The mandate and work of ICRP Committee 3 on radiological protection in medicine

Abstract

The mandate of Committee 3 of the International Commission on Radiological Protection (ICRP) is concerned with the protection of persons and unborn children when ionising radiation is used in medical diagnosis, therapy, and biomedical research. Protection in veterinary medicine has been newly added to the mandate. Committee 3 develops recommendations and guidance in these areas. The most recent documents published by ICRP that relate to radiological protection in medicine are ‘Radiological protection in cone beam computed tomography’ (ICRP Publication 129) and ‘Radiological protection in ion beam radiotherapy’ (ICRP Publication 127). A report in cooperation with ICRP Committee 2 entitled ‘Radiation dose to patients from radiopharmaceuticals: a compendium of current information related to frequently used substances’ (ICRP Publication 128) has also been published. ‘Diagnostic reference levels in medical imaging’ (ICRP Publication 135), published in 2017, provides specific advice on the setting and use of diagnostic reference levels for diagnostic and interventional radiology, digital imaging, computed tomography, nuclear medicine, paediatrics, and multi-modality procedures. ‘Occupational radiological protection in interventional procedures’ was published in March 2018 as ICRP Publication 139. A document on radiological protection in therapy with radiopharmaceuticals is likely to be published in 2018. Work is in progress on several other topics, including appropriate use of effective dose in collaboration with the other ICRP committees, guidance for occupational radiological protection in brachytherapy, justification in medical imaging, and radiation doses to patients from radiopharmaceuticals (an update to ICRP Publication 128). Committee 3 is also considering the development of guidance on radiological protection in medicine related to individual radiosusceptibility, in collaboration with ICRP Committee 1.

1. MANDATE OF ICRP COMMITTEE 3 AND CURRENT MEMBERSHIP

Committee 3 of the International Commission on Radiological Protection (ICRP) develops recommendations and guidance for protection of patients, staff, and the public against radiation exposure when ionising radiation is used for medical diagnosis, therapy, or biomedical research. From the 2017–2021 term, Committee 5 has been disbanded, and its responsibilities have been re-assigned to the remaining four committees. As a result, Committee 3 now also has responsibility for protection in veterinary medicine.

For the 2017–2021 term, Committee 3 is composed of 15 members from 12 countries (http://www.icrp.org/icrp_group.asp?id=9), with expertise in different areas of radiological protection in medicine: medical physics, nuclear medicine, radiology (including several subspecialties within radiology), radiation oncology, and surgery. The members are Kimberly Applegate (Chair), Colin Martin (Vice-Chair), Madan Rehani (Secretary), Jamila Alsuwaidi, Lodewijk van Bladel, Michel Bourguignon, Marie-Claire Cantone, Sandor Demeter, Makoto Hosono, Keon Kang, Reinhard Loose, Josep Martí-Climent, Yantao Niu, William Small, and David Sutton. Over half of the members are new members, joining Committee 3 in 2017, and more information about the members is available on the ICRP website (http://www.icrp.org/icrp_group.asp?id=9). Committee 3 also has two emeritus members, Sören Mattsson and Marvin Rosenstein, who contribute actively to ongoing reports. A short public summary of the annual meetings of Committee 3 is available on the ICRP website.

ICRP maintains formal relations with other organisations with an interest in radiological protection through specific agreements, or by granting special liaison status to organisations whose work is relevant to the Commission’s mandate. Representatives from the World Health Organization (María Pérez) and the International Atomic Energy Agency (Ola Holmberg) attend Committee 3’s annual meetings.

International organisations and other stakeholders are encouraged to propose topics of interest for new publications. In addition, symposium participants may suggest topics to the Commission’s committees. The members of each committee review the proposals that are relevant to their committee’s area of responsibility, and evaluate the need to produce reports on specific topics. Each committee forwards its recommendations to ICRP’s Main Commission. These recommendations are subject to approval by the Main Commission.

