Reduction of 68Ge activity containing liquid waste from 68Ga PET chemistry in nuclear medicine and radiopharmacy by solidification

PET with68Ga from the TiO2- or SnO2- based68Ge/68Ga generators is of increasing interest for PET imaging in nuclear medicine. In general, radionuclidic purity (68Ge vs.68Ga activity) of the eluate of these generators varies between 0.01 and 0.001%. Liquid waste containing low amounts of68Ge activity is produced by eluting the68Ge/68Ga generators and residues from PET chemistry. Since clearance level of68Ge activity in waste may not exceed 10 Bq/g, as stated by European Directive 96/29/EURATOM, our purpose was to reduce68Ge activity in solution from >10 kBq/g to <10 Bq/g; which implies the solution can be discarded as regular waste. Most efficient method to reduce the68Ge activity is by sorption of TiO2or Fe2O3and subsequent centrifugation. The required 10 Bq per mL level of68Ge activity in waste was reached by Fe2O3logarithmically, whereas with TiO2asymptotically. The procedure with Fe2O3eliminates ≥ 90% of the68Ge activity per treatment. Eventually, to simplify the processing a recirculation system was used to investigate68Ge activity sorption on TiO2, Fe2O3or Zeolite. Zeolite was introduced for its high sorption at low pH, therefore68Ge activity containing waste could directly be used without further interventions.68Ge activity containing liquid waste at different HCl concentrations (0.05-1.0 M HCl), was recirculated at 1 mL/min. With Zeolite in the recirculation system,68Ge activity showed highest sorption