Nuclear medicine is a branch of medicine that uses radionuclides, that is, the various types of radiation they emit, to diagnose and treat disease. In vitro diagnostics is the radioimmunoassay technique, which is used to measure changes in the trace components of the body when a person is sick, and to assist clinicians in diagnosing and treating diseases. In vivo diagnosis, i.e. radionuclide imaging or nuclear medicine imaging (ECT), uses the difference in the distribution of radionuclide-labeled imaging agents in the human body under normal and abnormal physiological conditions to make a diagnosis. The amount of radiation given to the patient each time (i.e., the amount of light given to the patient) is equal to or less than that of a common X-ray examination, so it is very safe. Radionuclides are used to treat diseases in a similar way to imaging, i.e., the radiation emitted by the radioactive drug concentrated in the lesion area is used to destroy the diseased cells and thus to treat the disease. Nuclear medicine examination can understand the function of major organs such as heart, kidney, liver, gallbladder, thyroid gland, etc.; it can understand the blood perfusion of heart muscle, brain, lung and other organs; it can understand and determine the existence of tumor and lymphatic metastasis and bone metastasis, etc. All the functions, blood flow and metabolism of organs and tissues. Different tests are done to understand different functional and metabolic purposes using different kinds of radiopharmaceuticals, and there are often very few kinds of labeled radionuclides.