RS Flashcards
Deterministic effects
High dose (> 100 mSv)
Tissue damage
DIfferent thresholds for different organs
Stochastic effects
low and long-term radiation exposure
no threshold
severity of effects is independent of dose
What is the LNT model?
Probability of stochastic effect increases proportional with the dose.
No threshold for effects to appear.
At high doses there is a clear linear relationship between risk and dose.
What are some limitations of the LNT model?
- need a large sample size to get a useful degree of precision
- at very low doses it is hard to correlate any irradiation with certain bio-effects as the baseline cancer rate is high (40%)
- doesn’t take into account the adaptive response of the body.
Threshold model
there is a threshold below which there is no risk
different for each person
can lead to reduction of exposure limits
Hormesis Model
low doses may have a positive effect
cellular repair is simulated, enhancing the body’s response
Supralinear Model
risk from low doses is higher than expected
irradiatied cells may damage neighbouring cells
takes into account sensitive sub-groups
Bell-shaped Model
cells are killed, therefore, risk decreases
ignores repair-repopulation
Plateau Model
increase risk as more cells are mutated
takes into account repopulation
risk reaches a plateau at high doses
Full Mechanistic Model
cells are killed but not fully repopulated
every tissue has a different ability to repopulate
takes into account fractionation
man-Sievert
the dose accumulated by a group of people
Cost-benefit analysis
net benefit = gross benefit
-production cost
-cost of protection
-cost of detriment (man-Sv)
What are the five steps of a risk assessment?
- Identify the hazard
- Identify who is harmed
- Evaluate risks
- Record findings
- Review and revise
What should be included in a risk assessment?
- description of work
- sources of radiation
- dose rate estimates
- contamination
- control measures
- accidents
- actions
Radiation Accident
an accident where immediate action would be required to prevent or reduce exposure
requires a contingency plan
What is a Practice?
a human activity that can increase the exposure of individuals to radiation from an ionising radiation source
What is an Intervention?
activities that seek to reduce the existing radiation exposure, or the likelihood of incurring exposure
How is a Practice justified?
benefits should outweigh the risks of ionising radiation
take into account social, political, and radiological aspects
How are Interventions justified?
should do more good than harm, having regard to health, social and economic factors
When do dose limits not apply?
medical exposures
urgent/emergecy interventions
Planned Exposure
activities considered as Practicies or potential exposure situations from forseeable accidents
dose limitation, optimisation through dose constraints
Emergency Exposure
a non-routine situation that necesitates prompt action to mitigate a hazard or adverse consequence for human health and safety
optimisation through dose reference levels
Existing Exposure
situation that already exists when a decision on control has to be taken (eg NORM)
optimisation through dose reference levels
Healthcare occupational dose constraint
0.3 mSv/yr
What are dose constarints for occupatinal exposures used for?
limit the range of options considered in optimisation
What are dose constarints for public exposures used for?
an upper bound of any annual dose to be received for planned operation of a controlled source
Representative Person
an individual receiving a dose that is representative of the more highly exposed individuals in a population
Critical Group
those most highly exposed by the source
NORM
Naturally Occuring Radioactive Material
a RAM containing no significant amounts of radionuclides other than naturally occuring radionuclides
Radon action level
200 Bq/m^3
Work in a radon atmosphere
> 300 Bq/m^3
HSE should be notified
How is randon conc. measured?
an etched track type detector is placed in situ for 3 months and the results are converted to an annual average
Control measures for radon
increase ventilation
sealing gaps and cracks
fans
rubber membranes
Accidental Patient Exposure
an individual has received an exposure when no exposure was expected
Unintended Exposure
although an exposure was intended, the exposure the individual received was significantly greater or different to what was intended
Clinically Significant Accidental or Unintended Exposure
an exposure which leads to a risk of 1 in 1,000 or one which has caused harm to the individual (e.g psychological harm)
What is a research exposure?
an exposure which is required as an integral part of, and for, the puposes for research:
* confirm eligibility
* assess disease baseline
* image guided procedures
What do the Health Research Authority do?
- ensure that research is ethically reviewed and approved
- provide recommendations on the processing of patient data where it is not practical to obtain consent
(HRA managed radiation assurance)
Which docs are reviewed during radiation assurance?
