01 December 2002
Beware of flying objects
The most important component in a magnetic resonance imaging (MRI) system is the magnet. The magnet in a MRI system rates using the units of measure tesla and the gauss. One tesla equals 10,000 gauss.
Current MRI systems use magnets in the 0.5 to 2.0 tesla range, or 5,000 to 20,000 gauss. Magnetic fields greater than 2 tesla do not have approval for use in medical imaging. Powerful magnets on the order of 60 tesla do work in certain research areas.
The Earth's magnetic field, by comparison, rates at 0.5 gauss.
The MRI suite can be a very dangerous place. Metal objects can become dangerous projectiles if one takes them into the scan room. Paperclips, pens, keys, scissors, hemostats, stethoscopes, and other small objects can be pulled out of pockets and off the body without warning, at which point they fly toward the opening of the magnet-where the patient lies-at very high speeds.
MRI systems can erase credit cards, bank cards, or anything else with magnetic encoding. Those with pacemakers or residual shrapnel need not apply.