Guidelines for magnetic resonance diagnostic equipment in clinical use
This OC draws attention to a publication by the Medicines and Healthcare products Regulatory Agency on magnetic resonance imaging (MRI) equipment.
1. In 1993 the Department of Health's Medical Devices Directorate (which became Medicines and Healthcare products Regulatory Agency (MHRA)) published Guidelines for magnetic resonance equipment in clinical use, which deals with magnetic resonance imaging (MRI) equipment, making particular reference to safety. This was revised in 1997 and again in 2007 when it was republished as Device Bulletin DB2007(3) "Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use". HSE was consulted by the working groups that drafted these documents.
2. The guidelines were written primarily for healthcare, but are equally valid for other organisations using magnetic resonance diagnostic imaging equipment in clinical applications and will have some relevance to users of laboratory and veterinary magnetic resonance equipment.
3. The guidelines do not restrict themselves to the risks arising from static and time-varying magnetic and electromagnetic fields, but cover all hazards that may be present in MR suites, including noise, cryogens and oxygen depletion.
4. Warnings are included that people who have cardiac pacemakers should not enter the controlled area (where the permanently on, static magnetic field, B0, may exceed 0.5 mT) except on the advice and under the direct supervision of a registered medical practitioner. Other implanted medical devices, both active and passive, may be affected by the high magnetic fields (or radiofrequency emissions during image acquisition) and careful consideration should be given before allowing staff, patients and volunteers with implanted medical devices to enter the controlled area.
5. A precautionary approach is advocated for women in the first trimester of pregnancy, although there is no convincing evidence that electromagnetic fields arising in the normal mode of operation cause any detrimental effect to the well being of the embryo or foetus. Before pregnant workers are required to work in the controlled area, the employer should carry out a specific risk assessment analysing staff movement and location in relation to the magnetic fields and the possible duration of exposure (section 2.6.4). The decision whether a pregnant patient receives an MRI examination will need to be made by a suitably experienced and qualified medical practitioner.
Action by inspectors
6. Inspectors will find this document a useful reference prior to visiting clinical MRI facilities. They should ask as to whether the management of MRI suites is aware of it and whether they follow the guidance contained therein.