- trial protocol
- research exposure form
- participant info sheet
What does an MPE research review consist of?
- dose and radiation risk assessment
- advice on wording for PIS
- use of national DRLs
What does an CRE research review consist of?
advice on the suitability and justification for additional exposures
Cancer risk coefficient
5% per Sv
What is the aim of the Research Ethics Committee?
safeguard the rights, safety, dignity and well-being of participants
What does an MPE do?
give advice on matters relating to radiation physics applied to medical exposures:
* optimisation of patient doses
* acceptance testing of new equipment
* radiation protection training to practitioners
Who is involved in the RP management framework?
- employer
- RPA
- MPE
- RPS
- managers with RP resonsibilities
What is the purpose of a radiation protection comittee?
- write and approve RS docs
- review personal monitoring and incodents
- take action to ensure compliance
- discuss training issues
What is the purpose of a medical exposure comittee?
- write and approve IRMER docs
- review patient does and DRLs
- optimise doses
What is the purpose of an audit?
- check and demonstrate compliance with regs
- identify issues and encourage improvement
Types of audit
- CQC (clinical audit)
- HSE (IRR audit)
What are the classification doses?
whole body dose: 6 mSv
eye dose: 15 mSv
skin/extremity dose: 150 mSv
Who is a classified worker?
an individual who works with a source of ionising radiation capable of exposing a person to a dose rate such that a dose limit would be exceeded within a few minutes
Who is an Appointed Doctor?
a registered medical practitioner who has been appointed by the HSE and they must certify that a classified worker is fit to work with ionising radiation
What is an outside worker?
a person who enters a controlled area of another employer to provide a service
What arrangements should be made for outside workers?
- AxREM form to handover the controlled area
- OW employer should provide passbook and dosimetry from ADS
- CA employer must arrange for estimated dose to be entered into passbook
- Employers should exchange info regarding entry arrangements and training requirements
When is co-operation of employers required?
when work with ionising radiation undertaken by one employer is likely to give rise to the exposure to radiation of the employee of another employer
What is the HSE graded approach to Practices?
- Notification
- Registration
- Consent
Notification requirements
work with < 1,000 kg of artificial or naturally occurring radionuclides
no evidence required
Registration requirements
- radiation generators, x-ray devices
- > = 1,000 kg of RAM that is above low end conc levels
- < 1,000 kg of RAM that is above medium conc levels
no evidence required
What do the HSE require confirmation of before Registration?
- local rules
- appointment of RPS
- number of different types of equipment
- risk assessment
- controlled and supervised areas
What are some Practices which require Consent?
- administering radionuclides
- addition of radioactive substances into products
- operation of an accelerator (LINAC)
- long-term storage of RAW
requires full radiation assessment and inspection
What does a HSE radiation safety assessment consider?
- number of employees
- details of equipment/radionuclides
- dose rates
- engineering controls
- results of critical exam
- copies of local rules and risk assessment
What is considered during an investigation of a staff incident?
- work routine of individual and colleagues
- radiation monitors
- adherence to local rules
- any known incidents
- training
What would the HSE like to see during an inspection?
- radiation safety policy
- risk assessments
- local rules
- critical exams
- environmental monitoring results
- training records
What would the CQC like to see during an inspection?
- radiation safety policy
- IRMER procedures
- clinical audits
- QA records
- training records
What do the ICRP do?
International Comission on Radiological Protection
* provide a framework for national regs
* dose limits
* ALARA (supports LNT model)
What do UNSCEAR do?
United Nations Scientific Committee on Effects of Atomic Radiation
* provide scientific basis for radiation protection
* assessment and reporting of levels and effects of ionising radiation
What do the ICRU do?
International Comission on Radiological Units
* develop recommendations on quantities and units for radiation and radioactivity, terminology, procedures for measurements
What do the IAEA do?
International Atomic Energy Agency
* provides practical support and guidance regarding nuclear safety, security, science
* publishes BSS based on ICRP docs
What are the annual dose limits for radiation workers?
Whole body: 20 mSv
Eye: 20 mSv
Skin/Extremities: 500 mSv
What is the annual public dose limit?
1 mSv
