MHRA MRI safety guidance: Review of
key changes and emerging issues David Grainger
In November 2014, seven years after the previous edition, the Medicines and Healthcare Products Regulatory Agency (MHRA) published the 4th edition of the magnetic resonance imaging (MRI) safety guidelines1
. MHRA now publishes only in electronic form to
minimise costs, make it easier to update the content and make it easier for the MRI community to access.
T
wo stories in the press at the time of its publication highlighted the need for continuous vigilance within the MRI department. In the first incident2
, a large oxygen cylinder was accidentally brought into the MRI room by an
untrained member of staff and was drawn to the scanner, trapping and seriously injuring two members of staff. This was compounded by the inability of the site to quench the system and release the trapped staff for four hours. It was found that the emergency quench button had been disabled at this site. The manufacturer subsequently launched a worldwide action to check functionality at all sites3
. A key message from this story
is the importance of ensuring all staff are aware of the hazards and that access to the scanner is controlled. In the second incident4
a patient’s knife flew out of his pocket and hit him in the eye causing an orbital
fracture. Patients should be screened for metallic items and changed into appropriate clothing provided by the MR unit before entering the room.
Key changes to the guidance External reference changes A number of reference documents had been updated since publication of the third edition, notably the Health Protection Agency’s Protection of Patients and Volunteers Undergoing MRI Procedures in 20085
Pregnant patients There is little evidence of harm from magnetic fields or noise and we now recommend scanning should be based on clinical criteria and completed in normal mode, whenever possible. In normal mode the scanner uses low magnetic fields and the risk of ill effect to the patient is minimised.
MR safety expert Notable changes are the renaming of ‘MR safety advisor’ to ‘MR safety expert’. This followed publications by EFOMP14
and IPEM in the UK15 and mirrors the case of ionising radiation where two levels, an officer level and an expert level, are required. , the
International Commission on Non-Ionising Radiation Protection’s (ICNIRP) amendment to its statement on MRI procedures in 20096
and IEC’s equipment standard for MRI systems – IEC 60601-2-33 edition 3.0 in -42-
Defined safety areas Comments received whilst drafting the new guidance showed a general dislike for the definitions and inconsistent use of ‘MR controlled area’ and ‘MR inner controlled area’ in the existing document. It is anticipated that the introduction of the term ‘MR controlled access area’, defined such that it contains the ‘MR environment’ and that access is controlled, will be clearer. The term ‘inner MR controlled area’ was
20107 . These recommendations have led to an increase in the upper field strength for normal mode scanning to 4 Tesla (T) from 2.5T.
Other documents that have changed and are referenced in the guidance include: • Guidelines on limits of exposure to static magnetic fields8
; • Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz)9 ; ; ;
• Guidelines for limiting exposure to electric fields induced by movement of the human body in a static magnetic field and by time-varying magnetic fields below 1 Hz10 • Safety in Magnetic Resonance Imaging11 • Guidance document on MR safe practices12 • Standard F2503-1313
; .
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