3D Printing of Germanium-68 PET Phantoms

We aimed to print a solid-state germanium-68 phantom for positron emission tomography (PET) with precise control of the activity concentration in the phantom material, without cold walls, and with safe handling characteristics. To this end, we developed a novel method for incorporating aqueous germanium-68 into hydrophobic stereo-lithography monomers. With this method, we additively manufactured an 8 mL sphere with near perfect source tightness and homogeneity. A clinical PET scan showed homogenous activity distribution and no fill-related artefacts as seen in a fillable phantom sphere. The energetically favorable process provides complexation and phase transfer of germanium-68 into the hydrophobic building material, ensures homogenous isotope distribution in the rigid polymer matrix and prevents leaching in aqueous environment. Long-lived solid-state phantoms produced with this method will provide consistent and reproducible results in scanner validation, in quality assurance, and in multicenter clinical studies.