Quantitative Phase Imaging with Optical Quadrature Microscopy

Presented by William Warger

ABSTRACT
A fusion microscope facility at Northeastern University combines multiple modes of microscopy within a single instrument to produce images of a sample with various contrasts. The uniqueness of the facility comes from the addition of Optical Quadrature Microscopy (OQM) that computes the amplitude and phase of optically transparent samples. The combination of OQM with the other microscopy modes has shown promise for many biological applications. One example is the combination with Differential Interference Contrast (DIC) to implement the phase subtraction cell counting method for counting the number of cells in live mouse embryos. The phase is transformed into an image of optical path, and the DIC image provides distinct cell boundaries for cells within the focal plane when other cells do not lie in the path to the objective. Fitting an ellipse to the boundary of a cell in the DIC image and combining it with the optical path of a single cell creates an ellipsoidal model cell of optical path. Subtracting the model cell from the OQM image will either show the optical path of the culture medium or reveal another cell underneath. Cells are sequentially subtracted until no optical path remains. The non-toxic, phase subtraction cell counting method has produced accurate cell counts in live mouse embryos with cell numbers ranging from 8 - 26. Additional work must be completed to improve the ease of use and processing time, but if verified and applied to human embryos in a clinical setting, this method could revolutionize the clinician's ability to determine embryo viability for IVF procedures.