Radiation protection & legislation Flashcards
what 3 bodies need protecting against radiation
1) staff and students
2) patients
3) members of the public
what are the three broad categories of radiation exposure
1) occupational
2) medical (patients)
3) public
the additional risk of fatal cancer imposed on the ‘average’ individual by exposure to radiation at low doses and low dose rates can be estimated by using a risk coefficient of
0.05 per Sievert
often expressed as 5 x 10^-2 (or 5%) per Sievert
the risk is then calculated by:
risk= effective dose in Sieverts x (5 x 10^-2)
what two words describe radon as a gas
colourless and odourless
where does radon come from
the radioavtive decay of the tiny amounts of natural uranium and thorium in rocks, soils and many building materials
what is the single largest contributor to background radiation dose
radon
what happens when daughter products of radon attach to dust particles
when breathed in, they irradiate the lung with alpha particles an increase the risk of lung cancer
what % of all lung cancers in the UK are caused by radon
3-5%
what is the UK annual dose from radon
1.3 mSv
what is the action level concentration of radon in home
22 Bq/m^3
how does radon get into the air
diffuses from the ground and building structures to give a measurable, but not problematic, concentration in the atmosphere in open air
where do higher, problematic concentrations of radon occur and why
within buildings, partly as a result of diffusion from the structural materials but also because radon from the ground can enter the building
concentration varies with
geographical location depending upon the uranium content of the underlying geology
in radiography what three sources are we protecting from
1) primary x or gamma radiation
2) secondary (scattered radiation)
3) radioactive sources (sealed and unsealed)
facts about scatter or ‘secondary radiation’
- is x or gamma radiation
- of lower intensity than the primary x-ray beam which caused it
- of lower energy than the x or gamma ray photon which caused it
- contributes an additional dose of radiation to the patient
the amount of scatter produced increases as
the volume of the part being irradiated increases
how can you reduce scatter
- collimation of the primary beam
- use a higher (keV) photon energy of the primary beam
in what direction does scattered travel
ALL directions, tends to go in a more forward direction and be more penetrating as the energy of the primary beam increases
how does scatter effect image quality
has a detrimental effect as it reduces contrast on the image. Therefore it requires the use of a ‘grid’, which itself requires an increase in exposure to the patient
the risk of radiation is greater in children than for adults because (2 things)
- for delayed effects e.g. cancer induction there is longer ‘alive’ period for it to show
- children have higher likelihood of having children in future, so genetic effects higher
3 main aims of radiation protection
1) prevent deterministic effects
2) limit stochastic effects to a minimum
3) ensure radiation exposure is justified
(ABC) key principles in achieving the aims of radiation protection
A- justification
there must be no exposure unless it provides NET BENEFIT
B- optimisation
Keep all justifiable exposures ALARA/P
(as low as reasonably achievable/practicable)
C- dose limitation
legal limits on the radiation dose for occupational/ public exposure
DOES NOT APPLY TO PATIENTS
3 framework for protection
1) ICRP recommendations
2) European Legislation
3) UK Legislation
- radiation protection
- environment
- transport
ICRP recommendations have published for 50 years on
- philosophy of radiation protection- ABC
- ose limits
- dosimetric quantities and data
European legislation
basic safety standard laid down in Basic Safety Standards Directive (BSS 2013/59)
uk legislation have two main regulations:
- IRR (ionising radiations regulations) 1999
- IR(ME)R (ionising Radiation Medical Exposure Regulations) 2000
who is IRR 99 protecting
employees and members of the public
who is IR(ME)R 2000 protecting
patients
who polices IRR 99
The health & Safety Executive (HSE). failure to comply is an offence
what are the requirements: (8 things)
- arrangement for the management of radiation protection of employees (appointment of RPA and RPS)
- suitable training of staff
- risk assessments
- dose limits for workers
- designation of controlled and supervised areas
- local rules
- maintenance of personal protective equipment and of engineering controls
- availability of an approved dosimetry service
what is the main duty of the radiation protection adviser (RPA) and who is it usually
(typically a physicist) the role of the RPA is to advise an employer on compliance with IRR99 and related legislation
RPA is responsible for: (10 things)
1) approval of local rules
2) carrying out risk assessments
3) designation of controlled and supervised areas
4) the conduct of investigations into incidents
