Magnetic Field Considerations

The magnetic field strength used in MRI is several thousand times that of the earths magnetic field! This field is three-dimensional; therefore, magnetic field precautions must be applied to areas on floors above and below the Magnet, as well as to the surrounding space on the same level.

Take the following precautions to prevent danger to persons and equipment:

  • Post WARNING signs outside the 5 gauss zone, alerting personnel with cardiac pacemakers, neurostimulators, and other biostimulation devices of the affect of the magnetic field on these devices.

  • Post WARNING signs at the termination point of the Magnet Cryogenic Vent, alerting personnel to the sudden discharge of freezing gases and small objects.

  • Post SECURITY signs on both sides of all doors leading into the Magnet Room, alerting personnel of high magnetic field and not to bring ferro-magnetic objects in the Magnet Room. Security signs will also indicate magnet field strength.

  • Do not bring ferro-magnetic objects (e.g., tools, pens, tape measures, steel-toe shoes, vacuum pumps, etc.) into the Magnet Room. Large metal objects must not be brought near the outside walls of the Magnet Room. To find out about specific equipment proximity limits refer to the specific Pre-Installation manual published for the system.

  • Many non-ferrous tools may exhibit some attractive force into the Magnet. When a tool is not in use it should be placed outside the Magnet's 5 gauss zone. Placing tools closer may allow them to be pulled into the magnet causing personal injury or equipment damage.

  • During some service operations, ferrous tools and parts may have to be carried into or out of the Magnet Room. Examples would be gradient cable crimpers, table dock, longitude drive motor, blower box, coldhead, etc. Extreme care must be taken to prevent these ferrous parts from being pulled into the Magnet. Two field personal should be on site any time a ferrous tool or part must be moved into or out of the Magnet Room. The part replacement procedure should be consulted prior to removing or replacing ferrous components. The correct tools should be used in full working condition prior to attempting ferrous parts replacement.

  • Analog watches (those with hands) and magnetic-coded credit cards can be destroyed if taken near the Magnet.

  • Magnetic tapes can be erased, recording heads magnetized, and camera shutters ruined by strong magnetic fields.

  • Use only non-magnetic gas cylinders and Dewars when transferring cryogens into an energized Magnet. All gas cylinders must be secured to a cart or wall to prevent falling whenever the protective cap is removed.