IEEE Committee on Man and Radiation (COMAR) Technical Information Statement "exposure of medical personnel to electromagnetic fields from open magnetic resonance imaging systems"

Open magnetic resonance imaging (MRI) systems enable performing image-guided medical procedures for long periods of time very close to, or inside, the patient imaging area. Medical personnel can be exposed to relatively high static, gradient, and radiofrequency fields compared to most other MRI systems. The Committee on Man and Radiation of the Institute of Electrical and Electronics Engineers calculated or used existing data on magnetic flux densities and field strengths in or near the patient area to assess occupational exposure levels. Potential exposures to each field type were analyzed and compared to relevant values specified in international exposure limits including those of the Institute of Electrical and Electronics Engineers and the International Commission on Nonionizing Radiation Protection. Exposures of the head or torso of a worker to gradient fields near the center of the patient-imaging area can exceed most exposure limits even for times less than a second. Exposures to radiofrequency fields can exceed limits if sustained exposures (minutes or more) occur to parts of the body. Static magnetic fields used by present Open MRI systems are below exposure limits of all of the standards that address these fields. Overall results of this study suggest that manufacturers and others who program or operate Open MRI systems should take care to ensure that operating parameters produce exposures that comply with the relevant exposure limits. Also, since field levels fall off rapidly with increasing distance, user practices may be implemented that reduce exposures significantly.