Nuclear cytoplasmic cell evaluation from 3D optical CT microscope images

The nuclear cytoplasmic ratio (nc-ratio) is one of the measurements made by cytologists in evaluating the state of a single cell and is defined to be the ratio of the size of the nucleus to the size of the cytoplasm. This ratio is often realized in practice by measurements on a single 2D image of a cell image acquired from a conventional microscope, and is determined by the area of the nucleus measured in the 2D image divided by the area of the cytoplasm seen to be outside of the nuclear region. It may also be defined as the ratio of the volume of the nucleus to volume of the cytoplasm, but this is not directly observable in single images from conventional 2-dimensional microscopy. We conducted a study to evaluate the variation of the 2D nc-ratio estimation due to the asymmetric architecture of cells and to compare the 2D estimates with the more precise volumetric nc-ratio estimation from 3D cell images. The measurements were made on 232 3D images of five different cell types. The results indicate that the cell orientation may cause a large amount of variation in the nc-ratio estimation and that nc-ratios computed directly from 3D images, which are independent of cell orientation, may offer a much more precise and useful measurement.