3. Magnetic shielding : MRI magnet stray field

SHIELDING THE MAGNETIC FIELD
OF AN MRI IMAGING SYSTEM

Designing the shielding of an hospital MRI room
Optimization of nature and thickness of the shield to comply with the 5 Gauss limit in the area open to the public

Case shown : protection of an open room on the floor above the MRI room
- MRI magnet : the magnet of the page example 2
- distance of the ceiling : 1.75 meter (5 ft and 9 in.) above the axis magnet
- shield set under the ceiling 

1- Schematic of an MRI room shielding

2- Bmodulus without shielding in the open room
the danger zone extend up to 3 Feet above the floor

3- B modulus 2D Map of the floor of the open room

4- Bmodulus with 4mm thick shielding on the ceiling of the MRI room
Material : magnetic (Fe-Si) steel (M15 type, US norm)
The open room is totally safe (B< 5 Gauss)

5- Bmodulus with 4mm thick shielding on the ceiling of the MRI room
Material : ordinary steel (low carbon)
The open room is partially unsafe (B > 5 Gauss in some area)