Magnetic shielding may be necessary to limit the fringe field of the MRI magnet at certain sites or to improve image quality by eliminating external influences due to, for example, ferro-magnetic masses.
For the safety of people in the general vicinity of an MRI magnet, a controlled area is usually declared as defined by the 0.5 mT (5 Gauss) line. Magnetic fields higher than 0.5 mT should not be exceeded in a public area. Barriers, access control doors, warning signs and facilities for the safe keeping of watches, credit cards and other magnetically sensitive objects must be provided.
Further reduction of the fringe fields to 0.1 mT or even 0.05 mT (less than 1 Gauss) may be necessary to safeguard the performance of sensitive equipment such as computer monitors, image amplifiers and other medical equipment, etc. or to satisfy local regulations. For comparison, the magnetic field strength of the earth is approximately 0.04 mT (0.4 Gauss).
IMEDCO has experience in calculating, simulating, designing, producing and installing magnetic shields up to 600 tons of iron mass.