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

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