The geometry of an embryo is complex and varies with time. A complete geometric description,
therefore, requires both thickness and shape data for each tissue layer and the fabric and material
properties of each tissue, plus how these characteristics develop with time. The four primary steps involved in the collection of this “spatial-temporal data” are 1. determining embryo shape, 2. defining tissue fabric parameters, 3. determining embryo layer thickness, and 4. measuring material properties.
1. Determining embryo shape
To identify the specific three-dimensional (3D) shape of a live embryo is technically challenging, and our lab has developed an optical method for extracting live embryo 3D geometric information using robotic microscope images taken at several viewing angles (Fig. 5a). By establishing point correspondences among these views and employing suitable reconstruction algorithms [Brodland and Veldhuis 1998, Bootsma, 2005], we can calculate the spatial positions of a collection of surface points. These points can then be meshed and used to obtain a surface representation of the embryo (Fig. 5b). In-plane tissue motions and strain rates are determined using image processing methods that track the motion of groups of cells [Brodland and Veldhuis 1998; Bootsma, 2005].
2. Defining tissue fabric parameters
Tissue fabric parameters are extracted from the time-lapse images using specially designed image processing software. The software detects the boundaries of the cells and uses Fourier analysis to determiner,», and Rvalues. An interpolation scheme is used to map fabric parameters onto the surface mesh.