A magnetic resonance imaging (MRI) scanner contains very strong magnetic fields. If we are not careful enough, wheelchairs, beds and polishers may be pulled into it. 　　In 2001, a 6-year-old boy received an MRI examination at the Westchester Medical Center in New York State. He was having an examination after brain surgery, and the oxygen cylinder became empty. An anesthetist immediately brought him a new bottle of oxygen, without noticing that the cylinder was made of stainless steel. The cylinder flew out of his hands and hit the boy's brain. 　　Similar accidents occurred in a Taiwan hospital. When an escort took the patient to the MRI Room, the oxygen cylinder next to the patient's wheelchair flew up as he stepped into the MRI Room. The bottle was attracted by the magnetic fields produced by the MRI scanner, and many people there were shocked. Fortunately, no one was hurt; though it took great deal of labor to remove the cylinder from the MRI scanner. For this reason, the hospital has since prohibited escorts from accompanying patients to enter the MRI room, and the accident has become a good example in hospital safety education.