Generator-produced radionuclides

The development of PET radiopharmaceuticals labeled with generator-produced radionuclides has facilitated greater use of PET in clinical nuclear medicine. The 68Ge/68Ga parent/daughter pair is ideal as a source of PET radiopharmaceuticals as a result of the favorable half-lives of both the parent and daughter radionuclides (43-45). The 271 days half-life of the 68Ge parent... 

We envision several potential generator-produced radionuclide labels for cryptates (Table I). Fortunately, early evaluations can be performed more conveniently with longer-lived tracers that are commercially available. The cryptate complexes are conveniently formed from the metal in deionized water and the cryptand dissolved in water or methanol. The complexes form instantly upon... 

Generator-produced radionuclides are also introduced into compounds suitable for specific applications, in particular in medicine. For Instance, " TcOj eluted from a Mo/ Tc radionuclide generator can be introduced into organic compounds by various chemical procedures that can be performed by use of special kits which allow easy handling. 

Some radionuclides are available from generators, which makes them conveniently available for widespread clinical use. The life of the generator varies with the half life of the parent of the generator-produced radionuclide. 

Yano, Y. in "Radiopharmaceuticals from Generator-Produced Radionuclides", pp 117-125, IAEA, Vienna, 1970. 

Pp. 111-115 of Radiopharmaceuticals from Generator-Produced Radionuclides. Vienna International Atomic Energy Agency (1971). 26 17629... 

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. 

A cyclotron is required to be registered with the state since it produces radionuclides. A dedicated PET scanner may or may not be required to be registered in a state depending on the state s statutes on this matter. Many states require a certificate of need (CON) prior to the purchase of a PET scanner, a mobile PET, or a PET/CT scanner. A PET/CT scanner is required to be registered with the state because of the CT unit, since all states require registration of radiation-generating machines. 

Mo/ Tc generators produced for worldwide application have a sophisticated system for safe elution of the daughter radionuclide. The generator column is well shielded with lead, and the whole system must be adequately shielded to reduce radiation exposure of the operator to a permissible level (Fig. 5.1). 

Although experimental quantities of radionucUdes were generated in the eariy part of the twentieth cerrtrrry, it was not imtil World War II that anthropogenically produced radionuclides became widespread. The development of nuclear weapons resulted in atmospheric releases... 

The generator produced positron emitters find application mostly in PET studies at centers without a cyclotron. A discussion of generator preparation is beyond the scope of this article (for a detailed discussion, c O Chap. 40 in this Volume). Here a very brief account is given of the production of the two long-lived parent radionuclides concerned (cf. Qaim 1987 Qaim et al. 1993). 

Generator parent radionuclides are obtained from uranium fission products (i.e., Mo and °Sr) or as decay products from ( Th/ Ac), or are produced directly in nuclear reactors etc.) or at accelerators ( Rb, Zn, etc.). 

As a potential disadvantage of KOH-NH3 chemistry, the production of additional radionuclides in the primary coolant has to be mentioned. Thus, by an (n,p) reaction with considerable amounts of are generated. Several radionuclides are produced by neutron capture in the different potassium isotopes, the most important of them being (halflife 12.5 hours), which is a p emitter with an associated y energy of 1.5 MeV. During operation at rated power with a potassium concentration in the primary coolant of about 10 ppm, a steady-state activity concentration on the order of 10 to 50 GBq/Mg is produced. Due to its short halflife, this radionuclide does not pose any problems in refuelling operations likewise, because of its high solubility in water it does not form deposits on the... 

The Mo/ Tc generator consists of an alumina column in which Mo (a fission- or reactor-produced radionuclide) is adsorbed as Mo-molybdate. Mo decays 87% to " Tc, and a Tc-pertechnetate solution is easily obtained by eluting the column with sterile sahne solution. Tc-radiopharmaceuticals are then synthesized by adding the generator eluate to one of the many commercially available radiopharmaceutical kits. Because the parent radionuclide decays to " Tc with a half-life of 66 h, the Mo/ Tc generator can be used daily for up to 1 week. 

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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