Radioactive technetium

As a nuclear reaction, the s process is relatively well understood, but the problem lies in identifying an astrophysical site for it and determining the relevant physical parameters, such as neutron flux, mean time separating two neutron captures, and temperature. It has been shown that the most propitious temperatures are those of helium fusion. Added to the fact that the surfaces of certain red giants are rich in s isotopes, such as radioactive technetium and barium, this observation confirms the idea that the s process may be related to helium fusion regions in stars. 

The image of a bone scan of a normal chest (posterior view). Radioactive technetium-99m is injected into the patient and is then concentrated in bones, allowing a physician to look for abnormalities such as might be caused by cancer. 

Radioactive elements have no stable isotopes. Among the natural elements, polonium (atomic number 84) and heavier ones are radioactive. Technetium with its atomic number 43 is the lightest of all elements having no stable isotopes. Another light such dementis 61 promethium. Technetium has 26 unstable and 11 metastable (isomer) isotopes, all radioactive [28.9]. Details of the three most long-lived isotopes and two metastable (m) isotopes, important for tracer work, are collected in Table 28.3. 

Inhaled CNTs are rapidly absorbed and passed into the blood of humans. In a study involving human volunteers, Technigas (an aerosol of radioactive technetium-labeled carbon NPs in the range of 5-1 Onm) was shown to rapidly diffuse into the human blood. The authors concluded that carbonaceous air pollution could impact cardiovascular morbidity and mortality [16]. 

Iron s reducing abilities also appear useful in removing radioactive technetium, a common pollutant at nuclear processing facilities. Iron also appears to be effective for removing nitrates from the soil. 

Many of the uranium fission fragments are radioactive. Of special interest are technetium-99 [14133-76-7] and iodine-129 [15046-84-1] having half-Hves of 2.13 X 10 yr and 1.7 x 10 yr, respectively. Data on all isotopes are found in Reference 6 (see also Radioisotopes). 

Several modes of waste management are available. The simplest is to dilute and disperse. This practice is adequate for the release of small amounts of radioactive material to the atmosphere or to a large body of water. Noble gases and slightly contaminated water from reactor operation are eligible for such treatment. A second technique is to hold the material for decay. This is appHcable to radionucHdes of short half-life such as the medical isotope technetium-9 9m = 6 h), the concentration of which becomes negligible in a week s holding period. The third and most common approach to waste... 

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). 

The isolation and identification of 4 radioactive elements in minute amounts took place at the turn of the century, and in each case the insight provided by the periodic classification into the predicted chemical properties of these elements proved invaluable. Marie Curie identified polonium in 1898 and, later in the same year working with Pierre Curie, isolated radium. Actinium followed in 1899 (A. Debierne) and the heaviest noble gas, radon, in 1900 (F. E. Dorn). Details will be found in later chapters which also recount the discoveries made in the present century of protactinium (O. Hahn and Lise Meitner, 1917), hafnium (D. Coster and G. von Hevesey, 1923), rhenium (W. Noddack, Ida Tacke and O. Berg, 1925), technetium (C. Perrier and E. Segre, 1937), francium (Marguerite Percy, 1939) and promethium (J. A. Marinsky, L. E. Glendenin and C. D. Coryell, 1945). 

Technetium isotopes also help tremendously in the diagnosis of breast cancer. A technetium complex preferentially binds to cancer cells, so if a patient has cancer, radioactivity imaging will reveal high levels of radioactivity from the cancerous tissues. The red spot in the image below marks the location of cancerous cells. 

All isotopes of technetium (Z = 43) are unstable, so the element is not found an Avhere in the Earth s crust. Its absence left a gap in the periodic table below manganese. The search for this missing element occupied researchers for many years. It was not until 1937 that the first samples of technetium were prepared in a nuclear reactor. In fact, technetium was the first element to be made artificially in the laboratory. To date, 21 radioactive isotopes of technetium have been identified, some of them requiring millions of years to decompose. 

C22-0008. There are no stable isotopes of technetium, but several radioactive isotopes can be prepared. 

For patients with melanomas that are at risk of spreading to the lymph nodes, a sentinel lymph node (SLN) biopsy is performed. The SLN, the first lymph node to receive lymph draining from the tumor, is identified by injecting a radioactive material, technetium-99m-labeled radiocolloids, and vital... 

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. 

The discovery of the elements 43 and 75 was reported by Noddack et al. in 1925, just seventy years ago. Although the presence of the element 75, rhenium, was confirmed later, the element 43, masurium, as they named it, could not be extracted from naturally occurring minerals. However, in the cyclotron-irradiated molybdenum deflector, Perrier and Segre found radioactivity ascribed to the element 43. This discovery in 1937 was established firmly on the basis of its chemical properties which were expected from the position between manganese and rhenium in the periodic table. However, ten years later in 1937, the new element was named technetium as the first artificially made element. 

It is necessary to pay attention to environmental radioactivity when peaceful applications of nuclear methods are developed for various fields of science and technology. The importance of technetium in environmental safety was socially recognized not so long ago. The Commission of the European Communities... 

A field experiment in a migration study of technetium in the form of TcOj was carried out by Landstrom et al. [64] who injected Tc and radioactive 82Br (non-sorbing tracer) in a highly permeable zone at a borehole. After 10 hours, breakthrough of the tracer was measured, but no retardation, i.e. no reduction of Tc, was observed in comparison with 82Br. 

Another type of ligand is the monoanionic, tridentate oxygen donor [(C5H4R)Co-(P(0)R R")3] (Lor), which has been used to prepare the complexes of technetium [37] and rhenium [38] [M03L] and [MOX2L] (X Cl, Br). These complexes are stable in organic solvents but hydrolyse slowly in water. In order to evaluate their usefulness in radioimmunotherapy, the corresponding compounds were also prepared with radioactive rhenium isotopes. 

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