The radionuclides employed in targeted alpha therapy are often actinides (e.g. 225Ac, 227Th) with multiple radioactive daughters. Successful treatment relies on the radiopharmaceutical’s ability to “hold-on” to 225Ac (or 227Th) while it is delivered to the target cancer cell. Imaging surrogates of the radiopharmaceutical permit non-invasive pharmacokinetic assays and enable rapid screening of prospective compounds in living subjects. 134La emits positrons, enabling its use in positron emission tomography (PET) imaging in the form of an in vivo generator with its parent, 134Ce. Due to similar ionic radius and coordination geometries, the 134Ce/134La pair can be used as a surrogate for 225Ac or 227Th (non-PET isotopes) in the investigation of novel alpha-emitting radiotherapeutics.
This talk will focus on using the unique LANL capability at the Isotope Production Facility (IPF) at Los Alamos Neutron Science Center (LANSCE) to develop a production method for 134Ce (t1/2 = 75.9 h, daughter 134La t1/2 = 6.67 m, 2.7MeV β+). In addition, the approach to scale-up for bulk 134Ce production will be discussed. This process involves separation of microscopic (µg) amounts of 134Ce from macroscopic quantities (g) of lanthanum target material. Particular attention is focused on the Ce-La separation development that relies on “in-house” production of a 139Ce tracer (t1/2 = 137.6 d, 165.9 keV γ) via the 141Pr(n,3n)139Pr→139Ce reaction using the secondary neutron flux near a stack of IPF production targets.1
- J.W. Engle, M.R. James, S.G. Mashnik, Ch.T. Kelsey IV, L.E. Wolfsberg, D.A. Reass, M.A. Connors, H.T. Bach, M.E. Fassbender, K.D. John, E.R. Birnbaum, F.M. Nortier, MCNPX characterization of the secondary neutron flux at the Los Alamos Isotope Production Facility, Nuclear Instruments and Methods in Physics Research A 754 (2014) 71.