PET-CT examinations are usually performed with the radioactive isotope fluorine-18, and the dose of radioactive contrast agent injected into the patient is usually no more than 10 mCi at a dose of 0.1 mCi/kg, which means that the radiation dose for a whole-body PET-CT examination is 10-32 mSv, and the natural radiation dose received by each person is 1-3 mSv per year. Of course the content varies from place to place, which is equivalent to a normal person receiving a natural radiation dose of 30 years in about 1 hour, which is equivalent to standing for a day on the second day of the Fukushima nuclear power plant leak in Japan, so the radiation dose is not negligible. Therefore, it is not recommended to use this equipment for routine medical examinations.