Members of Committee 3 lead or participate in task groups and working parties on a wide range of topics within the medical field relating to protection of patients and staff. Publications are developed for specific techniques or areas of expertise to give focused guidance for particular staff groups. Ongoing collaborative task groups with ICRP Committee 2 develop dosimetric data for evaluation of patient exposures. Several projects will be moving forward in parallel at any one time, and this paper presents a summary of the work that Committee 3 has accomplished over the past 2 years, and describes its current work. Readers are also referred to a previous publication (Vañó et al., 2015, 2016).

2. RECENT PUBLICATIONS

The development of new equipment and techniques for medical diagnosis and treatment using ionising radiation has never advanced more rapidly than in this century. This, coupled with continual improvement in, and availability of, facilities to control radiation levels, creates a regular need for updated guidance. All ICRP committees develop reports giving guidance and recommendations on application of these techniques at regular intervals, and those issued by Committee 3 over the last 5 years are described below.

Publication 120. Radiological protection in cardiology (ICRP, 2013a). Complex percutaneous coronary interventions and cardiac electrophysiology procedures are associated with high radiation doses that can result in patient skin doses that are high enough to cause radiation injury. This publication provides guidance on methods to reduce patient radiation dose, training recommendations, and quality assurance programmes for those involved.

Publication 121. Radiological protection in paediatric diagnostic and interventional radiology (ICRP, 2013b). Paediatric patients have a greater risk of developing cancer than adults, and this publication provides guiding principles for clinicians and staff performing diagnostic imaging and interventional procedures for paediatric patients to encourage the standardisation of procedures, raise awareness of issues, and improve practices for the benefit of patients.

Publication 127. Radiological protection in ion beam radiotherapy (ICRP, 2014). Ion beams, such as protons and carbon ions, have a finite range in tissue, and this allows better dose distributions for treatment of tumour volumes to be achieved. Ion beam radiotherapy requires more complex planning and treatment systems than conventional radiotherapy. Guidance is given on techniques, training of staff, and quality assurance programmes to minimise unnecessary doses to normal tissue and keep radiation exposure of staff to a minimum.

Publication 128 (in cooperation with Committee 2). Radiation dose to patients from radiopharmaceuticals: a compendium of current information related to frequently used substances (ICRP, 2015a). This publication is a compilation and ‘transition’ document to facilitate the work of users of ICRP publications on radiopharmaceuticals until the new dose coefficients for the International Commission on Radiation Units and Measurements(ICRU)/ICRP reference computational phantoms for adults and children of various ages become available. The publication compiles current ICRP information relating to radiation doses to patients, including biokinetic models, biokinetic data, dose coefficients for organ and tissue absorbed doses, and effective dose for major radiopharmaceuticals based on the radiation protection guidance given in previous ICRP publications. This publication also includes new information for ⁸²Rb chloride, iodide (¹²³I, ¹²⁴I, ¹²⁵I, and ¹³¹I), and ¹²³I-labelled 2ß-carbomethoxy 3ß-(4-iodophenyl)-N-(3-fluoropropyl) nortropane. The data presented in this publication are intended for diagnostic nuclear medicine and not for therapeutic applications. The publication also includes annexes on special biokinetic and dosimetric models, and recommendations on breast-feeding interruptions.

Publication 129. Radiological protection in cone beam computed tomography (CBCT) (ICRP, 2015b). The objective of this publication is to provide guidance on radiological protection in the use of the new technology of CBCT. Systems are incorporated into radiotherapy linear accelerator treatment units, interventional radiology and cardiology equipment, and specialised units developed for dental imaging. The new applications of CBCT and the associated radiological protection issues are substantially different from those of conventional computed tomography (CT), and it is used widely by specialists who have limited training in radiological protection. The perception that CBCT involves lower doses was only true in initial applications. Thus, advice on appropriate use of CBCT needs to be made widely available. This publication provides recommendations on radiation dose management directed at different stakeholders, and covers principles of radiological protection, training, and quality assurance aspects. Advice on optimisation of protection when using CBCT equipment needs to be strengthened, particularly with respect to the use of newer features of the equipment. Manufacturers should standardise radiation dose displays on CBCT equipment to assist users in optimisation of protection and comparisons of performance. Additional challenges to radiological protection are introduced when CBCT-capable equipment is used for both fluoroscopy and CBCT during the same procedure. Standardised methods need to be established for tracking and reporting of patient radiation doses from these procedures.

