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IAEA Safety Standards and medical exposure

» What is meant under ‘medical exposure’? 

Medical uses of ionizing radiation involves three categories of exposure:

  • Medical exposure that is ‘exposure incurred by patients* for the purposes of medical or dental diagnosis or treatment; by carers and comforters; and by volunteers subject to exposure as part of a programme of biomedical research; 
  • Occupational exposure for those involved in the performance of radiological procedures; 
  • Public exposure for members of the public, such as in waiting rooms. 

*A patient is an individual who is a recipient of services of health care professionals and/or their agents that are directed at (a) promotion of health; (b) prevention of illness and injury; (c) monitoring of health; (d) maintaining health; and (e) medical treatment of diseases, disorders and injuries in order to achieve a cure or, failing that, optimum comfort and function. Some asymptomatic individuals are included. For the purpose of the requirements on medical exposure in the IAEA safety standards, the term ‘patient’ refers only to those individuals undergoing radiological procedures.

The requirements for radiation protection and safety differ according to the category of exposure, so it is important that the exposure of persons is categorized correctly. For example, a nurse assisting with image guided interventional procedures would be considered to be occupationally exposed, whereas a nurse working in an inpatient ward where occasional mobile radiography is performed by a medical radiation technologist would not be considered to be occupationally exposed but rather as subject to public exposure.

The term ‘carer and comforter’ has been introduced into GSR Part 3 to cover those persons who, outside an occupational capacity, willingly and voluntarily help in the care, support and comfort of a patient undergoing a radiological procedure. Carers and comforters are subject to medical exposure, whereas a casual acquaintance visiting a patient who has undergone radionuclide therapy would be considered a member of the public and hence subject to public exposure.

» How are radiation protection principles applied to medical exposure?

Medical exposure differs from occupational and public exposure in that persons (primarily patients) are deliberately, directly and knowingly exposed to radiation for their benefit. In medical exposure applying a ‘dose limit’ is inappropriate, as it may limit the benefit for the patient; consequently, only two of the radiation protection principles apply – justification and optimization.

The following table summarizes the radiation protection principles as applied to medical exposure in comparison with occupational exposure and public exposure:

Application to
medical exposure

Application to
occupational exposure
and public exposure

Justification: The diagnostic or therapeutic benefits of exposure are weighed against the radiation detriment they might cause, with account taken of the benefits and risks of available alternative techniques that do not involve medical exposure.

Justification of practices: Adopting a practice that entails exposure to radiation only if it yields sufficient benefit to the exposed individuals or to society to outweigh the radiation detriment.

Optimization of protection and safety: 

In diagnostic and interventional medical exposure, keeping the exposure of patients to the minimum necessary to achieve the required diagnostic or interventional objective.

In therapeutic medical exposure, keeping the exposure of normal tissue as low as reasonably achievable consistent with delivering the required dose to the planning target volume.

Optimization of protection and safety: Providing the best available protection and safety measures under the prevailing circumstances, so that the magnitudes and likelihood of exposures and the numbers of individuals exposed are as low as reasonably achievable, economic and social factors being taken into account.

Limitation of doses: Does not apply to medical exposure.

Limitation of doses: Doses to individuals are limited (for occupational exposure and public exposure).

» Who is responsible for applying Safety Standards?

There is a hierarchy of responsibilities within the framework for safety, from governments to regulatory bodies to the organizations responsible for, and the persons engaged in, activities involving radiation exposure. The government is responsible for the adoption within its national legal system of such legislation, regulations, and standards and measures as may be necessary to fulfil all its national and international obligations effectively. Specifically to medical exposure, the government has the responsibility to ensure that as a result of consultation between the health authority, relevant professional bodies and the regulatory body:

  • the relevant parties are authorized to assume their roles and responsibilities; 
  • a set of diagnostic reference levels is established for medical exposures incurred in medical imaging, including image guided interventional procedures; 
  • dose constraints are established for exposures of carers and comforters, and exposures due to diagnostic investigations of volunteers participating in a programme of biomedical research; 
  • criteria and guidelines are established for the release of patients who have undergone therapeutic radiological procedures using unsealed sources or patients who still retain implanted sealed sources. 

The prime responsibility for safety rests with the person or organization responsible for facilities and activities (hospital management). In the case of medical exposures, because of the medical setting in which such exposures occur, primary responsibility for protection and safety for patients lies with the health professional responsible for delivery of medical exposure. Only persons with the appropriate competencies are allowed to take particular roles and responsibilities; this applies in particular to persons undertaking the role of radiological medical practitioner, medical radiation technologist, or medical physicist. 

Other parties also bear certain responsibilities or can influence safety, e.g. suppliers of radiation generators and radioactive sources, technical standards associations, medical devices regulatory agencies, and health technology assessment agencies, health insurance or reimbursement companies and standards accreditation bodies. Government should be aware of these players in their country and utilize their influence to improve the practice of radiation protection and safety in medical uses of ionizing radiation.

» How can professional bodies contribute?

The collective term “Professional bodies” is used in GSR Part 3 to include the various organizations and groups of health professionals. These include societies, colleges, and associations of health professionals often within a particular specialty. 
Professional bodies represent the collective expertise of the given health profession and specialty and, as such, they also should play a role in contributing to radiation protection and safety in medical uses of ionizing radiation. 

Proactive involvement of the professional bodies in the process of establishing standards and regulations and in their application produces a number of benefits. Not only does it minimize the need for enforcement actions to ensure compliance, but also more importantly, it ensures a better understanding of radiation protection requirements and improves safety for patients. Professionals should be made aware of their responsibilities on the overall patient protection and safety in the referring to and during the delivery of medical exposure. This includes:

  • setting standards for education, training, qualifications and competence for a given specialty; 
  • development of referral guidelines for imaging (also called appropriateness criteria in some States) for use in justification of medical exposure for an individual patient; 
  • setting technical standards and giving guidance on practice, e.g. standards or norms that specify acceptable image quality; standards and guidelines for particular areas of the quality assurance programme; 
  • contribution to establishment of DRLs, dose constraints for carers and comforters and for volunteers in biomedical research; 
  • performing proactive risk assessment and encouraging their members to contribute to relevant international or national anonymous and voluntary safety reporting and learning systems; 
  • disseminating information on standards and guidance relevant to radiation protection and safety. 

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