Nuclear medicine includes 2 major parts: nuclear diagnosis and nuclear therapy. The main nuclear diagnostic tests are SPECT, PET and PET/CT imaging. So what diseases can nuclear medicine check? It can understand the function of major organs such as heart, kidney, liver, gallbladder, thyroid, 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. Doing different examinations to understand the different functional metabolic purposes use different varieties of radiopharmaceuticals, and there are very many kinds; and the labeled radionuclides are often very few.