Carrying metal (except titanium) is absolutely strictly prohibited for MRI. Firstly, it may lead to the life of the examinee in danger, and secondly, it will damage the MRI machine and interfere with the imaging. 1. Hazard to the life of the examinee: There is a very strong magnetic field in the MRI machine and the MRI examination place, and the metal will move with the strong magnetic field, and it is forbidden to carry out MRI examination for the patients who have metal stents, metal clips, cardiac pacemakers, metal dentures, and metal sterilizers in their bodies. 2. Damage to the MRI machine: Metal may be sucked into the machine, damaging the machine and causing high repair costs. 3. Imaging interference: Since the composition of metal is completely different from the composition of the human body, it can lead to serious interference and formation of artifacts, which may affect the imaging of the target lesion. Currently, titanium/titanium alloys are not attracted to magnetic fields, so patients carrying medical instruments made of titanium can undergo MRI, but should inform their doctors beforehand.