Publication 135. Diagnostic reference levels in medical imaging (ICRP, 2017). The Commission first introduced the term ‘diagnostic reference level’ (DRL) in Publication 73 (ICRP, 1996). The concept was subsequently developed further, and practical guidance was provided in 2001 (ICRP, 2001b). DRLs have proven to be an effective tool that aids in optimisation of protection in medical exposure of patients for diagnostic and interventional procedures through helping to identify facilities where dose levels are generally higher, and types of examination for which dose levels at particular facilities are greater. However, with time, it has become evident that additional advice is needed to assist imaging centres in using the DRL process effectively to identify facilities where work to improve optimisation is required, and carrying through the process of optimisation. There are issues related to definitions of the terms used in previous guidance, determination of the values for DRLs, the appropriate interval for re-evaluating and updating these values, how DRLs should be used in clinical practice, methods for practical application of DRLs, and application of the DRL concept to newer imaging technologies. This publication is intended as a further source of information and guidance on these issues. The publication recommends practical dosimetric quantities for use in DRL measurements, and provides information on the use of DRLs for interventional procedures and paediatric imaging. It suggests modifications in the conduct of patient dose surveys that take advantage of automated reporting of radiation-dose-related quantities. Since there is potential to collect larger amounts of data through these methods, use of median values from dose distributions in local facilities is recommended for national collation to set DRLs and local comparisons to trigger optimisation. Once DRLs are established, it is important to include information in training programmes for healthcare workers. The target audience for this publication is national, regional, and local authorities; professional societies; facilities where ionising radiation is used for medical purposes; and responsible staff within these facilities.

3. WORK IN PROGRESS

The development and preparation of recommendations, advice, and guidance is an ongoing process, and Committee 3 is currently working on the following reports.

Working Party on Occupational Radiological Protection Issues in Interventional Procedures (Chair: P. Ortiz López). This report was posted on the ICRP website for public consultation in the first half of 2017, and the comments received have now been reviewed and the report amended accordingly. The report was published in March 2018 (after the Symposium) as Publication 139 (ICRP, 2018). The numbers of interventional procedures performed by radiologists, cardiologists, and clinicians in other specialties is steadily increasing. Moreover, these staff groups are more likely to approach or even exceed the revised dose limit for the lens of the eye, so further advice is needed on staff protection. The document provides guidance on personal dose monitoring strategies, methods, and options; radiation protection approaches; the use and testing of radiation protection garments; the development of a radiation protection programme; education and training; and quality assurance. The target audience is medical physicists and other healthcare professionals in charge of occupational protection, personnel working in dosimetry services, clinical applications support personnel, regulators, and others having an influence on the overall safety culture and on quality assurance and improvement. The report will also be useful to those engaged in training, and standardisation of equipment and procedures; those with responsibilities for occupational health; hospital managers and administrators responsible for providing financial support for protective purposes; and professional bodies (organisations of interventionalists, medical physicists, nurses, and radiographers).

Task Group 101 on Radiological Protection in Therapy with Radiopharmaceuticals [Chairs: Y. Yonekura and S. Mattsson (Committee 3 emeritus member)]. The review of this report by Committee 3 has been completed and a revised copy taking account of comments will be submitted to the Main Commission. It is expected that an initial full draft will be ready for public consultation in 2018. The use of radiopharmaceuticals for therapy is increasing for the treatment of various tumours using novel radionuclides, compounds, tracer molecules, and the application techniques. The goal of most radiation therapy, including therapy with radiopharmaceuticals, is to optimise the relationship between the probability of tumour control and normal tissue complications, although the classic use of ¹³¹I iodide for the treatment of benign thyroid diseases still has great clinical significance. This report aims to provide a framework for estimating dosimetry for novel treatment approaches, and identify those situations with unique aspects that should be considered. It also deals with radiation protection of staff delivering treatments for whom handling of radionuclides emitting high-energy beta particles can give high doses to the hands, if protection is not optimised.

