High-resolution 3D biomechanical mapping of embryos with reverberant optical coherence elastography (Rev-OCE)

The healthy development of embryos depends on several critical biomechanical processes, such as neurulation and the formation of the cardiovascular system. Thus, understanding the structural modifications and changes in stiffness during development is important for understanding the etiology of various congenital diseases, such as anencephaly or spina bifida. In this work, we demonstrate the ability of reverberant optical coherence elastography (Rev-OCE) to map the biomechanical properties of various small animal embryos in high resolution in 3D completely noninvasively and without the need for any exogenous contrast agents. Rev-OCE measurements were performed in both murine and zebrafish embryos to showcase its capability to map the stiffness of commonly used small animal models of disease. The murine embryos were dissected from CD1 mice at gestational day 11, and the zebrafish embryos were isolated at 7 days post fertilization. Rev-OCE imaging was performed using a phase-sensitive optical coherence tomography (PhS-OCT) system, where the samples were placed on a glass window that was attached to a piezoelectric bender. The bender vibrated and generated randomly oriented shear waves in the samples, which were detected by the PhS-OCT system. In addition to holding the samples, the glass window enabled common path imaging for sub-nanometer levels of displacement sensitivity. The results show a clear spatial distribution of stiffness in the embryos. For example, the spinal region of the murine embryos was stiffer than other tissues, and in the zebrafish embryos, the head and swim bladder were stiffer. Embryonic elasticity could provide valuable insight into the critical embryonic developmental process and etiology of various congenital defects.