Insights into Bone Metabolism of Avian Embryos In Ovo Via 3D and 4D 18F-fluoride Positron Emission Tomography

Purpose: The chick embryo is a well-known economical in vivo model system and is widely applied in preclinical research, e.g., bone development studies. It is therefore surprising that no studies concerning the application of F-18-fluoride microPET to bone metabolism have been reported so far. This may be due to motion artifacts or the lack of convenient tracer injection sites. Methods: We resolved the above problems using a combination of sample preparation, anesthesia, microPET imaging, and computational processing, and describe a convenient way of visualizing three- and four- dimensional features of bone metabolism in living chick embryos. Results: The application of F-18-fluoride microPET facilitates repeat measurements, highly reproducible and motion-artifact-free skeletal imaging, and provides quantitative measurements of in ovo metabolic activities in the bones of developing chick. During microPET measurement, radio tracer was injected intravascularly using a custom-made catheter system, allowing us to additionally investigate early time points in tracer kinetics and uptake. Conclusions: Our results show that bone metabolism in living chick embryos can be reproducibly studied and quantified in ovo, even for multiple tracer injections over a longer time period. The use of dynamic F-18-fluoride microPET imaging made it possible to visualize and analyze even small bone structures with excellent quality. Moreover, as our data are comparable to data from corresponding rodent experiments, the use of embryonated chicken eggs is a convenient and economical alternative to other animal models.