Experimental investigation on workers' exposure to electromagnetic fields in proximity of magnetic resonance imaging systems

The paper presents the results of an experimental activity focused on the measurement of electromagnetic fields generated by magnetic resonance imaging systems, carried out with the purpose of assessing exposure of workers to static, low frequency and radio-frequency electromagnetic fields, as required by the EU Directive 2004/40/EC. The main contribution of the paper is that it presents a comparative study of exposure carried out during operation of the MRI system and close to the sources, with different scanning sequences and RF coils. Results show that the static magnetic field follows the theoretical values only close to the magnet due to the effect of the walls, with a few percent variation due to the operating conditions; exposure to the magnetic field in the low frequency band is mainly determined by emissions generated by the power grid at 50 Hz and by the pulses driving the gradient coils; and finally the radio-frequency band only shows contributions by the diagnostic pulses at the resonance frequency, with exposure levels usually below the limits contained in the Directive. (C) 2011 Elsevier Ltd. All rights reserved.