Comparison between actual and theoretical ellipsoidal shape of human erythrocyte in modulated shear flow

Abstract

BACKGROUND: Current investigation of erythrocyte deformability based on elongation index ignores deviation of erythrocyte shape from the theoretical ellipsoid. Our study investigates how the actual shape of a human erythrocyte deviates from the theoretical ellipsoid shape when subjected to a sinusoidally changing shear flow. We hope to lay the groundwork for developing a more precise theoretical basis for measuring erythrocyte deformability via image analysis. OBJECTIVE: The purpose of this study was to quantify the deviation of erythrocyte shape from the theoretical ellipsoid during dynamic deformation. METHODS: Footage of a single erythrocyte subjected to a quasi-Couette flow was analyzed using MATLAB software. The actual and theoretical shape of erythrocyte were compared using binarization and calculation of its two-dimensional area respectively. RESULTS: The deviation of erythrocyte shape from the theoretical ellipsoid was shown by the percentage difference of actual to theoretical erythrocyte area as a function of its elongation index. The relationship between cell shape and elongation index corresponding to shear conditions was shown. CONCLUSIONS: An erythrocyte subjected to a sinusoidally changing shear flow does not always exhibit an ideal ellipsoid shape but undergoes deviations corresponding to shear conditions. Such deviations should be considered when investigating erythrocyte deformability via image analysis.