Radiation Protection Flashcards
What is the goal of ‘radiation protection’?
•The goal of radiation protection is to limit human exposure to Ionising Radiation thereby reducing the likelihood of somatic and genetic effects.
What percentage of human radiation dose comes from natural causes?
84%
What is an ionisation?
What causes it in the body?
- Change in molecular structure and charge due to gain/loss of electrons
- In the body this can lead to cell death or genetic mutations
- Using diagnostic radiography, ionisation occurs due to
–Photoelectric Absorption, and,
–Compton Scatter
What is the somatic effect of radiation?
•If individual is effected – Somatic effect
What is the genetic effect of radiation?
Name some genetic effects
- If effects damage reproductive cells, it will effect future generations – Genetic effect
- Genetic effects include:
–Malformation or damage/death to the Foetus
–Genetic aberrations/mutations in next generation
–Cancer in next generation
What are stochastic effects?
•Stochastic (random) effects
–Cannot predict with certainty
–Risk rises with dose
–Eg Cancer induction, genetic effects
What are deterministic effects?
•Deterministic effects
–Certainty effects will happen
–Threshold dose
–E.g. Cataracts after 5Gy – 100 % risk
–Skin erythema, hair loss, skin burns (2-5Gy)
What is the ‘absorbed dose’?
•Absorbed Dose: Gray (Gy) defined as one joule of energy absorbed by one kilogram of matter
What is ‘equivalent dose’?
•Equivalent Dose: Sievert (Sv). Also allows for type of radiation and its effect on tissue with a quality (Q) weighting factor. Equivalent Dose therefore equals Absorbed Dose x Q (but Q equals 1 for X and gamma rays!)
What is the effective dose?
•Effective dose: Sievert (Sv) also allows for differing radio sensitivities of different organs/tissue, so will be the sum of all the equivalent doses in each tissue x a tissue weighting factor based on radio sensitivity for each organ.
Other dose indicators
What is the DAP?
EI?
ESD?
DRL?
- Dose Area Product (DAP): Is the absorbed dose leaving the x-ray tube multiplied by the area irradiated (in mGy.cm2)
- Exposure Index (EI): Indicates amount of radiation incident on IR
- Entrance Skin Dose (ESD): Absorbed Dose at the entry point of the patient
- Dose Reference Level (DRL): 75th percentile of absorbed doses for a typical patient for a specific procedure

What is current radiation risk based on?
Fatal cancer risk?
Hereditary effects?
- Current risk estimates based largely on Japanese bomb survivors or epidemiological studies
- Risk of:
–Fatal cancer ~ 1 in 20,000 per mSv
–Hereditary effects ~ 1 in 50,000 per mSv
Patient radiation dose
Fill in the table


What is the annual natural radiation dose?
Annual average medical exposure?
Radiation workers limit?
General public radiation limit?
Pregnancy radiation limit?
- Annual Natural Radiation Dose: 2.2mSv per year
- Annual average medical exposure: 0.4mSv
- Radiation Workers Radiation Limit : 20 mSv per year
- General Public Radiation Limit: 1mSv per year
- Pregnancy Radiation Limit : 1mSv per year to foetus
What are the radiation safety legislations?
- IRR99 - The Ionising Radiations Regulations 1999
- IR(ME)R 2000 – Ionising Radiation (Medical Exposure) Regulations 2000
Outline The IRR99?
•The Ionising Radiations Regulations 1999
–Part of “Management of Health and Safety at Work Regulations”.
–Concerned primarily with staff safety and Radiation Protection framework
–Replaced IRR85
What does the IRR99 outline?
•Outlines aspects of safety that are relevant to staff using radiation:
- –Role and requirements for RPA (Radiation Protection Advisors) and RPS (Radiation Protection Supervisors)
- –Controlled areas
- –Local Rules
- –Risk assessments
- –Personal monitoring and dose limits
- –Pregnant and breastfeeding employees
- –ALARP investigation level
What is an RPS?
•Radiation Protection Supervisors (RPS): Nominated staff member responsible for ensuring regulations are followed at department level
What is an RPA?
•Radiation Protection Advisors (RPA): Specialists who advise employers on the safe use of radiation under IRR99
What is a controlled area?
- An area deemed as requiring special radiation safety conditions after risk assessment. Defined as an area where workers are at risk of receiving three tenths of their annual occupational limit.
- Should be well signed and described in local rules, and governed by RPS
- Personal dosimetry mandatory
- Still applies to Fluoroscopic and Mobile examinations
What are local rules?
- Local Rules are compulsory written rules and procedures governing the safe use of ionising radiation in the work place.
- They are designed to enable work to be carried out in such a way as to minimise the risk to the operator, colleagues, and any other person who may be affected by the use of radiation.
- Staff should not work in controlled areas without first reading and understanding the Local Rules.
What do the local rules give detail of?
The local rules give details of:
- Names and contact details of RPA and RPS
- Details of controlled areas
- All working protocols and procedures for the department
Contingency plans
What is ALARP?
- As Low As Reasonably Practicable
- All reasonable steps must be taken to ensure dose to staff, patients and the public are kept as low as possible
Explain how pregnancy effects students under IRR99?
- Under IRR99, there is an onus on female students to notify the University as soon as possible in writing, in the event of pregnancy or breast-feeding so that risk assessments can be made.
- If local rules are followed however, it is extremely unlikely that a pregnant woman/foetus or breast feeding woman/baby would be put at risk