Cyclotron production of 99mTc: Experimental measurement of the 100Mo(p,x)99Mo, 99mTc and 99gTc excitation functions from 8 to 18 MeV

Introduction: The cyclotron-based 100Mo(p,2n)99mTc transformation has been proposed as a viable alternative to the reactor based 235U(n,f)99Mo→99mTc strategy for production of 99mTc. Despite efforts to theoretically model the amount of ground-state 99gTc present at end of bombardment for the (p,2n) reaction, experimental validation has yet to be performed. The co-production of 99gTc may have important implications in both the subsequent radiopharmaceutical chemistry and patient dosimetry upon injection. Methods: To determine the extent of 99gTc co-production, we have experimentally measured the 100Mo(p,x)99Mo, 99mTc, and 99gTc excitation functions in the 8-18 MeV range using a combination of natural abundance and 97.42% enriched 100Mo foils along with γ-ray spectrometry and ICP-MS. Although the excitation functions for production of 99Mo and 99mTc have been presented previously in the literature, to the best of our knowledge, this work presents the first experimental evaluation of the 100Mo(p,2n)99gTc excitation function. Results: From the experimental cross-section measurements, the 99mTc production yields and 99mTc/99m+gTc nuclei ratio were calculated for various thick target irradiation conditions. Results suggest that TBq quantities of 99mTc can be achieved with a 99mTc/99m+gTc nuclei ratio that is on par with the current 99Mo/99mTc generator standard eluted at a 24-h frequency. Conclusion: These findings suggest that the cyclotron production of 99mTc may be a feasible alternative to the current reactor-based production strategy.