Medicine radioactive tracers

Technetium-99m coordination compounds are used very widely as noniavasive imaging tools (35) (see Imaging technology Radioactive tracers). Different coordination species concentrate ia different organs. Several of the [Tc O(chelate)2] types have been used. In fact, the large majority of nuclear medicine scans ia the United States are of technetium-99m complexes. Moreover, chiral transition-metal complexes have been used to probe nucleic acid stmcture (see Nucleic acids). For example, the two chiral isomers of tris(1,10-phenanthroline)mthenium (IT) [24162-09-2] (14) iateract differentiy with DNA. These compounds are enantioselective and provide an addition tool for DNA stmctural iaterpretation (36). 

Nuclear medicine scans Method of body imaging that uses a radioactive tracer material (e.g., technetium and gallium) to produce body images. For example, bone scans detect uptake and cellular activity in areas of inflammation. 

Fourth, they are difficult to measure in body fluids. There are very precise ways of measuring very small quantities, in plasma or urine, of almost all conventional medicines and this has made it possible to make the kinetic measurements we have been considering earlier. Some of the techniques for the big protein medicines are not as reliable. For example, one way of tracing a big molecule s progress through the body is to label it with a radioactive tracer. Biopharmaceuticals can be labelled with, for example, radio-iodine (Iodine-125) which can be counted in samples of plasma or urine. However as proteins are similar or identical to normal proteins they can be metabolised and the label can become part of a metabolite or another breakdown product. Counting the iodine radioactivity in this case will not be measuring the parent molecule alone. 

Medical x-rays provided one of the first applications of radioisotopes. In 1914, the wounded from World War 1 were pouring into Paris hospitals. Marie Curie converted a Renault car into the first mobile radiological unit and drove it from hospital to hospital. Radioisotopes are now widely used in medicine to diagnose, study, and treat illness. A physician can determine, for example, how and at what rate the thyroid gland takes up iodine by using iodine-131 as a radioactive tracer and cobalt-60 is used to kill rapidly growing cancer cells. 

Technetium-99 TcJ is used as a radioactive tracer in nuclear medicine. How many protons and neutrons does an atom of this material have The atomic number (the smaller of the two numbers) is 43. Therefore, a technetium atom has 43 protons. The mass number is 99. The mass number is equal to the sum of the number of protons plus the number of neutrons. Therefore, if we subtract the atomic number from the mass number, we find the number of neutrons. In this case the neutron number is 99-43 = 56. 

Radiation from radioactive nuclides is used to detect changes in density or other characteristics of materials, to promote chemical, physical, or biological changes, and to provide a source of thermal energy. Some radioactive materials find use in industry, research, and medicine as tracers for physical, chemical, and biological processes.58... 

A radioactive isotope (radioisotope) is an unstable isotope of an element that decays into a more stable isotope of the same element. They are of great use in medicine as tracers (to help monitor particular atoms in chemical and biological reactions) for the purpose of diagnosis (such as imaging) and treatment. Iodine (-131 and -123) and Technetium-99 are used for their short half-lives. 

Radioactive substances may be used in medicine as tracers, the quantities used in this case being merely sufficient to enable them to be detected, or as therapeutic agents, in which case the quantities employed and the... 

The use of cobalt radiation treatments for cancerous tumors was described in Example 26-3. Several other nuclides are used as radioactive tracers in medicine. Radioisotopes of an element have the same chemical properties as stable isotopes of the same element, so they can be used to label the presence of an element in compounds. A radiation detector can be used to follow the path of the element throughout the body. Modern computer-based techniques allow construction of an image of the area of the body where the radioisotope is concentrated. Salt solutions containing "iNa can be injected into the bloodstream to follow the flow of blood and locate obstructions in the circulatory system. Thallium-201 tends to concentrate in healthy heart tissue, whereas technetium-99 concentrates in abnormal heart tissue. The two can be used together to survey damage from heart disease. 

For many years, imaging with radioactive tracers was used exclusively for diagnosis. Recent applications have expanded to other areas of medicine. Imaging is now used extensively to guide surgery, assist in planning radiation therapy, and support the technique of angioplasty. 

The peaceful application of nuclear reactors after World War II initiated the production of large quantities of radionuclides, which were introduced to medicine for the investigation of human physiology and disease. The application of radioactive tracers for clinical diagnosis and therapy increased hy the year, resulting in the widespread use of radioisotopes in clinical procedures. 

