Patent ID: 8609363

Claim:
A method for counting cells in a cell population to distinguish between live cells and dead cells, said method comprising: (a) treating an aliquot of said population with a vital stain that penetrates dead cells preferentially over live cells; (b) illuminating said aliquot so treated with light of a first wavelength band and forming a first image of said aliquot, wherein light of said first wavelength band is substantially unabsorbed by said vital stain and allows both live and dead cells to be visualized; (c) counting both live and dead cells in said first image; (d) illuminating said aliquot so treated with light of a second wavelength band and forming a second image of said aliquot, wherein light of said second wavelength band is at least partially absorbed by said vital stain; (e) counting, in said second image, live cells that have not been substantially penetrated by said vital stain; and (f) subtracting the number of live cells counted in said second image from the number of live and dead cells counted in said first image to obtain the number of dead cells in said first image, wherein counting cells in the first and second images comprises detecting contrast between the interiors and outlines of cells.