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Safety Standards

The current international requirements related to medical uses of ionizing radiation are established in the Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards (IAEA Safety Standards Series No. GSR Part 3). The full text of the publication in the official IAEA languages is available here.

1. Why have an international system of radiation protection?

While dealing with issues pertaining to radiation protection, the following situations could occur:

  • Some countries require a medical prescription to have radiation exposure for diagnosis, while other countries do not.
  • In some countries, whole body computed tomography screening is allowed, while in others it is not.
  • One country’s dose limit for occupational protection is 20mSv/yr, while another country prescribes 50 mSv/yr, etc.
  • In some countries, there is pressure to impose dose limits for patients undergoing medical examinations, while in others there are no dose limits for patients.
  • In some countries, patients who have received therapy with unsealed radiopharmaceuticals are sent home after a few hours, while other countries retain the patients in the hospital.
  • In some countries, those working with radiation enjoy certain privileges, while other countries do not allow privileges to replace radiation protection measures.

Such situations emphasize the need for credible international standards that are based on worldwide consensus.

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2. How are international standards on radiation protection achieved?

International Standards are a set of requirements agreed on by worldwide consensus, based on the knowledge of biological effects of radiation and on principles for protection from undesirable effects. The findings of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the recommendations of international expert bodies, notably the International Commission on Radiological Protection (ICRP), are taken into account in developing the IAEA safety standards.

  • Radiation effects: the Standards draw upon information derived from extensive research and development work by scientific and engineering organizations, at national and international levels, on the health effects of radiation and on techniques for the safe design and operation of radiation sources. They also draw upon the experience of many countries in the use of radiation and nuclear techniques. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), a body set up by the United Nations in 1955, compiles, assesses and disseminates information on the health effects of radiation and on levels of radiation exposure due to different sources..

  • Principles of protection: The principles for protection are obtained from the recommendations given by the International Commission on Radiological Protection (ICRP). The ICRP provides recommendations in a series of reports addressing general aspects of radiation protection and specific medical applications.

  • The IAEA safety standards: reflect an international consensus on what constitutes a high level of safety for protecting people and the environment from harmful effects of ionizing radiation. They are issued in the IAEA Safety Standards Series, which has three categories: Safety Fundamentals, Safety Requirements and Safety Guides.
    The current international requirements related to medical uses of ionizing radiation are established in the Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards (IAEA Safety Standards Series No. GSR Part 3).

The Standards place requirements on those authorized to conduct a practice using radiation, and are based on the presumption that there is a national infrastructure enabling Governments to discharge their responsibilities for protection and safety. It is this aspect that implicitly makes it necessary for international requirements to be established only by organizations with official status to establish these requirements. Which organizations fit into this slot? The official status accrues to international organization under the United Nation family. The IAEA is specifically authorized by its Member States, under the terms of its Statute to establish standards of safety for the protection of health and minimization of danger to life, in collaboration with the competent organs of the United Nations and the specialized agencies concerned and to provide for the application of these standards. Professional organizations can, however, collaborate and provide advice during the process of establishing and applying Standards.

The Standards have been developed with specific objectives to establish requirements for the protection of people and the environment from harmful effects of ionizing radiation and for the safety of radiation sources. The requirements have the force that is derived from the statutory provisions of the sponsoring organizations and further scope as contained therein.

Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards (IAEA Safety Standards Series No. GSR Part 3) is published in 2014. It is jointly sponsored by the European Commission (EC), the Food and Agriculture Organization of the United Nations (FAO), the IAEA, the International Labour Organization (ILO), the OECD Nuclear Energy Agency (OECD/NEA), the Pan American Health Organization (PAHO), the United Nations Environment Programme (UNEP) and the World Health Organization (WHO).

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3. What is meant under ‘medical exposure’?

Medical uses of ionizing radiation involves three categories of exposure [GSR Part 3]

  • 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.

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4. How radiation protection principles apply 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 summarises 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).

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5. 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 [GSR Part 3, Req. 2]. 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 [GSR Part 3, Req. 34]:

  • 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) [GSR Part 3, Req. 4]. 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.

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6. How can professional bodies contribute?

Professional bodies is the collective term 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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7. Who decides which medical procedure is appropriate and whether it is justified?

The process of justification allows determining whether the medical exposure will take place or not. The goal of justification is to avoid unnecessary radiological procedure, which would result in patient being unnecessary exposed to ionizing radiation and its potential risks. 

