Radiation protection of workers and the public in nuclear medicine
Introduction
Nuclear medicine involves handling of radioactive materials that can give rise to external and internal exposure of staff. The magnitude of exposure depends on radionuclide, its activity and type of work within a department in which the person is involved. Relatively newer imaging modality that involves use of positron-emitting radionuclides for PET scanning has lead to the increased exposure of staff. Within the field of therapeutic application in nuclear medicine, new agents with beta emitters of higher therapeutic effectiveness have been used. In line with increasing number of medical procedures involving beta emitting radionuclides, extremity doses and possible skin contamination of nuclear medicine staff is of special concern.
The public can be exposed to radiation from a patient as external radiation emitted from the patient, internal contamination from radioactive body fluids and through multiple environmental pathways.
Radiation protection in nuclear medicine is concerned with the control of both normal and potential exposure of workers in all situations that involve use of unsealed sources of radiation.
Important Principles
The principles of the protection of workers from ionising radiation in all areas of medicine are directed at prevention of deterministic effects and minimization of risk for stochastic effects (cancer). These principles include use of dose limits for workers and general public and “As Low As Reasonably Achievable” (ALARA) principle to keep doses well below the dose limits.
The control of occupational exposure in nuclear medicine is effectively utilised by numerous actions as: design of facilities, designation of workplaces in control and supervised areas, individual monitoring arrangement, area monitoring, monitoring for contamination, use of personal protective devices and protective tools as appropriate, following the local rules and procedures for safe handling of radiopharmaceuticals and appropriate education and training. The principles apply to all situations that involve handling of unsealed sources of radiation and where in addition to external exposure, the contamination of staff and working environment may occur.
Public access to designated areas in hospitals and nuclear medicine departments is restricted and limited in terms of its duration. Radiation protection of the public will therefore be efficiently utilised by shielding of the radiation sources, proper design of a facility, access restriction and by safe working procedures followed by the staff members.
Dose limits are introduced to ensure that the occupational exposure of any worker is controlled and below a certain effective dose per time period, as outlined in the International BSS. In nuclear medicine, total dose includes both internal and external exposure to ionising radiation. The sources of exposure of the general public are primarily the same as for workers. However, based on the level of acceptable risk, different dose limits apply for members of the public than for workers.
In nuclear medicine it is common that family member(s) of the patient (attendants) need to look after the patient at home who has been administrated radioactivity. This is not restricted to children or seriously ill family members but may apply to any member of the family. Moreover proximity to radioactive patient during travel from hospital to home is also a source of radiation exposure to attendant. The attendant comes in category of individuals who voluntary support or comfort patients undergoing procedures that involve ionizing radiation exposure. Further details on radiation protection of general public are available at Radiation Protection of Patients (RPoP) website.
Important references
The Radiation Protection of Patients (RPoP) website contains information to help health professionals achieve safer use of radiation in nuclear medicine, also from the viewpoint of occupational and public exposure. This website also contains training material on radiation protection in nuclear medicine and radiation protection in PET/CT including specifically radiation protection of workers and the public.
The key standards in this area are the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources, also known as the International BSS. These standards mark the culmination of efforts that have continued over the past several decades towards the harmonization of radiation protection and safety standards internationally. Safety reports to guide users in applying safety standards in different areas of medical application of ionising radiation are available for free download.