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The half-life is the time required for the initial concentration of a reactant to be halved. The measurement of the half-life is of great benefit in studies of the order of the reaction. For example, in first-order reactions, the half-life r1/2 is related to the rate constant k by the simple relationship The rate of radioactive decay does not depend on temperature. However, radioactive decay also follows a first-order kinetic equation. The half-life of a radioactive process can be determined by measuring the level of radioactivity at regular intervals and plotting the decay curve. Nuclear medicine (NM) is a medical specialty that uses radionuclides (radioactive “tracers”) and ionizing radiation for diagnostic and therapeutic (theranostic) purposes. NM arose and develops at the intersection of physics, chemistry and clinical medicine. The radiation emitted by radioactive isotopes may consist of gamma rays, beta and alpha particles, or a combination of both. The choice of a radioisotope for medical purposes is made in accordance with the following requirements: low radiotoxicity, suitable type of radioactive radiation, energy and half-life (from several minutes to several hours and days), and easy-to-detect gamma radiation. The radionuclide is a part of a radiopharmaceutical drug (RFLP) and acts as its marker. RFLP accumulates in anatomical structures, becomes a carrier of coordinated information from the patient to a gamma camera or other medical device, and reflects the dynamics of the processes occurring in the organ under study. In 2021, NM celebrates its 80th anniversary. The development trajectory of NM combines modern methods of radiotheranostics, including applied genomic and postgenomic technologies. Iodine-131, like some other radioactive isotopes of iodine (125I, 132I), are used in medicine for the diagnosis and treatment of certain thyroid diseases: • Treatment of diseases associated with hyperthyroidism: hyperthyroidism, diffuse toxic goiter (Graves' disease). • Treatment of certain types of thyroid cancer, detection of its metastases. To induce a euthyroid state in hyperthyroidism, the administered 131I activity is between 185 and 370 MBq. The isotope is used to diagnose the spread and radiation therapy of neuroblastoma, which is also capable of accumulating some iodine preparations. In Russia, pharmaceutical preparations based on 131I are produced by the Obninsk branch of the L. Ya. Karpov Research Institute of Physics and Chemistry. According to the radiation safety standards NRB-99/2009 adopted in Russia, discharge from the clinic of a patient treated with iodine-131 is allowed when the total activity of this nuclide in the patient's body decreases to a level of 0.4 GBq. Preparations: yobenguan-131. The half-life (8 days), on the one hand, is large enough for the nuclide to spread over large areas, and on the other hand, it is small enough to provide a very high specific activity of the isotope - about 4.5 PBq / g. жүктеу/скачать 119,35 Kb. Достарыңызбен бөлісу:
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