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The two main pieces of legislation are:

  • IR(ME)R 2017: deals with exposure to patients for medical and non-medical procedures (also IR(ME)R 2018(NI) and IR(ME)R (amendment) 2018)
  • IRR 17: deals with exposure to employees and the public

For Nuclear Imaging, there is specialised legislation:

  • EPR 16 (previously RSA 93): deals with storage and disposal of radioactive substances. Governs institutions.
  • CDG 2009 (previously RM(RT)R 2001): deals with transport of radioactive substances

The Ionising Radiation (Medical Exposure) Regulations (2017) (IRMER 2017)

Resource: IR(ME)R 2017

Governs all medical and, since 2017, non-medical exposures to patients.

  • Justification (net risk to patient in when considering risk of radiation and risk of not having the investigation)
  • Optimisation (lowest dose that gives an image quality sufficient for diagnosis to be made. This does not mean the best image quality achievable with the equipment)
  • Clinical audit
  • Training
  • Research exposure
  • Medico-legal exposure
  • Significant accidental or unintended exposures (SAUE)
    • Need to minimise the possibilities of incidents occurring
    • Includes cases of operator, procedure or equipment failure


A new requirement is that patients must be informed of the benefits and risks prior to the exposure taking place. Comforters and carers must be exposed knowingly and willingly indicating they, too, must be consented and made fully aware of the potential risks of radiation exposure. Also, licensing of practitioners and employers/facilities for the administration of radioactive substances has now been brought into IRMER.

*** The main mantra of IMER is ALARP ***

As Low As Reasonably Practicable

Diagnostic Reference Levels (DRLs)

Resource: National Diagnostic Reference Levels 19 August 2019 onwards

Gives guideline of doses, not legal limit (there is no limit for patients but doses should be as low as reasonably practicable). These will vary from centre-to-centre, patient-to-patient, and with the complexity of the case (e.g. fluoro/interventional). Doses are audited every three years and the median shouldn’t vary significantly from the DRL. There are also local DRLs in each hospital/Trust which are usually lower than the national DRLs.

For the values please refer to the Appendix.

Roles and responsibilities


  • Health care professional entitled in accordance with employer’s and local procedures to request and refer individuals for medical exposure
  • Required to supply practitioner with sufficient medical information


  • Required to justify all medical exposures and decide if exposure is in patient’s best interest (e.g. person who vets requests)
  • Can be the radiologist or radiographer


  • Carries out and optimises the medical exposure
  • Includes radiographer (pressing the exposure button, identifying patient, processing images, checking pregnancy status, etc) and technician performing annual quality assurance tests
  • May have responsibility for authorising exposures under written guidance from a practitioner e.g. radiographers in walk-in chest x-ray lists can justify AND carry out procedure, i.e. practitioner and operator
  • Responsible for optimisation (ALARP)


  • Implements IRMER and allocates individuals to roles
  • Provide written procedures and protocols
  • Ensure staff are appropriately trained
  • Respond where an incident has occurred

Medical Physics Expert

  • Requires national recognition certificate
  • Involved in:
    • Patient dosimetry
    • Equipment management
    • Optimisation
    • Advice on regulatory compliance


  • Referrer doesn’t need to justify procedure
  • Practioner justifies exposure
  • Operator optimises exposure, ensures ALARP followed, and operates image intensifier in fluoroscopy (may also be practitioner)
  • One person can perform many different IRMER roles. The person pressing the exposure button is an operator, even if they are also the practitioner. In some cases, such as dental exams, one person can be the referrer, practioner and operator.

Written by radiologists, for radiologists with plenty of easy-to-follow diagrams to explain complicated concepts. An excellent resource for radiology physics revision.

Ionising Radiation Regulations 2017 (IRR17)

Resource: IRR17

Made under the Health and Safety at Work Act 1974 and designed to minimise radiation exposure to employees and members of the public. They are enforced by the Health and Safety Executive (HSE) and outlined in the Approved Code of Practice and guidance.

  • Designed to ensure exposure to workers and members of the public follows ALARP
  • Final responsibility for radiation safety lies first and foremost with the employer. In an NHS Trust this is the CEO.

Roles and Responsibilities

Radiation protection adviser

  • Usually an expert physicist and should be trained in the use of radiation and have thorough knowledge of the associated hazards and their control
  • Must have a certificate of competence issued by a body recognised by the HSE
  • Advises on:
    • Identification and designation of controlled and supervised areas
    • Calibration of monitoring equipment
    • Risk assessments
    • Drawing up of local rules and contingency plans
    • Quality assurance programmes

Radiation protection supervisor

  • Appointed by employer
  • Ensures local rules are being complied with
  • Must know what to do in an emergency
  • Must always be present on site
  • There can be more than one radiation protection supervisor for each controlled area


  • Not knowingly expose themselves or others to ionising radiation to a degree that is greater than necessary
  • Make full and proper use of Personal Protective Equipment and report any defects in it
  • Inform the employer about suspected incidents

Radiation risk assessment

This is mandatory before starting a new activity or changing an activity involving ionising radiation

  • Identify hazards
  • Decide who may be harmed and how
  • Evaluate the risks and decide on precautions
  • Record your findings and implement them
  • Review your assessment and update if necessary
  • The risk assessment informs the local rules

