Isotopes are atoms with the same number of protons but different numbers of neutrons from each other. Both stable and unstable isotopes exist, of which the latter shows characteristic radioactive decay through electromagnetism (gamma) or particle (α, β, Auger, etc.) emission.
Nuclear medicine includes imaging techniques single-photon emission computed tomography (SPECT) and positron emission tomography (PET), as well as therapeutic interventions brachytherapy, radioembolization and target-in radionuclide therapy (TIRT).Medical isotopes are also used for some types of external beam radiotherapy (EBRT) .Nuclear medicine physicians rely on the use of a dozen different isotopes that are matched to different applications based on their chemical and radioactive decay characteristics.
Radioisotopes can be separated and extracted from the treatment of waste liquid of nuclear reactors, accelerators, nuclear fuel and also can be prepared by means of generators, etc. Currently, more than 80% of medical radioisotopes are produced by research reactors. Other medical isotopes can be prepared by particle accelerators, mainly cyclotron, linear accelerator or other methods.
One of the main uses of medical isotopes is for diagnostic imaging procedures. Radioisotope, such as technetium -99m(99mTc), is a daughter isotope of 99Mo, which is an isotope used in medical imaging. When entering the patient's body for nuclear imaging, these medical radioisotopes can intuitively reflect the information of human molecular level, blood flow, function and metabolism, which is convenient for doctors to make early diagnosis of lesions that have not yet undergone morphological and structural changes.
Medical isotopes and generators under development：
Like other novel metallic radionuclides, copper 64 (64Cu) is currently being investigated as an alternative to gallium 68 (68Ga) and lutetium 177 (177Lu) radiopharmaceuticals, widely used to target somatostatin receptors expressed in neuroendocrine tumors (NETs) and prostate-specific membrane antigen (PSMA) expressed in prostate cancer cells. Due to the particularity of radionuclide 64Cu, it has aroused extensive interest among researchers, which also makes it almost an ideal example of thermal radiation radionuclide. In fact, 64Cu can simultaneously emit low-energy positrons β Particles and a bunch of Auger electrons. This different emission combination can not only be used to collect high-resolution PET images, but also can be used to stimulate the therapeutic effect. Another unique feature of 64Cu comes from the basic biological role of copper ions in organisms, where copper participates in a variety of cellular processes, including cell replication. The characteristic that copper participates in the physiological activities of the body makes us find that 64Cu, in its simplest ionic form Cu2+, can also specifically target a variety of cancer cells and be detected at the initial stage of its metastasis process.
89Zr is a new radionuclide, which plays an important role in immunopositron emission tomography (PET). The long half-life of 89Zr (t1/2=3.3 days) is helpful to evaluate the distribution of monoclonal antibodies in vivo. Therefore, 89Zr is expected to be used to monitor antibody based cancer therapy. Immune PET combines the sensitivity of PET with the specificity of antibody. In order to study the feasibility of 89Zr immuno PET imaging in predicting the efficacy of radioimmunotherapy and antibody therapy, imaging target expression, detecting target expression tumors, and monitoring anti-cancer chemotherapy, many studies have been carried out.
The radionuclide generator contains germanium (68Ge) as mother nuclide which decays to the daughter nuclide gallium (68Ga). The germanium (68Ge) used for the production of the (68Ge/68Ga) generator is carrier-free. The total radioactivity due to germanium (68Ge) and gamma-ray-emitting impurities is not more than 0.001%.
The generator is a system for the elution of gallium (68Ga) chloride solution for radiolabelling. This solution is eluted from a column on which the mother nuclide germanium (68Ge), parent of gallium (68Ga), is fixed. The system is shielded.
The technetium 99mTc generator is prepared with fission-produced molybdenum 99Mo adsorbed on alumina in a lead-shielded column and provides a means for obtaining sterile pyrogen-free solutions of sodium pertechnetate 99mTc Injection in sodium chloride.