Feasibility of Zirconium-89 Imaging with MERMAID, a small-fish PET scanner prototype

In positron emission tomography (PET), radiolabelling of antibodies with Zirconium-89 ($\mathrm{t}_{1 / 2}=78.4$ hours) has opened the door to studying a variety of diseases, aka. immuno- PET). Due to its low branching ratio for positron emission ${ }^{89} \mathrm{Zr}$ poses some difficulties to PET imaging, e.g. low-count scans. Performance evaluation using phantoms filled with ${ }^{89} \mathrm{Zr}$ is not straightforward due to the Zirconium metallic nature that causes it to stick to the phantoms walls. Here we study the feasibility of ${ }^{89} \mathrm{Zr}$-based PET with MERMAID, a PET prototype dedicated to adult zebrafish and small aquatic animals To this aim, we have developed a 3D printing approach to create solid radioactive phantoms with ${ }^{89} \mathrm{Zr}$. The phantoms were used to study different aspects of MERMAID performance, from energy calibration to image quality. Images were compared to those obtained using ${ }^{18}$ F-FDG 3D-printed solid phantoms. Preliminary results show that MERMAID is capable to image ${ }^{89} \mathrm{Zr}$ but further adjustments are required.