Modeling Human Embryos Using a Variational Level Set Approach

At fertility clinics, living human embryos are evaluated by visual inspection of light microscopy images. The criteria to assess the quality are number of blastomeres (cells) of the embryo, regularity of size and degree of fragmentation. Today, this evaluation process is based on interpretation of 3D information projected to 2D images. It is believed that an overall improvement in the process could be achieved, if the process could be based on 3D information with quantitative measurements instead. Unfortunately, due to limitations in the acquisition process, the 3D information cannot be obtained directly. Previous work on building 3D models has used solid spheres to simulate the position and size of the blastomeres. This thesis’ main objective is to make use of the level set methodology to address this problem. A new 3D model is developed by using a variational level set approach to model the blastomeres and the interior of the Zona Pellucida as elastic objects with individual surface tensions, thereby enabling them to deform due to mutual object interaction. Positional information from microscopy images is embedded as soft constraints requiring that an obtained curve must be located on an object’s surface and that the object must be located inside a bounding generalized cylinder passing through this curve. There is no quantitative standard to measure the results against, but results are promising and correspond well to human interpretation of the light microscopy images.