In ovo model with emu eggs as novel alternative to animal testing in preclinical imaging research.

Background: Large-size in ovo models are receiving increasing attention since they comply with the 3R requirements (Replacement, Reduction and Refinement) by limiting the number of fully developed laboratory animals. In preclinical imaging research, a specific advantage is that they do not require dedicated scanners for small animals (expensive and rarely available) but are suitable for imaging studies by scanners used for clinical examinations. The present study evaluated large-sized fertilized emu eggs as a candidate model for preclinical imaging research in nuclear medicine by [¹⁸F]FDG-PET/CT, aiming to increase the repertoire of alternative models to conventional animal testing.

Results: Of 31 fertilized eggs, 18 eggs had viable peripheral vasculature available for vessel detection via MRI or CT. Both modalities provided reliable information on location and dimension of target blood vessels. Optimization of catheterization proved challenging, and only 5 [¹⁸F]FDG-PET/CT scans were entirely successful in demonstrating the expected biodistribution pattern. In vivo and ex vivo organ activity showed a statistically significant correlation (Spearman's Rho: 0.9091; p = 0.00004).

Conclusion: The emu egg model is suitable for preclinical imaging research with clinical scanners. Considering the shorter seasonal availability but longer incubation period of fertilized emu eggs, this model is a valid complement to the recently introduced ostrich egg model, available only in warm periods. In combination, these models offer a year-round flexibility for in ovo imaging research.