Medicines radiotracers used

Radiochemistry is defined as the chemical study of radioactive elements, both natural and artificial, and their use in the study of chemical processes (Random House Dictionary, 1984). Operationally, radiochemistry is defined by the activities of radiochemists, that is, (a) nuclear analytical methods, (b) the application of radionuclides in areas outside of chemistry, such as medicine, (c) the physics and chemistry of the radioelements, (d) the physics and chemistry of high-activity-level matter, and (e) radiotracer studies. We have dealt with several of these topics in Chapters 4, 13, 15, and 16. In this chapter, we will discuss the basic principles behind radiochemical techniques and some details of their application. 

Applications include the use of radionuclides in geo- and cosmochemistry, dating by nuclear methods, radioanalysis, the use of radiotracers in chemical research, Mossbauer spectrometry and related methods, the use of radionuclides in the life sciences, in particular in medicine, technical and industrial applications and investigations of the behaviour of natural and man-made radionuclides, in particular actinides and fission products, in the environment (geosphere and biosphere). Dosimetry and radiation protection are considered in the last chapter of the book. 

Medical science provides a framework or paradigm in which 10 understand disea.se and to maintain health. Nuclear medicine is the branch of medical science that contributes to medicine by the use of the radiotracer method for diagnosis and use of in vivo unsealed radioactivity for therapy. 

Some persons have thought that the increasing emphasis and development of positron-emitting radiotracers in nuclear medicine would result in a decrease in the development and use of single photon-emitting radiotracers. That this is not the case is illustrated hy the fact that there were 302 presentations involving technetium-99m at the June 2006 annual meeting of the Society of Nuclear Medicine in the United States. Iodine-123 accounted for 88 presentations, and indium-111 for 81. 

The uses of radioisotopes in medicine are extremely important. Certain elements are readily absorbed by particular organs in a human body, and this is capitalized upon in the use of radiotracers (introduced by food or drug intake) to probe the function of human organs. An advantage of the technique is that it is non-invasive. 

Radiotracers also have important uses in medicine. Iodine-131, for example, is commonly used to detect diseases associated with the thyroid gland. If a problem is suspected, the patient will drink a solution containing a small amount of iodine-131. After the iodine is absorbed, the amount of iodine taken up by the thyroid is measured and used to monitor the functioning of the thyroid gland. 

At the same time that new instruments, such as the Anger camera, were being invented, chemists were developing technetium-99m labeled tracers, based on the reduction of sodium pertechnetate to technetium-tin complexes, the latter being a more useful diemical form for labeling molecules. Radionuclide generators in which molybdenum-99 decayed to technetium-99m made radiotracers readily available in nuclear medicine clinics in hospitals. One after the other new tests were invented and soon put into clinical practice. 

Radiotracers are widely used in science, engineering, medicine, and particularly industry (IAEA 2004). They are required to be physically and chemically compatible with the process material under investigation. By injecting a radiotracer into the system, the material becomes labeled with radioactivity and the radiotracer follows the process material through the plant Eventually its subsequent movement can be monitored and recorded by external radiation detectors installed prior to the injection (Charlton 1986). Radiotracers must be relatively easily and cheaply produced by nuclear reactors and accelerators. Their ch ical form is also important to ensure that they remain in the intended medium throughout monitoring they need to be in the same phase as the process medium, either in aqueous or organic phase. 

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