The UE directive 2004/40/EC and Magnetic Resonance Imaging a debate Thierry Metens Ph D Université Libre de Bruxelles, Hôpital Erasme Brain awareness week at the European Parliament

Magnetic resonance Imaging MRI Clinical MRI: strong C° evolution since early 1980's =>unique medical imaging progress worldwide > scanners & > 60M exams/year Brain MR: unequalled tissue resolution (T1, T2,  MTC,...) Emergency brain Imaging acute stroke, Diffusion MRI Brain structural connectivity: Nerve Tractography Brain activation: fMRI Brain metabolism: MRS WIP: Interventional procedures, brain peroperative MRI, MRI&FUS thermotherapy/drug delivery,... MRI Both clinical and scientific unique data

MRI: the technical ingredients Main Magnetic field (static) B0: T (earth ~ 50  T) Clinical Brain: 3.0T Pulsed Magnetic field Gradients:1KHz switching rate up to 60mT/m slew rate 200mT/m/ms Gradient field shielding Pulsed Radio frequency B1 field: B1 ~  MHz Non ionizing radiation Faraday Shielding

MRI: the technical ingredients Main Magnetic field: B0 field shielding => Strong B0 gradient Ferromagnetic objects attraction MAIN DANGER Transient Vertigo Pulsed Magnetic field Gradients: dB/dt Nerve stimulation, Induced currents in patient and in the close vicinity IEC Limits Pulsed Radio frequency B1 field: Patient tissue heating SAR IEC Limits

Includes any EM device: portable phone, Oven, MRI,...

Exposure limit values & Action values Conflict with MRI exposure limit values: limits on exposure to electromagnetic fields which are based directly on established health effects and biological considerations. Compliance with these limits will ensure that workers exposed to electromagnetic fields are protected against all known adverse health effects action values: the magnitude of directly measurable parameters, provided in terms of electric field strength (E), magnetic field strength (H), magnetic flux density (B) and power density (S), at which one or more of the specified measures in this Directive must be undertaken. Compliance with these values will ensure compliance with the relevant exposure limit values.

Exposure limit values & Action values Conflict with MRI Main Magnetic field: No ELV, AV 200mT clinical MRI 3 T Limit reached < 50 cm from magnet edge, Patient installation impossible (3T) Movement in B0: 1Hz, 40mA/m 2 head & trunk Exceeded <1m from magnet when v = 1m/s (Estimation < 500mA/m 2, factor 10) Patient installation impossible Pulsed Magnetic field Gradients: 1KHz 10mA/m 2 head & Trunk During Scan Exceeded <1m from magnet edge Patient critical monitoring (Anaesthesia, paediatric or IC patient) impossible interventional procedure impossible ( factor x 50) Pulsed Radio frequency B1 field: MHz ELV Whole Body 0.4W/Kg, Head&Trunk 10W/Kg, Limbs 20W/Kg, averaged over 6minutes Almost Never exceeded by Workers

The paradox MRI would have to be replaced in some instances by X ray procedures that have proven deleterious health effects on workers! The development of MRI could slow down, especially: High field ( >7T), Brain studies, Interventional & therapeutic Targeted drug delivery Alliance for MRI (UE MP, ESR, Scientific societies: statement & petition) The directive transposition has been postponed up to April 2012 ( 2008/46/EC)

New ICNIRP recommendations for MRI (2009) ICNIRP recommends also to take ferromagnetic object risk into account (nb: yet in the directive obligations of employers)

The debate The Directive is needed: Protection of Workers requires a legal frame The limits must be based on safe values from demonstrated adverse health effects, not on vague extrapolations or extreme precautionary values Studies should be undertaken in order to develop effective measurement devices to ensure limits are not exceeded in real life and to estimate possible MRI long term effects Propositions: Alliance = exemption/IEC limits? Modification of ELV/AV for MRI?

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