Excitation functions for the cyclotron production of Tc-99m and Mo-99

Excitation functions for the Mo-100(p,2n)Tc-99m, Mo-100(p,pn)Mo-99 and Mo-9 8(p,gamma)Tc-99m nuclear reactions were determined using 97.4 and 99.5% iso topic enrichment of Mo-100 and Mo-98, respectively. The irradiations were p erformed on three different cyclotrons with overlapping data points from 6 to 65 MeV. The optimum energy range for the Mo-100(p,2n)Tc-99m reaction is 22 --> 12 MeV with a peak at similar to 17 MeV and maximum cross section of similar to 200 mb, Over this energy range the production yield of Tc-99m a mounts to 11.2 mCi (415 MBq)/mu A h or 102.8 mCi (3804 MBq)/mu A at saturat ion. There is no serious radionuclidic impurity problem, Production of Mo-9 9 is not viable due to the low cross section (similar to 130 mb) over the p roton energy range of 30 to 50 MeV. The Mo-98(p,gamma)Tc-99m reaction was f ound to have a cross section of <0.2 mb over the proton energy range studie d. The earlier assignment of this reaction channel as a potential route for production of Tc-99m with a medical cyclotron is refuted in this study. Co untries that do not have access to fission molybdenum-99 for the Mo-99-->Tc -99m generator, could consider use of a > 17 MeV proton energy cyclotron fo r regional production of Tc-99m. (C) 1999 Elsevier Science Ltd. All rights reserved.