When we walk into a hospital, we all know about internal medicine and surgery, as well as laboratory and radiology departments. But when it comes to nuclear medicine department, many people have not heard of it, and even some clinicians do not have in-depth understanding. Nuclear medicine is a discipline that uses drugs marked with radionuclides to diagnose and treat diseases, and is a symbol of hospital modernization and the applied science of nuclear technology in the field of medicine. Nuclear medicine is applicable to the examination and diagnosis of many diseases of the human body, and is also very effective in the treatment of some diseases. In developed countries, almost one out of every three patients who visit the hospital have to use the diagnosis and treatment methods of nuclear medicine. In China, nuclear medicine is still an emerging discipline, but it is developing very rapidly. In 1934, the Curies obtained radioactive radium by artificial means for the first time, which laid the foundation for the wide application of artificial radionuclides in medicine. In 1942, Fermi built the first atomic reactor, thus solving the problem of artificial preparation of radionuclides. Since then, with the rapid development and penetration of modern science and technology, such as electronic computer technology, nuclear electronics, cell hybridization technology, nuclear pharmacology, molecular biology, gas pedal miniaturization and automation, nuclear medicine has been accumulating experience, forming theories and maturing in the process of application, and gradually recognized as an indispensable and important discipline of medicine, which is one of the important symbols of medical modernization. The essence of nuclear medicine is the radionuclide tracer technology. Tracer technology is actually not new to everyone. For example, the tracer technique is used to observe the habits of wild animals, such as pandas, in nature. Scientists caught the wild panda, put a radio transmitter on it, people in the room through the instrument can detect the movements of the giant panda, that radio transmitter is a tracer. The tracer used for nuclear medicine examination is not a radio transmitter, but a radionuclide. The radionuclide is attached to some compound, and it becomes a radioactive drug, which is introduced into the body, and the medical staff can detect the distribution of that drug in the body through the instrument outside the body. If you want to know about the heart, you can attach a radionuclide to a drug that can gather in the heart, or you can attach a radionuclide to a pro-tumor drug if you want to find a tumor. Thus, using radionuclide tracer technology, the metabolism and function of each organ or tissue of the patient can be observed. Functions of nuclear medicine Nuclear medicine imaging is fundamentally different from radiological imaging and ultrasonography methods. Nuclear medicine imaging depends on the blood flow, cell function, cell number, metabolic activity and drainage of organs or tissues, and is a kind of functional metabolic imaging, thus it is more conducive to the early detection and accurate judgment of diseases. While CT and MR examinations mainly show the anatomical and morphological changes of organs or tissues with high resolution as their main feature, nuclear medicine can show the relevant information of diseases early from the functional metabolic changes of organs and tissues. Bone imaging is one of the most commonly used imaging examinations in nuclear medicine, which has a history of more than 30 years and accounts for one-third of the imaging nuclear medicine workload in general hospitals at home and abroad. It is a technique in which osteophilic radioactive drugs are injected into the body through a vein and then the whole body is imaged through special instruments and equipment. It can show the morphology of whole body bones more clearly, and it can reflect the blood supply and metabolism of bones, so it is of great value for the diagnosis of various bone diseases, such as tumor bone metastasis, and the observation of treatment effect. Nuclear myocardial perfusion imaging can help patients with symptoms such as discomfort, pain and breath-holding in the precordial region to accurately diagnose whether they have myocardial ischemia, with an accuracy rate of more than 90%. For patients with coronary artery disease, nuclear myocardial perfusion imaging can help determine their treatment plan and assess their prognosis and risk level. For example, if the patient’s myocardial perfusion imaging is essentially normal, drug therapy is preferred; if myocardial ischemia is present, coronary stenting or coronary artery bypass grafting should be performed, depending on the severity and location. Radionuclide therapy is the first and most widely used treatment for thyroid disease. 131 iodine is the most effective and preferred treatment for hyperthyroidism. The radiation biological effect causes damage and destruction of the thyroid cells, and some of the cells are necrotic and dissolved, thus achieving the purpose of treatment. Since the world’s first treatment of hyperthyroidism with 131 iodine, more than 1 million cases have been treated abroad and more than 100,000 cases have been treated in China. High-dose 131 iodine therapy is a necessary treatment route for patients with thyroid cancer. In addition, advanced malignant tumors are often accompanied by bone metastases, and about 50% of patients have limited or generalized pain. Although external radiation radiotherapy has obvious analgesic effect, it can do nothing for multiple foci and has many side effects. In recent years, the osteophilic radionuclide 89 strontium has been used to relieve the pain of bone metastases by the ionizing radiation effect of beta radiation emitted by it.