The radiopharmaceuticals currently used for PET-CT examinations in China are approved by the national drug supervision department. The chemical amount contained in radiopharmaceuticals is generally minute and does not cause allergic reactions. Although radiopharmaceuticals contain radionuclides, the radiation dose is harmless or very small and within the acceptable range. The radiopharmaceuticals used for PET-CT examinations emit gamma rays, which have small biological effects in vivo and generally have a very short half-life. Under the premise of reasonable drug use, it is basically harmless to human body. Generally, the radiation dose received from one PET-CT examination is lower than that received from one chest X-ray, CT examination or coronary arteriography. Therefore, it is safe for patients, their relatives, society and the environment under the premise of reasonable clinical use and appropriate protection.