Radiation protection of workers and the public in diagnostic and interventional radiology
Introduction
The medical use of X rays in diagnostic and interventional radiology remains a rapidly changing field, with a wide range of applications, procedures and techniques undertaken by the largest single group of workers occupationally exposed to artificial sources of radiation including physicians, medical physicists, technicians and nurses. Similarly members of the public also need to be protected against radiation while in a radiological facility.
The extent of occupational exposure of workers in radiological facilities depends on the type and complexity of the procedures employed, typically involving: interventional radiology, general radiography, computed tomography, fluoroscopy, mammography, and dentistry for example. For procedures with fixed installations, the staff members are generally adequately protected by well-designed shielding barriers and their occupational exposure is not significant. However workers in close proximity to the patient, for example physicians involved in fluoroscopy including interventional procedures, may be subject to considerable radiation dose. In these situations staff dose levels during their working life can in some cases lead to the occurrence of deterministic effects, such as cataract damage, if radiation protection actions are not utilised.
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.
The control of occupational exposure in diagnostic and interventional radiology is effectively utilised by: (i) design of facilities and imaging equipment including the, designation of workplaces as controlled and supervised areas, (ii) individual (personal) radiation monitoring, (iii) use of personal protective devices (lead lined aprons, leaded glass eyewear, thyroid shields, protective screens, etc.) (iv) reduction of the time when the worker is exposed to radiation and (v) by moving as far away from the source of radiation while still doing the required work actions. Essential for all these activities is education and training which is a prerequisite for the establishment of safe working procedures. There are many common factors that affect both patient and staff doses. It should be remembered that every action that reduces patient dose will also reduce staff dose, but the reverse is not true.
Public access to designated areas in hospitals and radiology rooms is restricted. Therefore radiation protection of the public will be efficiently achieved by necessary shielding and by safe working procedures that avoid directing of X ray tube towards areas with public occupancy.
Dose limits are introduced to ensure that the occupational exposure of any worker is controlled and below a certain dose per time period, as outlined in the International BSS. 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 to members of the public and workers.
In a number of situations the sick patient (commonly a child) may need the support of a family member (an attendant). In these situations the voluntary attendant is not considered a member of public and public dose limits do no apply to him/her. For such exposures dose constraints are defined by the ICRP and BSS. Such exposures are covered under medical exposure. The current value of dose constraint is 5 mSv per episode.
Important references
The Radiation Protection of Patients (RPoP) website contains information to help health professionals achieve safer use of radiation in medicine (radiology, interventional cardiology and other specialties and imaging modalities), including occupational and public exposure. This website also contains training material on radiation protection in diagnostic and interventional radiology and interventional cardiology, including for 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 radiology and other specialized areas are available for free download.