Occupational exposure to electromagnetic fields in MRI facilities: a case study in Italy

The wide diffusion of Magnetic Resonance Imaging (MRI) in diagnostics and research, with a trend towards high field systems (3T and 7T), has raised the attention on the possible health and safety risks for MRI workers due to exposure to electromagnetic fields (EMF). Three different EMF sources are present in MRI systems: a strong static magnetic field; a low-frequency gradient magnetic field and a radio-frequency electromagnetic field; furthermore, operators moving in the magnet room experience a very low frequency "perceived" magnetic field, due to the inhomogeneity of the static field. While all MRI workers are exposed to static and perceived magnetic fields, only the staff present during the scan in particular situations (e.g. anesthesiologists in pediatric examinations) is exposed to all sources. This study describes an occupational survey conducted in Italy according to a protocol for exposure assessment that we developed in accordance with the 2010 guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). In the investigated practices, the most significant contribution to occupational exposure was due to the gradient field which, however, resulted compliant with the ICNIRP reference levels. For what concerns the movements in the static field, which are related to the possible onset of sensory effects such as nausea, dizziness and perception of magnetophosphenes, measured data were processed according to an original method, currently under revision following the new 2014 ICNIRP guidelines. Realistic operator movements have also been filmed and associated with the data. As a future development of this study, new measurement campaigns are being planned, in order to correlate the field levels with the sensory effects possibly experienced by the operators.