Bruker AVANCE, User Manual

Page: 10 / 110

Safety
10 H157655_1_008
Figure 2.1: Stronger Stray Fields in Vertical Direction than in Horizontal Direction
The magnetic field may affect the operation of electronic medical implants such as
pacemakers, if exposed to fields greater than 5 Gauss. Medical implants such as aneurysm
clips, surgical clips or prostheses may also be attracted. Further care must be taken around
changing fields (e.g. pulsed gradient fields). Eddy currents could be generated in the implant
resulting in heat generation and/or unwanted torques.
Ensure that all loose ferromagnetic objects are outside the 5 Gauss (0.5 mT) field zone of
the magnet before the magnet is ramped to field. Human experience and reaction speed are
totally inadequate to cope with the extremely nonlinear forces the magnet exerts on iron
objects. Therefore no ferromagnetic objects should be allowed to enter the magnet room after
the magnet is energized.
2.2.1 Exclusion Zone
The Exclusion Zone is the area inside the magnet's 5 Gauss (0.5 mT) field line, extended in
all directions, including rooms above and below the magnet area.
Individuals with cardiac or other medically active implants must be prevented from entering
this area. The exclusion zone must be enforced with a combination of warning signs and
physical barriers.
2.2.2 Security Zone
The Security Zone is usually confined to the room that houses the magnet.
Ferromagnetic objects should not be allowed inside the security zone to prevent them from
becoming projectiles.