Analysis of light scattering by red blood cells in ektacytometry using global pattern fitting

Ektacytometry measures the shape of red blood cells under shear stress by analyzing the diffraction pattern of laser light passing through a thin layer of suspended cells. Here we model the diffraction pattern using a combination of Bessel and anomalous scattering functions, and employ a global pattern-fitting technique over nine different shear stresses to determine the separate mechanical properties of normal and non-deformable cells. This technique is capable of yielding the correct elongation index of the normal cells over a range of shear stresses even when they are mixed with as much as 50% non-deformable cells. Additionally, the relative concentrations of normal and non-deformable cells can be determined.