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
What does IR(ME)R2000 outline?
4 levels of responsibility?
- Ionising Radiation (Medical Exposure) Regulations 2000
- Outlines the safety issues and protocols with regard to irradiation of patients, comforters and carers and members of the public.
- Four levels of Responsibility
–Employer
–Referrer
–Practitioner
–Operator
Explain each of the 4 levels of responsibility in IR(ME)R?
- Employer: responsible for maintained equipment, essential protocols, training and record keeping
- Referrer: requests examinations, provides clinical info for justification
- Practitioner: justifies and optimises examinations
- Operator: responsible for carrying out procedure safely; follows ALARP; records doses and reports any incidents
List the responsibilities of staff working under IR(ME)R 2000?
•Responsibilities of staff working under IR(ME)R 2000:
- –Operating procedures
- –Written protocols
- –Clinical audit
- –Incident Reporting
- –Training
- –Justification
- –Optimisation
- –Limitation
Explain patient pregnancy?
- Diagnostic doses to the foetus are extremely unlikely to cause deterministic effects
- No diagnostic doses warrant termination of a pregnancy
- Natural incidence of childhood cancer is 1 in 500
- Doses to the foetus less than 1mGy add a risk of about 1 in 10,000
- Higher dose procedures may double childhood cancer risk
- Justification and ALARP critical
- Check your local policy, including documentation and patient consent
What is the 28 day rule?
- Applied to all procedures involving ionising radiation that would affect the pelvic region
- The woman is asked whether or not she might be pregnant
- If she feels she is unlikely to be pregnant she is asked for the date of the first day of her last period
- If she is within 28 days of that date the examination can proceed provided that the procedure is justified
Why the 28 days?
- For lower dose procedures the evidence suggests that the ‘subsequent risks in the remainder of the first 4-week period would be likely to be so small that no special limitation on exposure is required’ (Sharp, Shrimpton, Bury, 1998)
- The screening process ensures that the woman is unlikely to be pregnant, but if she were, then the risks have been minimised
•
What is the 10 day rule?
- Applied to higher dose examinations such as barium enemas and CT of the abdo/pelvis
- In women of child-bearing age such examinations must be undertaken within 10 days of the onset of their last period
If the woman is outside the 10 day period some Radiology Departments will undertake a pregnancy test which, if negative, means that the procedure can go ahead outside of the 10 day period
Why 10 days?
•It is thought that, due to the ionising radiation dose involved, these particular types of procedure ‘may carry a small risk of cancer induction for the unborn fetus’ (Sharp, Shrimpton, Bury, 1998)
During the first 10 days of the menstrual cycle it is unlikely that conception will have occurred
What is quality assurance?
Who does it?
- Often done by service engineers
- Radiographers can help check collimators, central ray and Bucky alignment
- Fluoroscopy: contrast and resolution tools
- Report and record all errors in log book
- CR cassette cleaning, check for dust/scratches, double erasures
- Clean monitors and check consistent viewing settings
- Reject Analysis
What is reject analysis?
Common reasons for repeats?
- Common reasons for repeats (exposure, positioning, centring, collimation, patient motion)
- Part of Reflective practice
- Record room, exam, exposure factors and why rejected
- Can identify areas needing improving
- May identify equipment faults/differences
- Not a test! Use them educationally
- Usually 3-10%, aim to improve but not at the expense of quality standards
Explain comforters and carers in an examination?
- Departmental guidelines to be used whenever a patient needs to have another person alongside them during a radiological examination.
- Requires informed consent as there is no medical justification for the dose received.
- Check for pregnancy
- Radiation protection techniques
- Documentation of carer involvement
What are the principles of staff does reduction?
- Time: Shorten exposure, shorten time in vicinity of radiation (i.e. does everyone in the room need to be there?)
- Distance: Inverse Square law, direction of primary beam?
- Shielding: Lead screens, lead aprons etc.
- Personal Dose Monitoring
Many factors influence the effects of ionising radiation, list some?
- Age- younger radiosensitive
- Area received- sensitivity of area
- How dose received- long in one, separate
- Area size