Radioactive tracers used in medicine today provide information, and need to be judged by how reliably they provide this information. Some of the safeguards built into the drug review process by the FDA for regulating pharmaceuticals are not needed in the case of the mass of injected material used in radiopharmaceuticals. With radiopharmaceuticals, the criterion should be whether the information provided by the diagnostic procedure is valid and valuable. 

MAJOR USES Used in the production of medicine, battery grids, cable sheaths, insecticides, rodenticides radioactive tracer wood preservation. 

The use of labelled compounds in life sciences is extensive, in fact, the largest single user of radionuclides is medical science. It has been said that radioactive tracers have been of equal importance to medicine as the discovery of the microscope. Presently one out of ten hospitalized patients in the United States is admitted to some nuclear medical procedure. 

The rate of incorporation and discharge of radioactively labeled substances in the body provides a measure of the metabolism of healthy and of sick tissues. On medical patients this information is obtained by external measurements referred to as radioisotope scanning (RIS). Such scanning can yield information about a medical disorder much before it is observed by other means. Since the amount of radioactive tracer is very small, this technique is referred to as non-invasive. In hospitals the department of nuclear medicine is normally responsible for these investigations. 

The expanded use of the cyclotron in the late 1930s and of the nuclear reactor in the early 1940s made available a variety of radionuclides for potential applications in medicine. The field of nuclear medicine was founded with reactor-produced radioiodine for the diagnosis of thyroid dysfunction. Soon, other radioactive tracers. 

In an article in NUCLEONICS in 1966, Michel TerPogossian (Figs. 5.1-5.3) and 1 wrote, The most important radioactive tracer in biological research is reactor-produced carbon-14, but it has never been widely used in nuclear medicine. .. The use of these nuclides (Carbon-11, Nitrogen-13, Oxygen-15 and Fluorine-18) in biomedicine justifies the additional effort to prepare them locally at the laboratory or hospital that plans to use them. ... 

The term atomic medicine was used for decades after the end of World War II to describe the new field of medicine based on the use of radioactive tracers to examine the dynamic state of body constituents. 

Molecular imaging requires both the proper radioactive tracer and an instrument for imaging the tracer distribution witbin the living human body. Kuhl and Edwards (1963) were the first to describe tomography in nuclear medicine. Their invention preceded that of Houndsfield using x-ray transmission tomography (Figs. 6.2 and 6.3). 

Radioactive atoms that emit high-energy particles or photons let us keep track of molecules as they take part in chemical reactions. He called these molecules radioindicators. Today we call them radioactive tracers, or radiotracers. The tracer principle became the foundation of a new medical specialty, called atomic medicine, later being called nuclear medicine, and today called molecular imaging. 

Radioactive elements, especially carbon-14, were key products of the Manhattan Project, and could be produced in large quantities by the nuclear reactors. They would provide the world with new tools for chemical and biomedical research. Radioactive tracers were able to broadcast their presence as part of radiolabeled molecules as they defined the the stream of life. Being able to measure the chemical processes in every part of the body of living organisms made it possible for creative biological and medical scientists to provide a whole new approach to biochemistry and medicine. The radionuclides, chiefly carbon-14 and phosphorus-32, led the way. 

George Hevesy laid the foundation of nuclear medicine, the tracer principle. The emission of photons from radioactive atoms makes it possible to track molecules as they participate in chemical processes anywhere in the human body. Radioactive molecules emit photons that penetrate the body and can tell us what they are doing at all times. 

See, for example, (a) Radioactive tracers in biology, by M. D. Kamen. New York Academic Press, 1947 (b) The use of isotopes in medicine and biology (Symposium Report). Madison Univ. Wisconsin Press, 1948 (c) various articles in Nucleonics, 1948. 

Radioactive tracers have played and are still playing an extremely important role in the fields of biochemistry and other biological sciences. Their application to medicine is described in detail elsewhere (see Vol. 4). Even apart from medicine, the ways of application are too many to mention. Here, the historic study of photosynthesis by Calvin and coworkers is briefly described as the representative one, followed by a recent multitracer study. 

Radioactive isotopes are used as radioactive tracers in chemical analysis and medicine. Isotope dilution is one application of radioactive tracers in which the dilution of the tracer can be related to the original quantity of nonradioactive isotope. Neutron activation analysis is a method of analysis that depends on the conversion of elements to radioactive isotopes by neutron bombardment. 

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