Radionuclides medical applications

Technetium is a very suitable radionuclide for medical applications. Owing to its short half-life, radiation doses to the human organism are very low. The problems of protein labeling with technetium have been reviewed by several authors " . The following methods of technetium reduction are used in protein labeling by ascorbate aloneby ascorbate and Fe + by Fe"+ by Sn"+ 84.85,93-9S). trolytic reduction 84. ss). jjy gjjZ+.tartarate by Sn -citrate (Tab. 3). 

Nowadays, nuclear medicine has become an indispensible section of medical science, and the production of radionuclides and labelled compounds for application in nuclear medicine is an important branch of nuclear and radiochemistry. The development of radionuclide generators made short-lived radionuclides available at any time for medical application. New imaging devices, such as single photon emission tomography (SPET) and positron emission tomography (PET) made it possible to study local biochemical reactions and their kinetics in the living human body. 

Other accelerator-produced radionuclides are also used in nuclear medicine (Table 19.2). One of the most important radionuclides in this group is This radioisotope of iodine has more favourable properties than it emits only y radiation and its relatively short half-life is more appropriate for medical application. Its production is described in section 12.1. Suitable accelerators for the generation of protons of relatively high energy, and transport facilities, are needed. 

Medical applications External radiation sources (medical application of X rays or radionuclides) Diagnosis 1-lOmSv 0.1-1 mSv a 0.5 mSv/y... 

Internal radiation sources (medical application of radionuclides such as " Tc) Diagnosis 1-1000 mSv O.l-lOmSv a 0.02mSv/y... 

It is the purpose of this book to present the facts about the presence of radionuclides in nature. The use of technology can significantly modify the exposure to natural radiation. Among the human activities which should be considered in this context are (i) the electricity generation by coal-fired power plants, (ii) the use of phosphate fertilizers, and (iii) many consumer products. Man-made radioactivity has found many useful applications in everyday life. The best known are medical applications. The use of radionuclides and radioactivity in diagnosis and treatment of diseases is well established practice. 

There are assessments predicting the use of reverse osmosis for the processing of the wastes from medical application [36,37] and for the removal of caesium-137 from decontamination wastes after accident in the steel production factory [38]. RO is considered as a method for removal of radioactive pollutants from contaminated water (removal of Cs and °Sr) in the vicinity of atomic power plants [39], as well as for removal of small quantities of radionuclides ( Rn, Ra) from... 

The suitability of a radionuclide for a particular medical application will depend upon its availability in a radiochemically pure form, its nuclear properties and its chemical properties. In respect of the first of these considerations it is necessary to eliminate any extraneous radiation sources from a material destined for medical use. This need for very high radiochemical purity has a bearing on the means by which the radionuclide is produced. One potential method is by nuclear fission of a heavy element. This approach has the advant e that carrier free radioisotopes of high specific activity may be produced. However, because the process produces a complex mixture of FPs, painstaking separation and purification of the desired radionuclide will be necessary. The problem is simplified somewhat by using a pure target isotope to produce an FP which has rather unique properties. Thus fission produces which may be separated from the other FPs by virtue of its volatility. Fission in pure may also be used to prepare Mo in carrier free form, although contamination by Ru, I and Te was a problem in early... 

Table 5.1. Generator systems for medical application of short-lived radionuclides...

Yttrium, Y, is another radionuclide used in nuclear medicine its handling requires special attention because of (i) its short half-life (64 h) and (ii) its method of obtention. Indeed °Y is prepared from Sr therefore, the obtained compound is always contaminated by its parent species °Sr, an unacceptable side product for medical applications. The ligand (119) is very selective for the extraction of °Y over Sr + from aqueous solutions into chloroform by this method a highly pure (>99.9%) sample of °Y can be obtained <93ANC1350>. 

The technique of positron emission tomography (PET), developed for medical applications, offers also the capability to map flow distributions in geological layers. Conservative tracers, marked with a positron emitting radionuclid, can be used for hydrodynamic studies in soil columns. Suitable tracers for such studies are for example kali-umfluoride- or cobalthexacyanocomplex, marked with the positron emitting isotops F-18 and Co-58 respectivly. 

Radionuclides find applications in many fields. Their major use, however, is in medicine, in both diagnosis and therapy. The production of radionuclides is carried out using nuclear reactors as well as cyclotrons. The reactor produced radionuclides are generally neutron excess nuclides. They mostly decay by P emission. The cyclotron produced radionuclides, on the other hand, are often neutron deficient and decay mainly by EC or emission. They are especially suitable for diagnostic studies. The reactor production of radionuclides is described in Chap. 38 of this Volume this chapter treats radionuclide production with cyclotrons. It is worth pointing out that today more than 300 cyclotrons exist worldwide (cf. Directory of Cyclotrons, lAEA-DCRP/CD, 2004), many of them in hospitals they produce short-lived radionuclides for medical use. Thus, radionuclide production science and technology at cyclotrons has become a very important feature of modern nuclear medicine. 

The metallic radionuclides Ga and "ln form strong metal complexes and are of considerable medical interest. Both are produced via (p,2n) reactions, the former on Zn and the latter on "Cd. Targetry and chemical processing problems have been well studied. The medical applications are well documented. For production on a smaller scale, the (p,n) reactions on Zn and "Cd have also been utilized (c Tarkanyi et al. 1990,1994). 

Key Examples of Generator-Derived Therapeutic Radionuclides with Proven Medical Applications. 1961... 

Syed and Hosain (1975) proposed Sc as a positron-emitting radionuclide for studying bone disease with positron emission tomography. Due to the increasing medical applications... 

His research on the production and potential medical application of radionuclides continued at the Institute of Nuclear Chemistry, Research Centre Jiilich GmbH, Germany, from 1991-1996. In 1996 he was appointed a University Professor for Nuclear Chemistry at the Institute of Nuclear Chemistry, Johannes Gutenberg-University Mainz, Germany. His current research activities are focused on the development and evaluation of PET radiopharmaceuticals, including radionuclide generator-based radionuclides. 

The massive production of radionuclides (radioactive isotopes) by weapons and nuclear reactors since World War II has been accompanied by increasing concern about the effects of radioactivity upon health and the environment. As illustrated in Figure 4.15 and by the specific examples shown in Table 4.7, radionuclides are produced as fission products of heavy nuclei of such elements as uranium or plutonium and are also produced by the reaction of neutrons with stable nuclei. The ultimate disposition of radionuclides formed in large quantities as waste products in nuclear power generation poses challenges with regard to the widespread use of nuclear power. Artificially produced radionuclides are also widely used in industrial and medical applications, particularly as tracers. Radionuclides may enter aquatic systems from both artificial and natural sources, and their transport, reactions, and biological concentration in aquatic ecosystems can be a water pollution concern. 

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