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

PET with (68)Ga from the TiO(2)- or SnO(2)- based (68)Ge/(68)Ga generators is of increasing interest for PET imaging in nuclear medicine. In general, radionuclidic purity ((68)Ge vs. (68)Ga activity) of the eluate of these generators varies between 0.01 and 0.001%. Liquid waste containing low amounts of (68)Ge activity is produced by eluting the (68)Ge/(68)Ga generators and residues from PET chemistry. Since clearance level of (68)Ge activity in waste may not exceed 10 Bq/g, as stated by European Directive 96/29/EURATOM, our purpose was to reduce (68)Ge 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 the (68)Ge activity is by sorption of TiO(2) or Fe(2)O(3) and subsequent centrifugation. The required 10 Bq per mL level of (68)Ge activity in waste was reached by Fe(2)O(3) logarithmically, whereas with TiO(2) asymptotically. The procedure with Fe(2)O(3) eliminates ≥90% of the (68)Ge activity per treatment. Eventually, to simplify the processing a recirculation system was used to investigate (68)Ge activity sorption on TiO(2), Fe(2)O(3) or Zeolite. Zeolite was introduced for its high sorption at low pH, therefore (68)Ge activity containing waste could directly be used without further interventions. (68)Ge 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, (68)Ge activity showed highest sorption.