Proton induced production and radiochemical isolation of ⁴⁴Ti from scandium metal targets for ⁴⁴Ti/⁴⁴Sc generator development

Scandium-44 g (half-life 3.97 h) shows promise for application in positron emission tomography (PET), due to favorable decay parameters. One of the sources of ^44gSc is the ⁴⁴Ti/^44gSc generator, which can conveniently provide this radioisotope on a daily basis at a diagnostic facility. Titanium-44 (half-life 60.0 a), in turn, can be obtained via proton irradiation of scandium metal targets. A substantial ⁴⁴Ti product batch, however, requires high beam currents, long irradiation times and an elaborate chemical procedure for ⁴⁴Ti isolation and purification. This study describes the production of a combined 175 MBq (4.7 mCi) batch yield of ⁴⁴Ti in week long proton irradiations at the Los Alamos Isotope Production Facility (LANL-IPF) and the Brookhaven Linac Isotope Producer (BNL-BLIP). A two-step ion exchange chromatography based chemical separation method is introduced: first, a coarse separation of ⁴⁴Ti via anion exchange sorption in concentrated HCl results in a ⁴⁴Tc/Sc separation factor of 10²–10³. A second, cation exchange based step in HCl media is then applied for ⁴⁴Ti fine purification from residual Sc mass. In conclusion, this method yields a 90–97% ⁴⁴Ti recovery with an overall Ti/Sc separation factor of ≥10⁶.