Automatic segmentation of zona pellucida and its application in cleavage-stage embryo biopsy position selection.

A very important step of Pre-implantation genetic diagnosis (PGD) is embryo biopsy, in which process the zona pellucida (ZP) is cut open partially and a part of cellular material is extracted from the embryo. Recognition of the ZP is necessary not only for embryo biopsy, but also for other applications such as zona pellucida thickness variation (ZPTV), embryo dissection, etc. The ZP opening position is closely related to the cell survival rate after the biopsy. Selection of an unsuitable position may cause blastomere lysis after the ZP opening. Normal procedures of ZP recognition and biopsy position selection involve a skilled human embryologist. In order to make the process automatic, we introduce an automatic segmentation method for ZP recognition by using edge detection and ellipse fitting with a value adjustment algorithm in this paper. An application of ZP recognition in embryo biopsy position selection is also introduced. Our ZP recognition algorithm was able to correctly segment 43 out of 45 sample embryo images, achieving a success rate of 96%. Its application in embryo biopsy position selection achieved a success rate of 93%.