Radionuclides in The Life Sciences

The following fields of application of radionuclides in the life sciences can be distinguished ... 

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. 

Many organic molecules are large enough to form colloids, and organic colloids are frequently encountered in the life sciences. Humic substances are found in natural waters and may form complexes with radionuclides. 

The spectrum of radionuclides available for application in the life sciences broadened appreciably with the invention of the cyclotron by Lawrence in 1930 and the possibility of producing radionuclides on a large scale in nuclear reactors in the late 1940s. By application of T and C, important biochemical processes, such as photosynthesis in plants, could be elucidated. 

The largest field of application of radionuclides is in the life sciences. A survey is presented in Table 9.3. 

Radionuclidic purity is only of concern in the context of dual-isotope labeling, or if crosscontamination from a laboratory mishap is suspected. Radionuclidic purity is best measured by liquid scintillation counting modem LSC instruments have detectors and analysis software designed to discriminate quantitatively between the different isotopes used in the life sciences, except at very low counting levels. Radionuclidic purity is entirely distinct from isotopic purity, or content, of compounds labeled with stable isotopes, such as deuterium or carbon-13. Such information may be very important to the utility of stable-labeled compounds such as internal standards for mass spectrometric quantitation assays. ... 

Labelled compounds have found broad application in various fields of science and technology. A great variety of labelled compounds are applied in nuclear medicine. The compounds are produced on a large scale as radiopharmaceuticals in cooperation with nuclear medicine, mainly for diagnostic purposes and sometimes also for therapeutic application. The study of metabolism by means of labelled compounds is of great importance in biology. More details on the application of radionuclides and labelled compounds in medicine and other areas of the life sciences will be given in chapter 19. 

Smith D, Thomas R, Anderson E. 1980. Respiratory-tract carcinogenesis induced by radionuclides in the Syrian hamster. In Sanders C, et al., eds. Pulmonary toxicology of respirable particles. 19th Hanford Life Sciences Symposium, Richland, WA. Technical Information Center, U.S. Department of Energy, Springfield, VA. 

These radionuclides can be used for investigating the behavior of various radionuclides simultaneously in material and life sciences (the so-called multi-... 

Application of radionuclides in life sciences is of the greatest importance, and the largest single user of radionuclides is nuclear medicine. Shortly after the discovery of Ra in 1898 by Marie Curie and its subsequent isolation from pitchblende in amounts of 0.1 to 1 g, the finding that this element was useful as a radiation source led to the first application of radionuclides in medicine. In 1921, de Hevesy investigated the metabolism of lead in plants by use of natural radioisotopes of Pb. 

Boecker BB, Hahn FF, Cuddihy RG, et al. 1983. Is the human nasal cavity at risk from inhaled radionuclides In Thompson RC, Mahaffey JA, ed. Life-span radiation effects studies in animals What can they tell us Proceedings of the twenty-second Hanford life science symposium held at Richland, Washington, September 27-29, 1983. Hanford Life Sciences Symposium 22nd. Springfield, VA United States Department of Energy, 564-577. 

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. 

No general statement can be made about the elements that can be determined and the samples that can be analyzed, because these depend on the nuclear characteristics of the target nuclide (isotopic abundance), the nuclear reaction (cross-section and related parameters such as threshold energy and Coulomb barrier), and the radionuclide induced (half-life, radiation emitted, energy, and its intensity) for the analyte element, the possible interfering elements and the major components of the sample. CPAA can solve a number of important analytical problems in material science (e.g., determination of boron, carbon, nitrogen, and oxygen impurities in very pure materials such as copper or silicon) and environmental science (e.g., determination of the toxic elements cadmium, thallium, and lead in solid environmental samples). As these problems cannot be solved by NAA, CPAA and NAA are complementary to each other. 

Schematic representation of the logarithm of activity for a source containing the mixture of two radionuclides. Note that nuclide 1, due to its longer mean life, will survive nuclide 2, although Its Initial activity at t = 0 is much lower (10% of the total). This fact used to be the basis of the graphical decomposition of the decay curves of mixtures in the "pre-PC" age of nuclear science. The Idea for obtaining the A2W values (red line) from the thick (black) curve of the experimental A(t) values was to subtract the values of i(t) extrapolated back along the blue line representing the asymptote of the thick line for t 00...

In addition, radionuclide generators intended for applications in life science, in particular in the context of routine clinical use, must meet strict regulatory and quality control requirements. The production of the radionuclide generator parent, its separation from the target material, the chemical and technical construction of the separation of the radionuclide generator daughter are factors, which in totality shall finally result in an efficient and easy handling. They are discussed below. 

As a familiar example of the median in nuclear science, the half-life Tin of a radionuclide should be mentioned. (See Sect. 9.4.4 as well as the right-hand panels in Fig. 9.1.)... 

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