PET-CT is a combination of CT and PET, which provides precise anatomical localization of the lesions by CT and detailed molecular information about the function and metabolism of the lesions by PET, which is sensitive, accurate, specific and precise in localization, etc. A single imaging can obtain tomographic images of the whole body in all directions, which can be used to understand the overall condition of the whole body and achieve the purpose of early detection and diagnosis of diseases. It can understand the overall condition of the whole body and achieve the purpose of early detection of lesions and diagnosis of diseases. The four important functions of PET are, firstly, early diagnosis and differential diagnosis of tumor, searching for primary and metastatic foci of tumor, guiding and determining the treatment plan of tumor, and evaluating the efficacy of treatment. Among tumor patients, after PET-CT examination, a considerable number of patients have changed their treatment plan due to clear diagnosis; after operation, it can identify whether the tumor has recurrence or not, stage and re-stage the tumor, monitor the tumor residue, and detect various kinds of radiotherapy, etc. PET-CT can accurately evaluate the therapeutic efficacy, adjust the treatment plan in time, and avoid ineffective treatment. Overall, it greatly saves medical costs and fights for valuable treatment time. Secondly, PET-CT can accurately localize epileptic foci and accurately determine the epileptogenic foci in the brain. After the guidance of PET-CT, surgical or γ-knife treatment is used, and very good therapeutic effect is received. PET-CT can identify whether the myocardium is alive or not, it can identify the degree of necrosis of the heart machine in detail, PET-CT can find out whether the myocardium is really "dead" or just dormant.PET-CT myocardial imaging is recognized as the "gold standard" for the evaluation of myocardial viability. PET-CT myocardial imaging is recognized as the "gold standard" for assessing myocardial viability. In addition, PET-CT is also the most effective means of health check, it can complete the whole body test in a single image, early detection of tumors and heart, brain diseases that seriously endanger people's health, to achieve the purpose of early treatment of disease and prevention of disease.
From the discovery of distant metastatic tumors have significance.