Ultra-High-Field MR Microscopy of the Upper Extremity of the Chicken in Vivo Throughout the in Ovo Period

Introduction: Ultra-high-field magnetic resonance imaging (UHF-MRI) with an in-plane spatial resolution < 100 μm is known as magnetic resonance microscopy (MRM). This technique provides high-resolution noninvasive anatomical images and allows longitudinal assessment of embryonic avian development. The aim of the present study was to evaluate the feasibility of in vivo anatomical MRI assessment of the developing upper extremity of the chicken in ovo.

Material and Methods: Thirty-eight fertilized chicken eggs were examined at 7 T (ClinScan, Bruker BioSpin, Germany) acquiring high-resolution T2-weighted anatomical images with an in-plane resolution of 78 × 78 µm. To reduce motion artifacts, the eggs were moderately cooled before and during MR imaging. Two eggs were imaged daily for the entire developmental period, and 36 eggs were examined pairwise at only one time point during the embryonic period. Development of the upper extremity was assessed anatomically and quantitatively. Chondrification on MRI was correlated with histologic examination.

Results: MRM allowed identification from embryonic stage D5 onward. First chondrification of the upper extremity was visible at stage D7, and differentiation of the forearm was possible from stage D9 with excellent correlation to histology. Repeated cooling and MRM had no influence on the development of the chicken.

Conclusions: MRM allows in vivo assessment of embryonic development of the upper extremity of the chicken in ovo without affecting normal development. The method provides noninvasive anatomical information supplemented by quantitative evaluation. With increasing availability of UHF-MR systems, this technique may provide a noninvasive complementary tool in experimental musculoskeletal radiology.