Work-related factors associated with occupational exposure to static magnetic stray fields from MRI scanners

Purpose This study aims to identify work‐related and personal factors associated with workers' exposure to static magnetic fields (SMF) and motion‐induced time‐varying magnetic fields (TVMF) from MRI scanners. Methods Measurements of personal exposure to SMF and TVMF were performed among MRI staff during 439 work shifts at 14 different workplaces using portable magnetic field dosimeters. These data were coupled with contextual workplace and worker information. After data cleanup, 324 remaining observations were used to develop linear mixed effects models for various measures of peak and time‐weighted average (TWA) exposure. Results Exposure levels near whole‐body closed‐bore scanners increased by 30% to 76% for each additional tesla of scanner strength, depending on exposure metric. Small‐bore animal scanners, on the other hand, showed a reversed association with scanner strength. Measures of peak and TWA exposure were differently associated with specific tasks and scan procedures. In addition, body height of the worker was negatively associated with measured exposure levels. Conclusion The study revealed workplace characteristics, scan activities, and personal characteristics associated with SMF and TVMF exposure levels of MRI staff and was able to quantify the unique contribution of each of these factors while adjusting for the presence of others. Magn Reson Med 75:2141–2155, 2016. © 2015 Wiley Periodicals, Inc.