Image Standardization and Determination of Gray Level Threshold in the Assessment of the Myocardial Fibrosis by the Computerized Image Analysis

ABSTRACT

The computerized image analysis is a useful tool for the quantitative assessment of histopathologic findings. In contrast to the usual microscopic examination by pathologists, the computerization should be accompanied with the standardization process of the image. We developed an algorithm to standardize images and to determine the optimal gray level threshold, using a myocardial fibrosis model. Sirius red staining was more convenient for the image analysis than Masson's trichrome staining because of a better contrast with the surrounding structures. To get an optimal measurement, light intensity was standardized at each of the fibrosis, myocardium and background. In this study, the most promising method to determine the degree of fibrosis was that of revising the background without tissue to a gray level of 200, obtaining a green component of the color image, revising the myocardial fiber to 163, and defining a partial ratio as fibrosis index when the gray level threshold was 120. These threshold levels and parameters were determined after drawing the binarization index curves according to the change of the gray level threshold and by the morphological examination of the actual binarization figures overlaid to the original color image. Through these processes we could get a consistent result on the myocardial fibrosis and we expect a similar principle applies when we analyze color images in the histopathologic quantitation by computerized image analysis.