Task Group 79 on the Use of Effective Dose as a Risk-related Radiological Protection Quantity (Chair: J.D. Harrison). This task group is led by Committee 2, with members from ICRP Committees 1, 2, 3, and 4. Committee 3 has contributed to chapters on calculation and use of effective dose with respect to medical exposures. Considering exposures incurred by patients during medical procedures, effective dose is of practical value for comparing: doses from different diagnostic examinations and interventional procedures; the use of similar technologies and procedures in different hospitals and countries; and the use of different technologies for the same medical examination. Effective doses are derived for a reference adult, so such comparisons are only valid if the representative patients or patient populations for which the effective doses are derived are similar with regard to age and sex. Although, as stated in the 2007 Recommendations (ICRP, 2007b), ‘… risk assessment for medical diagnosis and treatment … is best evaluated using appropriate risk values for the individual tissues at risk and for the age and sex distribution of the individuals undergoing the medical procedures’, since doses for most medical diagnostic procedures are small, the simple assessment of effective dose for a reference person allows valid comparisons to be made. As it represents a single dose quantity linked to biological effects of radiation, it has been useful in education of clinical staff and others about relative doses from different medical procedures.

Task Group 89 on Occupational Radiological Protection in Brachytherapy (Chair: L. Dauer). Task Group 89 is developing a report related specifically to radiological protection of staff in brachytherapy. Publications 97, 98, and 105 (ICRP, 2005a,b, 2007a) addressed radiological protection principles for patients, but there is a need for relevant and practical recommendations for radiological protection of staff in brachytherapy. The target audience is clinicians, staff, medical physicists, radiation protection officers, and regulatory authorities. It is expected that this document will assist in partially implementing several of the actions in the IAEA Bonn call-for-action.

Task Group 36 on Radiation Dose to Patients from Radiopharmaceuticals [Chairs: D. Nosske (Committee 2) and S. Mattsson (Committee 3 emeritus member)]. This is a standing task group of Committees 2 and 3. Task Group 36 has published a report (Publication 128; ICRP, 2015a) on radiation dose to patients from radiopharmaceuticals. It includes data compiled mainly from previous ICRP publications, with new information for several radionuclides. Work with the models for certain radiopharmaceuticals is ongoing, including biokinetic models for ¹¹C compound B and ¹¹C choline. There is also an analysis of published data on the results of ongoing clinical studies for the Alzheimer markers ¹⁸F flutemetamol and ¹⁸F florbetapir, for which the development of biokinetic models is planned.

Working Party on Justification in Medical Imaging (Chair: K. Åhlström-Riklund). Several organisations have produced or are preparing documents in the same field. This report is intended to give practical advice to reduce the number of unjustified examinations. The aim is to have content that has not been published elsewhere, and to avoid repetition of material already published on issues related to justification.

Working Party on Radiation Protection in Medicine in Relation to Individual Responses to Ionising Radiation [Chair: M. Bourguignon (Committee 3), in cooperation with Committee 1]. The working party discussed clarification of the concepts of radiosensitivity and radioesthesia. Radiosensitivity is expressed at high doses as early and late tissue reactions after radiotherapy that occur without any error in the delivery of the therapeutic dose. These tissue reactions are due to cell death and loss of reproductive capability. Radioesthesia is expressed at low doses as the development of stochastic effects (cancer) after: (1) multiple medical imaging examinations that result in a cumulative dose; or (2) radiotherapy, in areas of normal tissue that receive scatter from the treatment beam. The effect results from survival of cells with altered DNA due to genetic disorders or instabilities that contribute to alteration of the DNA damage response. Many tests are available in research laboratories to evaluate both radiosensitivity and radioesthesia. The two concepts should be addressed in subgroups of the populations concerned. The issue of ethics for medical exposures should also be addressed. Genetic mapping in medicine can be expected in the near future.

