Topic 4: Radiation exposure Flashcards
what are the 3 categories of radiation exposure
- occupational exposure (voluntary)
- medical exposure
- public exposure (imposed)
what is the effective dose limit for occupational exposure
20mSv/yr for radiation workers
what is the effective dose limit for public exposure
1mSv/yr
what is the dose limit for medical exposure
dose limits do not apply to medical exposures
- diagnostic reference levels recommended
what are departments expected to do in the case of medical exposure
survey their own doses, and investigations should be undertaken in XR if doses exceed their levels
what type of radiation contributes to the public most
diagnostic>therapeutic
what are deterministic effects
do not occur below a threshold dose
- severity increases above threshold dose
what is stochastic effects
- no threshold dose
- risk of damage increases as dose increases
- at low doses biological effects not predictable
- BUT always some risk
inherited radiation damage
- does not introduce new, unique mutations
- may increase the incidence of the same mutations that occur spontaneously
the aims of radiation protection
- prevent deterministic effects by keeping doses below threshold
- reduce the risk of stochastic effects to levels considered acceptable
what is absorbed dose
biological effects in any tissue are proportional to amount of energy absorbed per unit mass of tissue
what is equivalent dose (Ht)
different relations have different biological effectiveness for same amount of energy absorbed
what is effective dose
- different organs of body are assigned tissue weighting factors (WT)
- to reflect the different sensitivity of each organ to radiation damage
what is DRL
diagnostic reference levels
- established as a benchmark to ensure doses are kept ALARP while achieving adequate imaging quality
how often are DRLs reviewed
reviewed at 5-year intervals
NPDD
National Patient Dose Database
What are the purpose of national DRLs
DRLs are not dose limits but serve as reference points
- they help identify practices with unusually high or low radiation doses prompting review and optimisation
who are responsible for setting local DRLs
employers responsible
how often are DRLs reviewed
annually
for patient dose surveys, who is the frequency determined by
determined by RPS / manager in consultation with RPA (not less than 3 yearly)
how many patients used for patient dose surveys
at least 10, ideally 20
what happens if patient dose survey larger than DRL
RPS investigates and initiates corrective action
what does IRCP stand for
International commission on radiological protection
who are the IRCP
non-government body expert advisors (200 volunteer scientists)
- make recommendations, either broad or detailed, based on research
is the IRCP mandatory
no, but they are influential
what is the UK legislation
- ionising radiations regulations 2017
- ionising radiations (medical exposures) regulations 2017
the 3 principles of radiation protection
- justification
- optimisation - ALARP
- dose limitation - to staff and general public
where does IRR cover
- hospitals
- dental surgeries
- power stations
- industrial radiography
- research
the duties of the employer according to IRR
- provide safe working environment for staff and public
- themselves, others, patients
RPA
radiation protection advisor
what is the RPA available for
available for advice or assistance of radiation protection issues
- plans for new installations and acceptance into service of new modified radiation sources
- classification of workers/ outside workers
- PPE
- workplace and individual monitoring programmes
- QA
- arrangements for prevention of accidents and incidents
- training and retraining programmes for exposure workers
when must RPA be consulted
- radiation risk assessment
- designation/ implementation of controlled and supervised areas
- investigation and analysis of accidents and incidents
- contingency plans
- dose assessment
- prior examination of new plans
- regular calibration of equipment provided for monitoring levels of ionising radiation
- testing engineering controls
3 restrictions of exposure
- engineering controls and warning devices
- systems of work
- personnel protective equipment
prior risk assessment outcomes
- actions to ensure doses ALARP
- designation of areas
- local rules
- PPE
- dose constraints
- monitoring
- training
IRR 2017 information, instruction and training
- all employees must have received appropriate training for use of equipment
essential contents to the local rules
- dose investigation level
- summary of contingency arrangements
- name of RPS
- identification and description of area covered and its designation
- summary of working instructions
RPS
radiation protection supervisors
RPS role
role is to ensure that on a day to day basis radiation protection are fulfilled
- must be senior and have good knowledge of subject
- link with RPA and management
IRR designation of classified persons
- designated as a classified worker if you receive in excess 6mSV per year
- an employee will not be classified unless they are 18. over - undergone health assessment
when did IRMER 2017 come into force
- came into force 6 Feb 2018
purpose of IRMER
- to protect the patient
- european standard with each country must adhere to
- covers duties of employers and employees in ensuring XR equipment, sheilding and standard operating procedures
who is the employer
- any natural or legal person in the course of trade, business or other undertaking, carries out - engages others to carry out medical exposures at given radiological installation
duties of the employer
- written procedures for medical exposures
- written protocols for every type of standard radiological practice for each equipment
- referral criteria for medical exposure
- QA programmes
- clinical audit
- staff training
- review why reference dose levels are exceeded and take action
what are some of the written procedures that must occur before examinations?
- positive ID procedure
- procedure for enquiries of females of childbearing age
- procedures for giving information and written instructions
what is required from the medical physics expert
- certificate of competence
- underpinning knowledge
- demonstration of practical experience in compliance with IRMER, equipment management and optimisation
who must comply with the employers written procedures
practitioner AND operator
no person shall carry out a medical exposure unless…
it has been justified by practitioner and authorised by practitioner/ operator
