3D Printing of SPECT Phantoms using Radioactive Liquid Resin Monomers

Ziel/Aim For multicenter clinical studies, PET/CT and SPECT/CT scanners need to be validated to ensure comparability between diverse scanner types and brands. This validation is usually performed using hollow phantoms filled with radioactive liquids. Recently, 3D printing technology has been introduced for manufacturing of phantoms. However, an approach to directly print radioactive phantoms on a 3D printer does not yet exist. The goal of this work was to develop a method for preparation of radioactive organic liquid resin monomers (“3D printer ink”) and demonstrate successful application of this building material for 3D printing of several test objects.

Methodik/Methods Tc-99m-Pertechnetate solution eluted from a Mo-99/Tc-99m-generator was directly added to the organic liquid resin monomer resulting in a two-phase mixture. A minute amount of trioctylphosphine was included as phase transfer agent. Following mixing, phase separation, and chemical removal of remaining traces of water, the radioactive resin was diluted with the required volume of unlabeled resin and directly used for 3D printing.

Ergebnisse/Results Using our optimized extraction protocol, technetium-99m was efficiently transferred from the aqueous Mo-99/Tc-99m-generator eluate into the organic liquid resin monomer. The observed radioactivity concentration ratio between the organic phase and the water phase was >2000:1. The radioactivity was found to be homogeneously distributed throughout the liquid resin monomer. Radio-TLC and SPECT studies confirmed homogeneous 2D and 3D distribution of radioactivity throughout the printed phantoms. The radionuclides were stably immobilized in the resin, apart from a trace amount of surface-extractable radioactivity under harsh conditions (ethanol at 50°C).

Schlussfolgerungen/Conclusions 3D printing of phantoms incorporating the radionuclide technetium-99m is feasible. When adapting the procedure to long-lived radionuclides, the approach will enable manufacturing of phantoms for scanner validation and quality control.