EU LEGISLATION BY DR STEPHEN KEEVIL
The European Union EMF Directive and MRI:
is a solution in sight at last? For over eight years now, the medical imaging community in Europe has been campaigning to mitigate the impact of a piece of European Union (EU) legislation, the EMF Directive, on clinical practice and research in MRI.
At last a solution seems within reach, but it is threatened by political dead- lock and could yet slip away. This article explores the background to this issue, the rationale for the directive, its implications, and what is at stake in the final months of negotiation.
T
he objectives of the European Union (EU) include improvement and harmonisation of working con- ditions across member states.
It does this by adopting pieces of legislation, known as directives, which are binding on the governments of mem- ber states. Each member state is required to ‘transpose’ the directive into national law, failing which the government in question can be subject to legal action (‘infraction pro- ceedings’) in the European Court of Justice. In the period 2000-2006, directives were adopted relat-
ing to the protection of workers from a variety of ‘physical agents’ in the workplace: noise, vibration, artificial optical radiation, and electromagnetic fields (EMF). The EMF directive (directive 2004/40/EC), adopted in April 2004 with a transposition deadline of 30th April 2008, sets lim- its for occupational exposure to EMF [1]. The MRI community became aware of the directive in
2003, that is in the latter stages of the legislative process. It was quickly realised that it would have serious conse- quences for both clinical and research uses of MRI, for reasons that are explored in more detail below. A campaign was launched to lobby the European insti-
tutions to change the directive. After considerable effort and the publication of two research studies, the MRI com- munity’s argument about the impact of the directive was accepted. Late in 2007, the European Commission proposed postponement of the transposition deadline by four years to allow time for a solution to be found. In June 2011 the Com- mission proposed a new directive, in which MRI workers would be excluded from the exposure limits, but harmonised
Stephen Keevil, Ph.D.,Consultant Physicist, Department of Medical Physics, Guy’s and St Thomas’ NHS Foundation Trust; Reader in Medical Physics, Department of Biomedical Engineering, King’s College London, UK.
stephen.keevil@
kcl.ac.uk
8 DI EUROPE
safe working practices would be developed to ensure safety [2]. However, this has not yet been accepted by the Council of the EU and the European Parliament, and in April 2012 a further transposition delay of 18 months was announced.
THE AIM OF THE DIRECTIVE
The directive has the laudable aim of protecting workers from adverse effects of exposure to EMF in the frequency range up to 300 GHz. Over most of this frequency range the potential adverse effect is heating of body tissues, so setting limits is simply a matter of agreeing how much heating is acceptable. However, below about 100 kHz, physiological effects relate to excitation of nerve tissue, not heating. There are two well-understood phenomena: peripheral nerve stimulation (PNS) and magnetophosphenes. PNS occurs when nerves are excited by the electric
field induced by a time-varying magnetic field in the hundreds to thousands of hertz range, while magneto- phosphenes are flashes of light in the visual field caused by exposure to EMF in the tens of hertz range. Both effects have well-defined thresholds in terms of the EMF ampli- tude, with some biological variation.
continued on page 11
Static magnetic field Switched gradients
RF coil
FigUre 1. Sources of EMF exposure in MRI. APRIL/MAY 2012
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