Dose limits per calender year

To limit stochastic effects the effective dose limits are:

Employees and trainees 18 years old or more

20 mSv or

100 mSv in any period of five consecutive calendar years subject to maximum equivalent dose of 50 mSv in any single calendar year

Trainees < 18 years old

6 mSv

(i.e. < 3/10 of adult dose)

Anyone < 16 years old or any person other than employee or trainee1 mSv
Dose limit to abdomen of person of reproductive capacity13 mSv in any consecutive 3 months
Any person (not carer or comforter) that may be exposed to ionising radiation resulting from medical exposure of another person5 mSv in any period of 5 consecutive calendar years
Dose to fetus of pregnant employees1 mSv for remainder of pregnancy

To prevent deterministic effects the equivalent dose limits in a calendar year are:

AreaEmployees and trainees 18 years old or moreTrainees under 18 years oldAny person (not carer or comforter) who may be exposed resulting from medical exposure of another person
Lens of the eye20 mSv in a calendar year averaged over 5 years with no single year exceeding 50 mSv15 mSv15 mSv
 Extremities 500 mSv 150 mSv 50 mSv
 Skin 500 mSv 150 mSv 50 mSv

Classified workers

This is anyone who is likely to receive:

  • Effective dose of > 6 mSv in a year (3/10 of dose limit)
  • Equivalent dose of greater than 3/10 of any dose limit i.e.
    • > 15 mSv/yr to lens
    • > 150 mSv/yr to skin or extremities


Classified workers must:

  • Must have a medical examination before being designated
  • Must have periodic review of health at least once a year
  • Must be at least 18 years old
  • Records of doses received by classified workers must be kept until the person has, or would have, reached 75 years old and at least 30 years from when the record was made

Designation of special areas

Controlled areas

  • Any person working in the area is likely to receive an effective dose of > 6 mSv, 15 mSv to the lens, or equivalent dose of > 3/10 of any relevant dose limit
  • External dose rate exceeds 7.5 micro Sv/h over a working day
  • Dose rate less than 7.5 micro Sv/h when averaged over a working day BUT the instantaneous dose rate at any point exceeds 100 micro Sv/h
  • Any person who enters or works in area must follow special procedures to restrict significant exposure

Supervised areas

  • Required if anyone working in the area is likely to receive a dose > 1 mSv/yr or an equivalent dose of > 1/10 of any relevant dose limit (i.e. more than the dose limits for the general public)

Reporting overexposure

In England, under IR(ME)R, any significant accidental or unintended exposures (SAUE) of patients should be reported to the Care Quality Commission (CQC). Where workers or members of the public are over-exposed with radiation the incidence is reported to the Health and Safety Executive (HSE) under IRR(17). The criteria for notification of patient doses are outlined in the following table (values for England only).

Accidental exposure


Exposure categoryCriteria for notification
All modalities including therapy

≥ 3 mSv effective dose (adult)

≥ 1 mSv effect dose (child)

Unintended exposure

Exposure categoryCriteria for notification
Intended dose < 0.3 mSv

≥ 3 mSv (adult)

≥ 1 mSv (child)

Intended dose 0.3 mSv to 2.5 mSv ≥ 10x more than intended
Intended dose 2.5 mSv to 10 mSv≥ 25 mSv
Intended dose > 10 mSv≥ 2.5x more than intended
Interventional / cardiologyWhere there has been no procedural failure AND either: the dose is ≥ 10x the local DRL OR there are observable deterministic effects excluding transient erythem
Radiotherapy pre-treatment planning scansIf CT planning scan needs to be repeated twice to obtain appropriate data set (i.e. 3 scans in total including the intended scan)
Foetal – all modalitiesWhere there has been a failure in the procedure for making pregnancy enquiries AND the resultant foetal dose is 1 mGy or more
Breast feeding infant – nuclear medicine onlyWhere there has been a failure in procedure AND the resultant infant effective dose is ≥ 1 mSv


Values from IR(ME)R incident: notification codes, categories and criteria

Nuclear medicine department

IR(ME)R (MARS 78 now revoked)

  • Regulates administration of a radioactive substance
  • Do not apply to substances that are naturally radioactive or administered for properties other than their radioactivity
  • Administration of Radioactive Substances (ARSAC) license granted to site or practitioner
    • Site license: whole scope of practice (diagnosis, therapy and research). Inidicative list of practioners
    • Practitioner license: for justification. Option to include research
  • Certificates are valid for 5 years and, following amendments, for a further 5 years

Environmental Permitting Regulations 2016

  • Governs storage and safe disposal of radioactive materials
  • Imposes requirements for traceability, record-keeping and contamination monitoring and security of radioactive sources
  • Regulated by the Environment Agency
  • Registration certificates are awarded to the sites of work, not individuals

Carriage of dangerous goods and use of transportable pressure equipment 2009

Govern the transport of radioactive substances by road


Britain, G., & Health and Safety Commission. (2018). Work with Ionising Radiation: Ionising Radiations Regulations 2017: Approved Code of Practice and Guidance. HSE books.

Desai, R., Brejza, P., & Cremona, J. (2004). The ionising radiation (medical exposure) regulations-IR (ME) R, Malta. World Journal of Nuclear Medicine3(suppl. 1), S107-S108.