[Technetium-99m production for use in nuclear medicine].
BACKGROUND
Technetium-99m is the most important radioisotope used in nuclear medicine. Its routine application is ensured by introduction of 99Mo/99mTc generators. This paper reviews the present status and perspectives of different types of generators. Novelties in the production of either 99Mo for generators or directly 99mTc by using accelerators are also included. PRODUCTION OF 99MO IN NUCLEAR REACTORS AND 99MO/99MTC TYPES OF GENERATORS: The main source of 99Mo is a nuclear reactor. Nuclear reaction 99Mo(n, gamma)99Mo is rather simple, but the main disadvantage is a low specific activity of 99Mo. For routine production the nuclear reaction 235U(n,f)99Mo is used. It gives high yields of 99Mo of very high specific activity. However, its main disadvantages are high costs and generation of large quantities of highly radioactive waste. Depending on the separation method several types of generators were developed. The predominant is the chromatographic generator based on fission-produced 99Mo. Due to the disadvantages of (n,f)99Mo production, the alternatives based on (n, gamma)99Mo were developed. However, sublimation (except low temperature sublimation) and extraction generators at the present stage have no perspective. Only gel generators are promising. PRODUCTION OF 99MO AND 99MTC IN ACCELERATORS: Several nuclear reactions are considered. 100Mo(gamma, n)99Mo gives 99Mo of low specific activity. So it could be used in production by sublimation generators. The reaction 100Mo(p,pn)99Mo was also investigated but it seems not to be suitable for routine production of 99Mo. 99mTc can be directly produced by 98Mo(p, gamma)99mTc and 100Mo(p,2n)99mTc nuclear reactions. It seems that the latter could serve as an auxilliary source of 99mTc.


CONCLUSIONS
At present chromatographic generators based on fission-produced 99Mo seem to have no real alternative. Gel and in lesser extent sublimation generators are prosperous, but still not suitable for large scale production of 99mTc. The accelerators offer good possibilities but a real alternative to fission 99Mo has not been found yet.
Vucina
J
J
Institut za nuklearne nauke Vinca, Laboratorija za radioizotope, 11001 Beograd, p.f.522.
D008982:Molybdenum; D009683:Nuclear Medicine; D009688:Nuclear Reactors; D010315:Particle Accelerators; D011868:Radioisotopes; D011876:Radionuclide Generators; D013667:Technetium
D011868:Radioisotopes; D013667:Technetium; D008982:Molybdenum