The full name of MRI is nuclear magnetic resonance imaging technology, which is a biological magnetic spin imaging technology. It uses the characteristics of atomic nucleus spin motion to generate signals after being stimulated by radio frequency pulses in an external magnetic field. It is a physical phenomenon that uses a detector to detect and input into a computer, and then displays an image on the screen after processing and conversion. Since MRI is magnetic field imaging rather than X-rays, it is not radioactive, so it is harmless to the human body and is very safe. So far, there has been no report on the harm caused by the use of MRI in hospitals. MRI imaging is currently recognized as a safe, accurate, and non-invasive diagnostic method. There is no need to worry about MRI examinations. However, due to the existence of a strong magnetic field, if there are ferromagnetic foreign bodies in the human body for some reasons, such as metal internal fixation after fracture, femoral head replacement, metal contraceptive ring, etc., it may bring a series of corresponding hazards, such as internal fixation movement, loosening, heating, and image interference. Therefore, if there are magnetic foreign bodies in the body, it is usually not appropriate to do MRI examinations. At the same time, all metal objects on the body surface must be removed before the examination, and they cannot be brought into the MRI scanning room to avoid unnecessary injuries. These hazards can be avoided.