5) contingency planning
6) patient and staff dose assessment and recording
7) ensuring a system of QA is in place
8) prior examination of plans for installation and acceptance into service of new or modified sources of radiation
9) periodic examination and testing of engineering controls, safety features and system of work
10) calibration and use of monitoring equipment
who is usually the radiation protection supervisor (RPS)
typically a suitably experienced radiographer
their two main roles are:
1) maintain proper standard of radiation protection within the controlled and supervised areas for which he/she is responsible as set out in the IRR 99, the associated notes for guidance an the local rules
2) ensure that all staff are familiar with, have signed and follow the Departmental Local Rules
the RPS must notify the Radiation Protection Adviser if: (3 ways)
1) any personal dosemeter record shows a reading above the investigation level
2) there is any change in practice procedures which might result in significant increase in doses received by members of staff
3) there is any change in equipment e.g. new X-ray apparatus
4) maintenance work is performed on x-ray equipment which could affect its radiation output
5) maintenance work is performed on the structure of the x-ray room which could affect its radiation shielding properties
what is the limited dose introduced by the IRR 99 for employees aged 18 years or over
20 millisieverts in a calendar year
what is the limited dose introduced by the IRR 99 for trainees
6 millisieverts in a calendar year
what is the limited dose introduced by the IRR 99 for any other person, including members of the public an employees under 18 who cannot be classed as trainees
1 millisieverts in a calendar
workplaces are subject to classified as 2 things:
1) controlled area
2) supervised area
what is a controlled area
an area where the time averaged dose exceeds 7.5uSv per hour
what is a supervised area
where no special procedures are normally needed but exposure conditions are kept under review
examples of controlled areas
- all x-ray and treatment rooms are controlled areas only when the radiation equipment is switched on
- operating theatres
- parts of wards, when mobiles in use
what are the local rules
under IRR99, each treatment room must have them
what do the local rules include:
- clear description of the area to which they apply
- names of appointed persons (RPA/RPS) and how to contact them
- their duties and responsibilities
- classification of work areas
- systems of work
- operational procedure incl personal monitoring/personal protective equipment
- contingency plans
how are we personally monitored
- dose badge to make sure dose is low.
- normally TLD or film badge
- worn as instructed by local rules (waist level etc)
- NOT to be left in controlled areas
- special monitors for hands, eyes etc
what must you do if you are pregnant
declare it to your employer in writing
foetal dose must be less than
1 mSv
what is the feotus considered as
a member of the public
who polices IR(ME)R
The Care Quality Commission (CQC)
what is the purpose of IR(ME)R
- protect patients from unintended, excessive, incorrect or inappropriate medical exposures
- ensure the benefits outweigh the risk in every case
- make patients receive no more than the required exposure for the desired benefit, within technological limits
where does the responsibility lie for compliance with IR(ME)R
the employer
5 key personnel’s defined under IRMER are
- employer
- medical physics expert
- referrer
- operator
- practitioner
employer definition
normally the NHS trust
definition of medical physics expert
a suitably trained person who is competent to advise on matters such as patient dosimetry, evaluation of unintended exposures and proposed new practices
definition of referrer
the person requesting the radiation exposure
definition of practitioner
the person who reviews the request from the referrer and agrees by signature that the request is justified based upon clinical information provided. can be the radiographer/radiologist
definition of operator
anyone who carries out the practical aspects of any exposure. can be the radiographer/radiologist
what can be done to minimise the risks to staff and students
- education and awareness
- follow local rules
- use shielding
- maintain optimum distance- use inverse square law
- keep exposure time to a minimum
- avoid repeats
- personal dose monitoring
how do we minimise risks to patients
- only use radiation when justified
- education of staff
- avoid repeats
- use correct techniques
- shield radiosensitive areas
- filter the primary beam
- use a ‘sensitive’ imaging system
- regular and effective quality control
how to minimise risks to members of the public
- clearly designed and obvious radiation warning signs outside of x-ray/treatment rooms
- close doors to all x-ray.treatment rooms
- shielding of walls adjacent to waiting areas
