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

Abstract

Purpose: Movement of the chick in ovo severely degrades MR images to the point where its development can not be monitored. We wished to determine if mild cooling of the egg could reduce such motion to the point where an ultra high field (7 Tesla) MRI system could be used to non-invasively monitor chick growth in ovo from 12 days incubation through to hatching. Materials and Methods: Group A eggs were incubated at 37.50C for 21 days; Group B eggs were removed from the incubator on days 12, 15, 17, 18, 19, and 20 of incubation, cooled for 1 hr then returned to the incubator; Group C eggs were cooled as for Group B 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 were estimated from the T2-weighted images and compared to existing values in the literature. Results: The combination of cooling and MR imaging significantly reduced chick movement to allow excellent image acquisition at each stage of incubation. Repeated cooling and MR imaging did not significantly slow down or arrest the development of the chicks in either of the experimental groups. Conclusions: MRI provides a powerful noninvasive tool to study the chick growth and the growth of individual organs including the brain, liver and heart in ovo from 12 days incubation.