First, a given radiological procedure shall be justified. This applies to the justification of new technologies and techniques as they evolve. This generic justification shall be carried out by the health authority in conjunction with appropriate professional bodies. [GSR Part 3, para. 3.156]. 

The justification of medical exposure for an individual patient shall be carried out by means of consultation between the referring medical practitioner (who initiates the request for a radiological procedure) and the radiological medical practitioner (who is responsible for performing a procedure) [GSR Part 3, para. 3.157]. A referral should be regarded as a request for a professional consultation or opinion rather than an instruction or order to perform. The referring medical practitioner brings the knowledge of the medical context and the patient’s history to the decision process, while the radiological medical practitioner has the specialist expertise on the radiological procedure. Therefore, the joint approach is required to justification and shared decision at the level of an individual patient considering:

  • The appropriateness of the request;
  • The urgency of the procedure;
  • The characteristics of the exposure and of the individual patient;
  • The relevant information from any previous procedures;
  • The relevant referral guidelines.

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8. What guidance is available to help medical practitioners justify the individual patient exposure?

The process of determining appropriateness of a medical procedure is an evidence based approach to choosing the best test for a given clinical scenario, with account taken of the diagnostic efficacy of the proposed radiological procedure as well as of alternative procedures that do not use ionizing radiation, for example, ultrasound, magnetic resonance imaging (MRI) or endoscopy. 

Useful tools to support this decision making process include national or international imaging referral guidelines developed by professional societies. Imaging referral guidelines can be disseminated or utilized through electronic requesting systems and clinical decision support tools or systems. It should be ensured that such systems correctly apply the regulatory requirements for justification, in particular with respect to roles and responsibilities. 

In determining the appropriateness of the radiological procedure for an individual patient, the following questions should be asked by the referring medical practitioner:

  • Has it been done already?
  • Is it needed?
  • Is it needed now?
  • Is this the best investigation to answer the clinical question?
  • Has the clinical problem been explained to the radiological medical practitioner?

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9. Are there requirements to justify exposures for health screening of population or exposures of humans for research?

Justification for radiological procedures to be performed as part of a health screening programme for asymptomatic populations shall be carried out by the health authority in conjunction with appropriate professional bodies [GSR Part 3, Para 3.159]. 

Any radiological procedure on an asymptomatic individual that is intended to be performed for the early detection of disease, but not as part of an approved health screening programme, shall require specific justification for that individual by the radiological medical practitioner and the referring medical practitioner, in accordance with the guidelines of relevant professional bodies or the health authority. As part of this process, the individual shall be informed in advance of the expected benefits, risks and limitations of the radiological procedure [GSR Part 3, para 3.160]. 

The medical exposure of volunteers as part of a programme of biomedical research is deemed to be not justified unless [GSR Part 3, para 3.161]: 
(a) It is in accordance with the provisions of the Helsinki Declaration [3] and takes into account the guidelines published by the Council for International Organizations of Medical Sciences [4], together with the recommendations of the ICRP [5]; (b) It is subject to approval by an ethics committee (or other institutional body that has been assigned functions similar to those of an ethics committee by the relevant authority), subject to any dose constraints that may be specified, and subject to applicable national regulations and local regulations.

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10. How optimization of medical exposure is ensured and who is responsible?

Once justified, the radiological procedure should be optimized and performed such that the exposure of the patient is managed in order to achieve the medical objective. Too low a radiation dose could be as bad as too high a radiation dose, in that the consequence could be that a cancer is not cured or the images taken are not of suitable diagnostic quality. The medical exposure should always lead to the required clinical outcome. Optimization is a prospective and iterative process that requires judgements to be made using both qualitative and quantitative information. The following aspects and tools have to be used to ensure optimization of protection and safety [GSR Part 3, Req. 38]:

  • Appropriate design of medical radiological equipment and software;
  • Operational considerations specific to the modality and application;
  • Calibration of sources and dosimeters;
  • Quality assurance program implemented and independent audits made of this program;
  • Dosimetry of patients to determine typical doses to patients for common diagnostic and image guided interventional procedures, and absorbed doses to the planning target volume and relevant organs for each patient in radiotherapy;
  • Diagnostic reference levels established and used for most common diagnostic procedures (see more here);
  • Dose constraints used in the optimization of protection and safety for persons acting as carers or comforters, or subject to exposure as part of a programme of biomedical research.
Special considerations should be made for the optimization of protection and safety of patients who are:
  • pregnant or breast-feeding (see more here)
  • children (see more here)

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11. What is required for prevention and investigation of accidental medical exposure?

