Radiation Safety

Question 1

What are the main types of biological effects of radiation?

Answer 1

Deterministic effects: those we know will occur

Non deterministic/stochastic effects: those which may occur

Question 2

What are deterministic effects?

What are some biological deterministic effects?

Answer 2

Deterministic effects:

• definitely occur with specific doses
• threshold dose: below threshold the effect does not occur, but above the threshold dose effects will always occur
• affects the patient directly being exposed –> somatic effects
• can be used positively for cancer patients with radiotherapy

Acute biological effects:

• radiation sickness 2-10Sv whole body irradiation (symptoms within a few hours)
• death > 10Sv whole body radiation

Chronic deterministic effects:

• hair loss, cataracts, sterility, obliterative endarteritis

Question 3

What are non deterministic effects?

Answer 3

Non deterministic effects: occur at random

• no threshold dose (like playing a lottery)
• damage affects pt and future children
• somatic and genetic effects
• amount of damage not dose related
• less chance of damage with low dose
• somatic effects - development of malignancy
• genetic effects - congenital abnormality which may include malignancy - will only occur if reproductive organs exposed to radiation

Question 4

What types of effects are we likely to have in dentistry?

What factors affect dose of radiation?

Answer 4

Non deterministic effects –> problem!

Factors affecting dose of radiation:

• type of radiation
• tissues being irradiated
• age of patient

Question 5

What are dose limitations?

What is the dose limit for patients?

Answer 5

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

No set dose limits for patients but should be As Low As Reasonably Practicable (ALARP)

Question 6

Who is more at risk of developing adverse effects of radiation?

What do we need to consider before taking a radiograph?

Answer 6

Young patients are more at risk of developing adverse effects of radiation as opposed to elderly patients

Must weigh out information desired against radiation dose to patient, to ensure benefits outweigh risks.

Question 7

What are some practical means of dose reduction?

Answer 7

• avoid unnecessary radiographs
• use of selection criteria
• film speed - preferably use F speed
• kV of machine - higher the kV, lower the dose
• rectangular collimation
• collimated DPT views
• regular servicing of machines
• knowledge and understanding

Question 8

What is the controlled area?

What should the control area be?

Answer 8

Controlled area - area around patient and x-ray tube, rest of area a NO GO zone

X-ray machines <70kV - 1.5m in diameter

• but size depends upon local rules
• DDH stand 2m away for all machines or behind appropriate shielding