Gallium radioactive labelling using radionuclide generators from different suppliers

Introduction
The increase in demand for ⁶⁸Ga PET scans coupled with cost issues brought up by the purchase of radionuclide generators and kits, lead us to enhance the gallium labelling output. To do so, it is common practice to pool eluates from two identical radionuclide generators. A higher amount of gallium chloride is then available for the labeling process thus allow to treat a greater number of patients.
Because of our high-energy hot cell configuration, we are compelled to use two different trademark radionuclide generators. The aim of this work is to present our method and retrospectively assess its results in regard of the labelling conducted.

Method
The radionuclide generators used are GalliaPharm (^®GP, from ECKERT & ZIEGLER) and Galliad^® (GA, from IRE-EliT).
GP®‘s elution requires the following medical devices (MD): 0.22µm filter, acid-resistant needle, 2-piece 20mL syringe, female to female luer lock connector.
GA^®‘s elution requires: specific tubing, acid-proof needle, 2-piece 2mL syringe, TC-ELU 15^® (elution vials under partial vacuum and nitrogen atmosphere).
Radiochemical purity was assessed through thin-layer chromatography in accordance with the kit’s summary of product characteristics (SmPC).

Results
Elution’s process is standardized for the labelling of both SOMAKIT^® and LOCAMETZ^®’s kits. Both radionuclide generators elution is performed concomitantly. The kit vial is used as a reaction vessel.
GP^® is eluted directly into the vial kit by pushing 5mL of hydrochloric acid using an syringe pump. Eluate passes through a 0.22µm filter connected to an acidic-resistant needle set into the kit.
GA^® is eluted into the TC-ELU 15® vial. Eluate is then transferred into the vial kit using a 2-piece (2mL) syringe and an acid-proof needle.
Immediately after, the vial is gently swirled for up to ten seconds to promote good complexation between gallium chloride and drug carrier. Following steps are done in accordance with each kit’s SmPC.
Resulting volume is respectively of 10.3mL (SOMAKIT) ^®and 10.7mL (LOCAMETZ^®).
The radiochemical purities obtained through our process are in accordance with each kit’s SmPC.

Conclusion
Pooling eluates from different references of 68Ga radionuclide generators into one radiolabeling process is unseen.
Besides enabling to have a higher volumetric activity and an increase in the number of patients per kit, this work proves that it is possible to extend the pooling of eluates to generators of different technologies while complying with the required radiochemical purity specifications.
Such a method would prove itself to be useful in front of shortages and uncertainties of contract biddings.

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