ECT is valuable for the diagnosis of diseases in all parts of the body. ECT imaging can reflect the functional changes of tissues caused by diseases, and can achieve accurate diagnosis by superimposing and overlapping the functional and anatomical images through image fusion technology. At present, it is most commonly used for the diagnosis of tumor and tumor metastasis, and has unique superiority for cerebral ischemic disease and epilepsy; for myocardial infarction and prognosis judgment, etc., it is a non-invasive examination method closest to the effect of catheterization. It also has important value for the diagnosis of endocrine system, urinary system, circulatory system and other diseases. ECT imaging is an important method for early diagnosis of bone metastasis of malignant tumors. In most cases, metastases can be detected early, and lesions are usually found earlier than conventional imaging. ECT imaging is now more and more widely used in the clinic, but it should be examined under the guidance of specialized doctors.