The thermal release of scandium from titanium metal – a simple way to produce pure ⁴⁴Sc for PET application

Abstract

The radionuclide-generator based access to radiopharmaceutical isotopes represents a valuable alternative to directly produced isotopes at particle accelerators or nuclear reactors. The ⁴⁴Ti based generator is of increasing interest for the delivery of PET-radiopharmaceutical isotopes used for imaging. The product of this generator ⁴⁴Sc represents with its 3.97 h half-life and 94.3% positron branching [1] a very promising candidate for labeling PET radiopharmaceuticals. The long half-life of 58.9±0.3 y [2] of the ⁴⁴Ti assures a constant and long lasting production of the daughter nuclide.

Here we present a gas phase separation method of scandium from titanium via thermal release in vacuum. Titanium foils were irradiated with ⁴⁰Ar to produce scandium in multi-nucleon transfer reactions. Another production reaction used was the irradiation of titanium by neutrons from the SINQ neutron source at the Paul Scherrer Institute (PSI).

The titanium metal foils containing ^44mSc and ⁴⁶Sc were heated up for time periods of 15 and 60 min to temperatures between 900 °C and 1500 °C in vacuum. Thus, release properties of scandium from titanium under these conditions were studied. The released scandium was collected on tantalum foils and could be rinsed of with concentrated nitric acid resulting in carrier free scandium nitrate solutions. From the experimental results optimum release conditions are suggested.