A method and device are provided for counting cells in a sample of living tissue, such as an
embryo. The method involves obtaining a
microscopic image of the unstained tissue that reveals
cell boundaries, such as a differential interference contrast (DIC) image, and an optical quadrature
microscopy (OQM) image which is used to prepare an image of
optical path length deviation (OPD) across the
cell cluster. The boundaries of individual cells in the
cell cluster are modeled as ellipses and used, together with the maximum
optical path length deviation of a cell, to calculate ellipsoidal model cells that are subtracted from the OPD image. The process is repeated until the OPD image is depleted of phase
signal attributable to cells of the
cell cluster, and the cell count is obtained from the number of cells subtracted. The method is capable of accurately and non-invasively counting the number of cells in a living
embryo at the 2-30 cell stage, and can be employed to assess the
developmental stage and health of human embryos for
fertility treatments.