Karyometry: correction algorithm for differences in staining.

OBJECTIVE To describe an algorithm that allows the correction of differences in staining of histopathologic sections while preserving chromatin texture. STUDY DESIGN In order to preserve the texture of the nuclear chromatin in the corrected digital imagery, it is necessary to correct the images pixel for pixel. This is accomplished by mapping each pixel's value onto the cumulative frequency distribution of the data set to which the image belongs, to transfer to the cumulative frequency distribution of the data set serving as standard and to project the intersection down onto the pixel optical density scale for the corrected value. RESULTS Feature values in the corrected imagery, for the majority of features used in karyometry, are between < 1% and a few percent of the feature values in standard imagery. For some higher-order statistical features involving multiple pixels, sensitivity to a shift in the cumulative frequency distribution may exist, and a secondary small correction by a factor may be required. CONCLUSION The correction algorithm allows the elimination of the effects of small staining differences on karyometric analysis.