PET-CT is a perfect fusion of PET and CT. PET-CT can diagnose tumors and other diseases at an early stage. As tumor cells are metabolically active, their ability to take up imaging is 2-10 times that of normal cells, so it has the role of early diagnosis of tumors.PET-CT is able to carry out localized diagnosis of epilepsy, determination of qualitative and recurrence of brain tumors, early diagnosis of dementia, early diagnosis of transient ischemia (TIA), and early diagnosis of cerebral infarction.PET-CT is also able to carry out early screening of tumors, especially the early screening of PET-CT can also be used for early screening of tumors, especially for early screening of lung cancer, which is of great significance.