Working Party on an Internet Resource on Radiation Protection for Healthcare Providers (Chair: S. Demeter). This is an update of the ICRP web-based educational document entitled ‘Radiation and your patient: a guide for medical practitioners’ (ICRP, 2001a; free access: http://www.icrp.org/docs/Rad_for_GP_for_web.pdf). The goal is to create concise educational pieces that highlight and reflect what ICRP contributes to the issue. These were published in the proceedings of the Third International Symposium on the System of Radiological Protection (Demeter et al., 2016). These may be incorporated into the Commission’s ‘ICRPaedia’, a free, online resource (http://www.icrp.org/icrpaedia/toc.asp).

4. OTHER ACTIVITIES

4.1. Educational slides

Several sets of educational slides corresponding to the most recent publications of Committee 3 have been produced for use in training courses, and are available for free download (http://www.icrp.org/page.asp?id=35). These sets include educational slides for:

Publication 113 (Education and training in radiological protection) (ICRP, 2009).

Publication 117 (Fluoroscopically guided procedures) (ICRP, 2010).

Publication 120 (Radiological protection in cardiology) (ICRP, 2013a).

Publication 121 (Radiological protection in paediatrics) (ICRP, 2013b).

Publication 127 (Radiological protection in ion beam radiotherapy) (ICRP, 2014).

Publication 129 (Radiological protection in CBCT) (ICRP, 2015b).

4.2. Future topics under consideration

During the annual meetings of Committee 3, proposals for new topics to be considered as future work are discussed. The list of topics under consideration includes the following items.

Radiological protection aspects of daily imaging in radiotherapy.

Framework for optimisation for individual patients.

Dose quantities and units for imaging equipment (in cooperation with ICRU).

Protection of the lens of the eye and cardiovascular system: implications for medicine of Publication 118 (ICRP, 2012).

Overexposures and unintended exposures in diagnostic and interventional procedures. Liaising with the International Atomic Energy Agency and other international bodies on development of guidance documents.

Improving patient dosimetry and protection in high-dose imaging procedures (interventional procedures, CT).

Newer methods to improve image quality while reducing patient doses, including criteria for acceptable levels of image quality for clinical CT and digital imaging.

Use of ionising radiation in sports performance assessment.

With the inclusion of veterinary medicine under the umbrella of Committee 3, the need for guidance in this area will be considered.

5. SUGGESTIONS ON RESEARCH PRIORITIES

Topics considered as priorities for research are also discussed by Committee 3 during its annual meetings. At its meeting in November 2016, Committee 3 proposed a number of topics, as follows.

Improved radiological protection in medicine requires a better understanding of dosimetry and methods of protection of patients, staff, and the public.

Assessment of the lens of the eye, skin, and extremity doses and methods of protection is necessary to improve occupational protection in interventional and nuclear medicine procedures.

Lens of the eye, skin, and organ dose evaluation must be understood more fully to improve protection for patients who undergo CT and high-dose interventional procedures.

Dosimetric data are needed to help in the assessment of non-cancer effects (e.g. cardiovascular and cerebrovascular) in radiotherapy and high-dose imaging procedures.

Additional methods need to be developed, on a continuing basis, to reduce patient dose while maintaining diagnostic information.

6. CONCLUSIONS

Over the last few years, Committee 3 has produced an average of one publication per year to provide guidance for those working in medicine. Documents are at several stages of development currently, and will go forward for publication in the next 2 years. Decisions about which new topics should be taken forward to meet the needs of the medical community will be made at the Paris meeting.