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ISAP v.2: SOFTWARE FOR IMAGE SEGMENTATION AND ANALYSIS IN PATHOLOGY

J.J. Berman, G.W. Moore, L.A. Brown.

ISAP, version 2, is an image display and analysis software application developed at the Baltimore Veterans Affairs Medical Center and available at no cost to pathologists, including executable file and source code in Microsoft(R) Visual Basic. Users interactively surround cells of interest using a mouse. In version 2, ISAP permits a choice of methods for smoothing, thresholding, and edge detection. ISAP thresholds the enclosed image, either manually by preselecting a grayvalue threshold or percentage threshold, or automatically according to an algorithm published previously by the authors. ISAP quantitates nuclear features, including measurements of nuclear size (area, summed optical densities, greatest diameter, least diameter); nuclear rim shape (ratio of greatest-to-least diameter, perimeter, contour, fractal dimension); and chromatin texture (standard deviation of optical density, histogram of optical densities). Cytologic measurements are saved in an external database that can be uploaded into commercially available spreadsheet applications for statistical analysis of cell populations. ISAP uses Targa or Windows (.BMP) image formats, and operates on IBM-compatible computers with at least 5 MB hard drive memory, Microsoft(R) Windows v. 3.0 or higher, and 256-color display. To test the robustness of ISAP algorithms, we performed image analysis on 20 normal intermediate cell nuclei at 40x magnification from Papanicolaou-stained cytology smears of the uterine cervix and vagina. Each cell-image was captured as a black-and-white image on a grid of 756 x 486 pixels, with 256 gray-levels per pixel. For each cell, we obtained 10 measurements in focus, and 10 measurements apiece with the stage lowered by 0.1 mmm from the in-focus position, for a total of 400 image-analyses. Area and perimeter were compared by one-way analysis of variance, and were not statistically different in the two focal planes. Results suggest that ISAP is a robust image analysis application, which permits repeatable descriptors for nuclear area and shape in cytologic image analysis.