PET-CT examination will cause some radiation to the human body, but the radiation dose is not very large. the radiation of PET-CT to the human body mainly comes from two parts, one is PET and the other is CT. the radiation of PET to the human body mainly refers to the radiation of the imaging agent taken by the patient during the examination, which usually does not exceed 10mSv. The radiation to the human body from CT is mainly the radiation to the human body from X-rays, which is usually between 10-20mSv. If the patient is using a low dose CT scan, it is usually below 10mSv. Therefore, the total radiation dose is usually around 20-30mSv and usually does not exceed 50mSv, while radiation doses below 50mSv are relatively safe for the human body.