Speaker
Description
225Ac and 212Pb are at the core of over 3 dozen current pre-clinical and clinical studies as of January 2024 that have the potential of addressing upwards of 1.3 million cancer patients in the US alone. Radiochemically-pure 225Ac can be extracted from 229Th (7880 y), which is itself a decay product of 233U (159,000 y) while 212Pb can be obtained from 228Th (1.91 y) produced via double neutron capture on 226 Ra using the High-Flux Reactor at Oak Ridge National Laboratory [1] or via ton-scale separation of 228Ra (5.75 y) from natural 232Th [2]. However, these decay-based production routes can produce only a small fraction of the anticipated demand due to the long-lives of the decay precursors and the availability of suitable high-flux reactors, limiting the scalability needed to facilitate large-scale radiopharmaceutical production. 225Ac accelerator production methods also have significant challenges. High-energy proton bombardment of 232Th targets produces significant 227Ac contamination and the use of energetic proton or photon beams on 226Ra targets result in limited production rates and dangerous levels of target heating from electromagnetic interactions in the radium target. A production pathway for these essential radionuclides is needed that doesn’t result in heating of the radium target.
The answer involves the use of fast neutrons. Energetic neutrons can produce both the 225Ra and 224Ra precursors for 225Ac and 212Pb via the (n,2n) and (n,3n) reaction respectively. Since neutrons carry no charge, they do not meaningfully heat the radium target, and their long range allows for easy production scalability using larger radium targets. In this talk I’ll review all the 225Ac and 212Pb production mechanisms and show the result of two experiments at the LBNL 88-Inch cyclotron that clearly demonstrated simultaneous production of both radioisotopes using fast neutrons from thick target deuteron breakup [3].
[1] "An Experimental Generator for Production of High-Purity 212Pb for Use in Radiopharmaceuticals", Ruth Gong Li, Vilde Yuli Stenberg and Roy Hartvig Larsen. Journal of Nuclear Medicine January 2023, 64 (1) 173-176; DOI: https://doi.org/10.2967/jnumed.122.264009
[2] https://www.thormedical.com/
[3] "Secondary Neutron Production from Thick Target Deuteron Breakup. JT Morrell, AS Voyles, JC Batchelder, JA Brown and LA Bernstein. Phys. Rev. C 108, 024616 (2023). DOI: https://doi.org/10.1103/PhysRevC.108.024616
| Contribution category | Experiment |
|---|---|
| Presenter status | Faculty/Staff |