Radionuclides and radiopharmaceuticals

Table 2 lists a selection of radionuclides and radiopharmaceuticals used in radiotheraphy. 

Blower P J, Lewis J S, Zweit J (1996). Copper radionuclides and radiopharmaceuticals in nuclear medicine. Nucl. Med. Biol. 23 957-980. 

At all times the identity and amount of radionuclides and radiopharmaceuticals in the radiopharmacy department must be known. This also applies to the radioactive waste. All places where radioactive materials (including waste) are stored must be protected from fire and unauthorised access. 

The results obtained to date are considerable and show that the chemistry of the TcN group may well be the most varied and interesting of the transition metal nitrido complexes [1,9,10]. The aim of this chapter is to provide a fairly comprehensive review of the literature up to the latter part of 1994. Additional data may be found in two conference volumes [11,12] and a recent review of Tc coordination chemistry [4]. For macroscopic studies with the long-lived "Tc (ti/2 = 2.11 x 10s years) the "Tc radionuclide is denoted simply as Tc. No carrier added studies and radiopharmaceutical applications utilizing the shortlived "mTc radionuclide (ti/2 = 6.01 hours) are denoted as "mTc. 

Metals continue to play an important role in radiopharmaceuticals for diagnostic and therapeutic applications in nuclear medicine. Radiopharmaceuticals are drugs that contain a radionuclide and are used for imaging if the radionuclide is a photon emitter (gamma (7) or positron (/3+)) or for... 

The coordination chemistries of the elements considered in this chapter have already been the subject of detailed discussion in earlier sections of these volumes. Consequently, it is the purpose of this chapter to review, in general terms, the nuclear fuel cycle, the production of metal radionuclides and subsequently their incorporation into radiopharmaceutical formulations. Within this framework, specific aspects of coordination chemistry which are relevant to the application in question will be considered. 

Radiopharmaceuticals should have several specific characteristics that are a combination of the properties of the radionuclide used as the label and of the final radiopharmaceutical molecule itself. The radiopharmaceutical should ideally be easily produced (both the radionuclide and the unlabeled molecule) and readily available. The half-life of the radionuclide should be adequate to the diagnostic or therapeutic purpose for which it is designed. It has to be considered that radiopharmaceuticals disappear from the organism by a combination of two different processes. The biological half-life (showing the disappearance of a radiopharmaceutical from the body due to biological processes such as metabolization, excretion, etc.) and the physical half-life (due to the radioactive decay of the radionuclide). The combination of both parameters gives the effective half-life ... 

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. 

Positron emitting nuclides have very short half lives, on the order of minutes to tw o hours. This makes operation of a cyclotron and a radiochemistry laboratory essential to the use of PET scanners. is the longest radionuclide with a half-life of 1.87h, making a central production facility within a city feasible for radiopharmaceuticals employing this nuclide. Most clinical PET facilities have on-site cyclotrons and radiopharmaceutical laboratories to allow the use of short-lived isotopes in clinical studies. 

In order to be able to trace a specific biological process in the body, or investigate the functioning of a body organ, it is necessary to make a careful choice of both the radionuclide and the chemical form in which it is administered to the patient. Such radionuclide preparations are called radiopharmaceuticals. Today, some 100-300 radiopharmaceuticals are in routine use for diagnosis, most of which are commercially available. The majority of these compounds are organic in nature (see Table 4.6 for details). 

Identity and purity, stability, and sterility and apyrogenicity. The identity and purity of radiopharmaceuticals is verified by determining the radionuclidic and radiochemical purity. Stability concerns the radioactive label, which is related to radiochemical purity at a certain time after preparation. Since Tc pharmaceuticals are formulated as sterile, pyrogen-free solutions, the safety requirements of drugs for parenteral use do apply. Safe handling of the radionuclide is equally important and must comply with Euratom Directives, regulated by national law for radiation protection, which also concerns the application of radionuclides in adults and in children for diagnostic procedures. 

Sterile labeling units (kits) and closed systems offer flexibility for new synthetic concepts with radionuclides and play a major role in the production of short-lived radiopharmaceuticals. High labeling efficiency, short synthesis time, and high safety standards are excellent characteristics for routine production on site, where radiopharmaceuticals are administered. 

Radiochemical methods are primarily concerned with the study of radioactivity in naturally occurring radioactive materials and in other materials in which radionuclides and their compounds are produced by irradiation. The foundation of such studies is the careful measurement of radioactivity in a variety of environmental samples, food samples, radiopharmaceuticals, etc. Such measurement can be divided into two major types ... 

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