VOLUME AND SURFACE-AREA MEASUREMENT OF VIABLE CHONDROCYTES IN-SITU USING GEOMETRIC MODELING OF SERIAL CONFOCAL SECTIONS

This study describes a technique for noninvasive determination of the surface area and volume of chondrocytes using the confocal scanning la ser microscope, and the fundamental limitations associated with its ap plication. Using geometric modelling principles, an isointensity surfa ce contour was formed from a series of optical sections recorded with the confocal microscope. Using a combined surface- and volume-based al gorithm, the surface area, volume and other morphometric descriptions were calculated from a polygonal description of the cell surface. The high image contrast required for repeatable identification of the cell border was achieved through the use of a fluorescent dye, which was e xcluded from cells by an intact membrane. Calibration results indicate d that the theoretical modelling algorithm is relatively precise when applied to simulated convex (ellipsoidal) cells, with overall errors o f less than 0.5% in surface area and volume measurements. When applied to low-noise, high-contrast volume data recorded on the confocal micr oscope, typical coefficients of variation of 2-4% were determined for length measurements, 2-5% for volume measurements and 3-6% for surface area measurements either for latex microspheres or for chondrocytes. While the precision of the method is comparable to standard histologic al techniques, its accuracy is difficult to assess, as systematic erro rs are unpredictable and may be introduced from several sources.