MRI of the brain is harmless to the human body, but there are certain side effects for special groups of people, as follows: 1. Patients who have undergone eye or cranial surgery can cause the displacement of metal substances present in the eye or cranial brain, resulting in damage to human structures or blindness, etc.; 2. Special types of work, such as welders and other people who have long-term contact with metal and iron filings, need to be carefully asked about their condition before the examination, or to exclude the residual metal substances in the cranial or maxillofacial area through X-ray films to ensure patient safety.