May 11 – 16, 2014
Casino Conference Centre
Europe/Prague timezone

Theoretical consideration of the specific activity of Tc-99m produced by the Mo-100(p,2n)Tc-99m reaction at cyclotrons

May 15, 2014, 5:30 PM
1h 15m
Gallery (Casino Conference Centre)


Casino Conference Centre

Reitenbergerova 4/95, Mari&#225;nsk&#233; L&#225;zn&#283;, Czech Republic <font color=white>
Poster Production and Application of Radionuclides Poster Session - Production and Application of Radionuclides


Bernhard Scholten (Forschungszentrum Jülich GmbH, Germany)


Even today the generator-produced radionuclide 99mTc is used for the vast majority of nuclear medical diagnoses. The parent radionuclide 99Mo is generally produced via fission of highly-enriched 235U, however, at a few nuclear reactor sites in the world only. Due to ageing reactors the world supply of fission-produced 99Mo has become somewhat insecure over the last few years. Alternative methods of direct production of 99mTc using accelerators are therefore presently attracting great attention. The (p,2n) reaction on highly enriched 100Mo appears to be the most promising one. Over the years several cross section measurements thereof have been reported. However, a critical analysis of the data and the influence of co-produced long-lived Tc-isotopes on the specific activity of 99mTc need to be critically considerated. From 100Mo the two long-lived radioisotopes 99gTc and 98Tcare co-produced. 99gTc is formed directly by the 100Mo(p,2n)99gTc reaction and indirectly via the decay of 99Mo and 99mTc during irradiation and after EOB. 98Tc is generated by the 100Mo(p,3n) reaction directly. We calculated excitation functions for the formation of 99Mo and 99mTc as well as for the long-lived technetium isotopes 99gTc and 98Tc by the code TALYS for the proton-induced reactions on 100Mo. For the first two nuclides calculations were also performed using the code STAPRE. The direct and indirect production of 99mTc was critically analysed. The integral yields of 99Mo, 99mTc, 99gTc and 98Tc were calculated for four chosen irradiation times as a function of proton energy. Therefore the activities of 99Mo and 99mTc as well as the number of atoms of 99mTc, 99gTc and 98Tc were deduced for six realistic proton energy ranges. The dependence of the specific activity of 99mTc was calculated in relation to energy range, irradiation and cooling time. The specific activity of 99mTc produced directly at a cyclotron was critically compared with that obtained from a fission 99Mo loaded generator. The long-lived isotopes 99gTc and 98Tc cause no significant radiation and mass dose to the patient but have a strong influence on the specific activity of the cyclotron produced 99mTc depending on the production conditions. At a suggested 22 MeV incident proton energy, for example, the ratio of long-lived Tc nuclei to 99mTc nuclei may far exceed 5.0, thereby possibly affecting the kit formulation of radiopharmaceuticals and also exceeding the limits set by radiopharmaceutical regulations, e.g. in Italy. Thus, detailed experimental and theoretical investigations related to the effect of a decreasing specific activity of 99mTc on the preparation of radiopharmaceuticals appear absolutely necessary.

Primary author

Bernhard Scholten (Forschungszentrum Jülich GmbH, Germany)


Arjan J. Koning (Nuclear Research and Consultancy Group,The Netherlands) Heinz H. Coenen (Forschungszentrum Jülich GmbH, Germany) Sandor Sudar (Debrecen University, Hungary) Syed M. Qaim (Forschungszentrum Jülich GmbH, Germany)

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