Week 3 - Radiation Carcinogensis, Protection and Regulations

Explain latent period and the latent period of leukemia compared to solid cancers.

• The time between irritation and appearance of disease.

• Latent period of leukemia is much shorter, 5-15 years, compared to solid cancers that could be up to 60 years

Name and explain the 3 types of risk models

• Absolute - radiation increases cancer rates as a fixed number on top of natural rates

• Relative - radiation increases the natural rate of cancer

• Time-dependent Relative - radiation increases the natural rate of cancer depending on age and time of exposure

Explain the difference between absolute and relative risks

• Absolute risks are the chance of an individual developing a specific disease over a specific time period.

• Relative risks are the comparison between 2 different groups when evaluating their risks of developing cancer

Explain how underground miners developed lung cancer due to radiation exposure.

Underground uranium miners were exposed to Radon (Rn-222) which is a decayed form or uranium, that un

Explain the standardised mortality ratio and give examples

Ratio that compares the mortality of 2 different populations:

• SMR of 1 = same rate for population of interest and standard

• SMR > 1 = greater rate for population of interest

• SMR < 1 = lower rate for population of interest

Explain why pregnant practitioners must reduce their radiation dose to 1mSv per year.

Radiation exposure of 10mSv/mGy can increase the risk of childhood cancer by 40%. Reducing exposure in the first 10 days is critical as there are only few cells developing as well as the last trimester in which organs are forming.

Explain how increasing time increases dose

Dose (Sv) = dose rate (Sv/h) x time (h)

Give the formula and units of dose rate

D = ME/6r² (MicroSv/h)

Where,

• M = activity of source (MBq)

• E = gamma ray energy per disintegration (MeV)

• r = distance from the source (m)

Name and provide example of the 2 types of shielding

• Structural shielding - inbuilt into the department, eg. Lead-lined walls, lead glass etc.

• Personal shielding - personal protective equipment, eg. Lead glasses, aprons etc.

Name and explain the 2 types of structural shielding

• Primary - prevents radiation directly from the beam

• Secondary - prevents deflected/scattered radiation

Name and explain the radiation protection principles.

• Justification - benefits outweigh the risks

• Limitation - dose rates are limited

• Optimisation - dose rates are kept ALARA while ensuring procedures and images are completed effectively

Name and explain the 2 types of radiation licenses

• Management license - given to a facility, allowing for the possession, trade and transport of radiation sources as well as research

• Use license - given to practitioners for use and operation of radiation equipment

List the 6 management license mandatory requirements

• Radiation monitoring and dose assessment

• Storage of radioactive materials

• Labelling and warning signs

• Radiation shielding

• Training

• Emergencies, accidents and incidents