amounts of natural uranium and thorium in rocks, soils and many building materials
what is the single largest contributor to background radiation dose
radon
what happens when daughter products of radon attach to dust particles
when breathed in, they irradiate the lung with alpha particles an increase the risk of lung cancer
what % of all lung cancers in the UK are caused by radon
3-5%
what is the UK annual dose from radon
1.3 mSv
what is the action level concentration of radon in home
22 Bq/m^3
how does radon get into the air
diffuses from the ground and building structures to give a measurable, but not problematic, concentration in the atmosphere in open air
where do higher, problematic concentrations of radon occur and why
within buildings, partly as a result of diffusion from the structural materials but also because radon from the ground can enter the building
concentration varies with
geographical location depending upon the uranium content of the underlying geology
in radiography what three sources are we protecting from
1) primary x or gamma radiation
2) secondary (scattered radiation)
3) radioactive sources (sealed and unsealed)
facts about scatter or ‘secondary radiation’
- is x or gamma radiation
- of lower intensity than the primary x-ray beam which caused it
- of lower energy than the x or gamma ray photon which caused it
- contributes an additional dose of radiation to the patient
the amount of scatter produced increases as
the volume of the part being irradiated increases
how can you reduce scatter
- collimation of the primary beam
- use a higher (keV) photon energy of the primary beam
in what direction does scattered travel
ALL directions, tends to go in a more forward direction and be more penetrating as the energy of the primary beam increases
how does scatter effect image quality
has a detrimental effect as it reduces contrast on the image. Therefore it requires the use of a ‘grid’, which itself requires an increase in exposure to the patient
the risk of radiation is greater in children than for adults because (2 things)
- for delayed effects e.g. cancer induction there is longer ‘alive’ period for it to show
- children have higher likelihood of having children in future, so genetic effects higher
3 main aims of radiation protection
1) prevent deterministic effects
2) limit stochastic effects to a minimum
3) ensure radiation exposure is justified
(ABC) key principles in achieving the aims of radiation protection
A- justification
there must be no exposure unless it provides NET BENEFIT
B- optimisation
Keep all justifiable exposures ALARA/P
(as low as reasonably achievable/practicable)
C- dose limitation
legal limits on the radiation dose for occupational/ public exposure
DOES NOT APPLY TO PATIENTS
3 framework for protection
1) ICRP recommendations
2) European Legislation
3) UK Legislation
- radiation protection
- environment
- transport