  Elastic light scattering by mature red blood cells (RBCs) was theoretically
and experimentally analyzed with the discrete dipole approximation (DDA) and
the scanning flow cytometry (SFC), respectively. SFC permits measurement of
angular dependence of light-scattering intensity (indicatrix) of single
particles. A mature RBC is modeled as a biconcave disk in DDA simulations of
light scattering. We have studied the effect of RBC orientation related to the
direction of the incident light upon the indicatrix. Numerical calculations of
indicatrices for several aspect ratios and volumes of RBC have been carried
out. Comparison of the simulated indicatrices and indicatrices measured by SFC
showed good agreement, validating the biconcave disk model for a mature RBC. We
simulated the light-scattering output signals from the SFC with the DDA for
RBCs modeled as a disk-sphere and as an oblate spheroid. The biconcave disk,
the disk-sphere, and the oblate spheroid models have been compared for two
orientations, i.e. face-on and rim-on incidence. Only the oblate spheroid model
for rim-on incidence gives results similar to the rigorous biconcave disk
model.
