Noninvasive monitoring of chick development in ovo using a 7T MRI system from day 12 of incubation through to hatching

Purpose: To determine whether mild cooling of the egg reduces movement to the point where an ultra-high-field (7T) MRI system can be used to noninvasively monitor chick growth in ovo from 12 days incubation through to hatching. Materials and Methods: Group A eggs were incubated at 37.5 degrees C for 21 days. Group B eggs were removed from the incubator on days 12, 15, 17, 18, 19, and 20 of incubation, cooled for one hour, and then returned to the incubator. Group C eggs were cooled as for group B and then individually imaged for 25 minutes using a 7T MRI system before being returned to the incubator. The average size (volume) of the heart, liver, and brain at each stage of incubation was estimated from the T-2-weighted images and compared with existing values in the literature. Results: The combination of cooling and MRI significantly reduced chick movement to allow excellent image acquisition at each stage of incubation. Repeated cooling and/or MRI did not significantly slow down or arrest the development of the chicks in either of the experimental groups. Conclusion: MRI provides a powerful noninvasive tool to study chick development and the growth of individual organs, including the brain, liver, and heart, in ovo from 12 days incubation.