radiation safety

Question 1

what are the biological effects of radiation?

Answer 1

• Those we know WILL occur = deterministic (non stochastic)
• Those which MAY occur = non-deterministic (stochastic)

Question 2

describe deterministic effects

Answer 2

• 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

Question 3

describe deterministic effects (acute and chronic)

Answer 3

(a) AcuteRadiation sickness 2-10 Sv whole bodyirradiationDeath >10 Sv whole body irradiation(b) ChronicHair lossCataractsSterilityObliterative endarteritis

Question 4

describe non-deterministic effects

Answer 4

• 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

Question 5

which type of effects are we likely to have in dentistry?

Answer 5

Non-deterministic and that is the problem

Question 6

factors affecting dose of radiation

Answer 6

1) type of radiation - we are interested only in x-rays
2) tissues being irradiated
3) age of the patient

Question 7

what are the dose limits per annum?

Answer 7

classified worker - 50 mSv (old), 20 mSv (new)
non-classified worker - 15 mSv (old), 6 mSv (new)
general public - 5mSv (old), 1 mSv (new)

Question 8

Dose limitation

Answer 8

• Applies to workers
• NRPB estimated mean dose for dental workers <0.1mSv
• recommended that should never exceed 1mSv (dose limit for public)

Question 9

What does ALARP stand for?

Answer 9

• As
• Low
• As
• Reasonably
• Practicable

Question 10

what are some food that are radioactive - mainly from radioactive potassium?

Answer 10

• brazil nuts
• butter beans
• bananas
• potatoes
• carrots
• red meat
• avocado
• beer
• water
• peanut butter

Question 11

What are some practical means of dose reduction?

Answer 11

• 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

Question 12

intensity & the inverse square law why are they important?

Answer 12

the number of “photons” in a beam at a specific place

Question 13

describe controlled area

Answer 13

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