Excitation functions for the cyclotron production of 99mTc and 99Mo

Excitation functions for the (100)Mo(p,2n)(99m)Tc, (100)Mo(p,pn)(99)Mo and (98)Mo(p,gamma)(99m)Tc nuclear reactions were determined using 97.4 and 99.5% isotopic enrichment of (100)Mo and (98)Mo, respectively. The irradiations were performed on three different cyclotrons with overlapping data points from 6 to 65 MeV. The optimum energy range for the (100)Mo(p,2n)(99m)Tc 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 (99m)Tc amounts to 11.2 mCi (415 MBq)/mu A h or 102.8 mCi (3804 MBq)/mu A at saturation. There is no serious radionuclidic impurity problem, Production of (99)Mo is not viable due to the low cross section (similar to 130 mb) over the proton energy range of 30 to 50 MeV. The (98)Mo(p,gamma)(99m)Tc reaction was found to have a cross section of <0.2 mb over the proton energy range studied. The earlier assignment of this reaction channel as a potential route for production of (99m)Tc with a medical cyclotron is refuted in this study. Countries that do not have access to fission molybdenum-99 for the (99)Mo-->(99m)Tc generator, could consider use of a > 17 MeV proton energy cyclotron for regional production of (99m)Tc. (C) 1999 Elsevier Science Ltd. All rights reserved.