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

Abstract

Excitation functions for the 100Mo(p,2n) 99mTc, 100Mo(p,pn) 99Mo and 98Mo(p,γ) 99mTc nuclear reactions were determined using 97.4 and 99.5% isotopic enrichment of 100Mo and 98Mo, respectively. The irradiations were performed on three different cyclotrons with overlapping data points from 6 to 65 MeV. The optimum energy range for the 100Mo(p,2n) 99mTc reaction is 22→12 MeV with a peak at ∼17 MeV and maximum cross section of ∼200 mb. Over this energy range the production yield of 99mTc amounts to 11.2 mCi (415 MBq)/μA h or 102.8 mCi (3804 MBq)/μA at saturation. There is no serious radionuclidic impurity problem. Production of 99Mo is not viable due to the low cross section (∼130 mb) over the proton energy range of 30 to 50 MeV. The 98Mo(p,γ) 99mTc 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 99mTc with a medical cyclotron is refuted in this study. Countries that do not have access to fission molybdenum-99 for the 99Mo→ 99mTc generator, could consider use of a >17 MeV proton energy cyclotron for regional production of 99mTc.