radiation safety Flashcards
what are the biological effects of radiation?
- Those we know WILL occur = deterministic (non stochastic)
- Those which MAY occur = non-deterministic (stochastic)
describe deterministic effects
- definitely occur with specific doses
- threshold dose
- below threshold the effect does not occur
- all the damage effects the person exposed to the radiation
- Somatic effects
- think about a patient who is being treated for cancer with radiotherapy
describe deterministic effects (acute and chronic)
(a) AcuteRadiation sickness 2-10 Sv whole bodyirradiationDeath >10 Sv whole body irradiation(b) ChronicHair lossCataractsSterilityObliterative endarteritis
describe non-deterministic effects
- occur at random - chance or probability
- “just like playing the lottery”
- no threshold dose
- damage affects patient & also future children
- somatic and genetic effects
- amount of damage not related to dose
- less chance of damage with low dose
- somatic effects - development of malignancy
- genetic effects - congenital abnormality which may include malignancy
which type of effects are we likely to have in dentistry?
Non-deterministic and that is the problem
factors affecting dose of radiation
1) type of radiation - we are interested only in x-rays
2) tissues being irradiated
3) age of the patient
what are the dose limits per annum?
classified worker - 50 mSv (old), 20 mSv (new)
non-classified worker - 15 mSv (old), 6 mSv (new)
general public - 5mSv (old), 1 mSv (new)
Dose limitation
- Applies to workers
- NRPB estimated mean dose for dental workers <0.1mSv
- recommended that should never exceed 1mSv (dose limit for public)
What does ALARP stand for?
- As
- Low
- As
- Reasonably
- Practicable
what are some food that are radioactive - mainly from radioactive potassium?
- brazil nuts
- butter beans
- bananas
- potatoes
- carrots
- red meat
- avocado
- beer
- water
- peanut butter
What are some practical means of dose reduction?
- Avoid unnecessary radiographs
- use of selection criteria
- film speed - preferably use F speed
- digital radiography may help
- kV of machine - higher the kV, lower the dose
- rectangular collimation
- collimated DPT views
- regular servicing of machines
- knowledge & understanding
intensity & the inverse square law why are they important?
the number of “photons” in a beam at a specific place
describe controlled area
Only the patient can be in the controlled area during exposure Size depends on kV of machine 1.5m for under 70kV BUT size depends on Local Rules DDH stand 2m away for all machines Or behind appropriate shielding