Unintended and accidental medical exposures can occur from flaws in design and operational failures of medical radiological equipment, from failures of and errors in software, or as a result of human error. The hospital management has responsibility to ensure that all practicable measures are taken to prevent such exposures, and, if such an exposure does occur, that it is properly investigated and corrective actions are taken [GSR Part 3, Req. 41]. Any of the following unintended or accidental medical exposures shall be promptly investigated and corrective actions implemented:

  • Any medical treatment delivered to the wrong individual or to the wrong tissue or organ of the patient, or using the wrong radiopharmaceutical, or with an activity, a dose or dose fractionation differing substantially from (over or under) the values prescribed by the radiological medical practitioner, or that could lead to unduly severe secondary effects;
  • Any diagnostic radiological procedure or image guided interventional procedure in which the wrong individual or the wrong tissue or organ of the patient is subject to exposure;
  • Any exposure for diagnostic purposes that is substantially greater than was intended;
  • Any exposure arising from an image guided interventional procedure that is substantially greater than was intended;
  • Any inadvertent exposure of the embryo or fetus in the course of performing a radiological procedure;
  • Any failure of medical radiological equipment, failure of software or system failure, or accident, error, mishap or other unusual occurrence with the potential for subjecting the patient to a medical exposure that is substantially different from what was intended.
Written records shall be kept of all unintended and accidental medical exposures. The more significant events are required to be reported to the regulatory body, according to the national requirements. In addition to mandatory reporting for regulatory purposes, anonymous and voluntary safety reporting and learning systems like the IAEA SAFRON and SAFRAD can significantly contribute to enhanced radiation safety and quality in health care. Read more for:
  • Accidents prevention in radiotherapy here
  • Skin injuries from image guided interventional procedures here

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12. Who has the primary responsibility for ensuring overall radiological protection of patients?

Because of the medical setting in which medical exposures occur, primary responsibility for radiation protection and safety for patients lies with the health professional responsible for the radiological procedure, who is referred to in GSR Part 3 as the ‘radiological medical practitioner’. The term radiological medical practitioner is the generic term that GSR Part 3 uses to refer to a health professional with specialist education and training in medical uses of radiation, who is competent to perform independently or to oversee procedures involving medical exposure in a given specialty. Health professionals that could take on the role of the radiological medical practitioner, depending on the particular use of radiation and on the laws and regulations in a State, include radiologists, nuclear medicine physicians, radiation oncologists, cardiologists, orthopaedic surgeons, other specialist physicians, dentists, chiropractors and podiatrists.

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13. Is involvement of medical physicist required and for what purpose?

GSR Part 3 requires involvement of medical physicist who provides specialist expertise with respect to radiation protection of the patient. Medical physicist is a health professional with specialist education and training in the concepts and techniques of applying physics in medicine, and competent to practice independently in one or more of the subfields (specialties) of medical physics (e.g. diagnostic radiology, radiation therapy, nuclear medicine).

The medical physicist has responsibilities in the optimization of radiation protection and safety in medical exposures, including source calibration, clinical dosimetry, image quality and patient dose assessment, and physical aspects of the quality assurance programme, including medical radiological equipment acceptance and commissioning. The medical physicist is also likely to have responsibilities in providing radiation protection and safety training for health professionals. In addition, he or she may also perform the role of the radiation protection officer, whose responsibilities are primarily in occupational and public radiation protection.

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[1] Fundamental Safety Principles – Safety Fundamentals SF-1. IAEA, 2006
[2] Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards (IAEA Safety Standards Series No. GSR Part 3, IAEA, 2006
[3] WORLD MEDICAL ASSOCIATION, 18th World Medical Assembly, Helsinki, 1974, as amended by the 59th World Medical Assembly, Seoul (2008).
[4] COUNCIL FOR INTERNATIONAL ORGANIZATIONS OF MEDICAL SCIENCES, WORLD HEALTH ORGANIZATION, International Ethical Guidelines for Biomedical Research Involving Human Subjects, CIOMS, Geneva (2002).
[5] INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Radiological Protection in Biomedical Research, ICRP Publication 62, Pergamon Press, Oxford and New York (1991).

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