PET-CT is not very harmful to the human body and is usually a safe, non-invasive imaging test. According to studies, PET-CT is relatively safe as the radiation dose of both add up to 10-21mSv, while the risk threshold for human body is 50-100mSv. PET-CT is called Positron Emission Tomography (PET-CT), a branch of nuclear medicine imaging. PET-CT is the perfect integration of PET and CT, with PET providing molecular aspects of the function and metabolism of the lesion, and CT providing the exact anatomical site, which occupies an extremely important position in molecular imaging. The safety of PET-CT is a very important issue. PET-CT, as an imaging device, is always concerned about the radiation dose and the amount of radiation output must be confirmed before the examination can be scanned. Although PET-CT has some radiation damage, with the development of modern medical technology and the continuous optimization of scanning protocols, the amount of radiation is small and the damage to the human body from PET-CT is negligible, and patients can be examined according to their condition without having to consider the danger of PET-CT to the human body.