MRI Safety

Magnetic is resonance imaging is safe provided the basic MRI safety rule is respected: no object totally or partially made of metal can enter the room, excepted if professional MRI staff member has explicitely authorized it.

MRI is a powerfull magnet. Everybody who has ever played with small magnets or with a compass knows the force that magnetism can exert on ferromagnetic objects. The difference between these harmless objects and an MRI magnet is the order of magnitude of the magnetic field. The field which rotates the compass needle is the terrestrial magnetic field. Its value is about 30 µTesla which means 30/1,000,000 Tesla. The field strenght of current clinical MRI magnet is 3 Tesla, which means 100,000 times the strength of terrestrial the magnetic field! As 30 µTesla is sufficient to move the compass needle, you can imagine what an MRI magnet can do: transform any metallic (ferromagnetic) object into a dangerous projectile!

MRI Safety: Who to Screen ?

In order to avoid dangerous accidents, ALL the people who enter the MRI room should be screened, including:

• patients
• medical staff
• volunteers for research experiments
• accompanying parent/friend
• technical / cleaning / security staff

In most of the cases, the danger does not come from the patient himself, who is carefully screened, but from all the other people who enter the MRI environment.

MRI Safety: What to Screen ?

External objects:

• keys, mobile phone, wallet, credit cards, coins,...
• tools, machines,...

Internal objects:

• pacemakers
• should be described to the technologist before entering the MRI room: clips, electrodes,...
• metallic particles in the eyes