Copper-67

Copper-67 decays purely by beta-minus emission with a physical half-life of 61.8-62 hours (about 2.58 days) to stable zinc-67, with a mean beta energy of about 141 keV (maximum energies at 377, 468 and 562 keV) and useful imaging gammas at 93 keV and 184.6 keV (about 49% abundance), which support SPECT-based dosimetry.

Its principal theranostic appeal is chemical identity with copper-64, the positron-emitting isotope used for PET imaging of the same chelator-conjugated agent (e.g. SAR-bisPSMA, SARTATE): the same molecule with the same biodistribution can be imaged pre-therapy with 64Cu and then dosed with 67Cu, avoiding the surrogate mismatch inherent in most other theranostic pairs.

Production historically used reactor or lower-energy cyclotron reactions (67Zn(n,p)67Cu, 68Zn(p,2p)67Cu, 70Zn(p,α)67Cu), each limited to modest specific activity. A step change came from high-energy bremsstrahlung photonuclear production, 68Zn(γ,p)67Cu, using electron linear accelerators to irradiate enriched 68Zn targets; the US Department of Energy Isotope Program's Low Energy Accelerator Facility (LEAF) uses this route to supply no-carrier-added 67Cu at specific activities above 1850 GBq/mg. Clarity Pharmaceuticals and the DOE Isotope Program are among the groups scaling supply; 67Cu is not dependent on nuclear reactor neutron flux, so it avoids the reactor-capacity bottleneck that constrains 177Lu and 225Ac.