RR570 - Assessment of electromagnetic fields around magnetic resonance imaging (MRI) equipment

This report describes the results of an investigation of operator exposure to static and switched­gradient fields from magnetic resonance imaging (MRI) systems. The project involves both computational modelling and the measurement of personal exposure using dedicated magnetic field dosemeters. The work was undertaken by Professor Stuart Crozier of the University of Queensland acting as an MCL consultant. The computational modelling has three strands: modelling of the static and switched­gradient magnetic fields from MRI systems with 1.5 T, 4T and 7T magnets; modelling of induced current densities and internal electric field strengths arising from motion through static field spatial gradients; modelling of induced current densities and internal electric field strengths from time­varying switched­gradient fields. Close to the ends of the three MRI systems modelled, relevant occupational exposure could be exceeded by movement through the static field, or directly by the switched­gradient fields. This project has shown that the MRI personal dosemeter is capable of indicating, in real­time, situations which might lead to exposure guidelines being exceeded. This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the prior written permission of the copyright owner.