Absorption and multiple scattering by suspensions of aligned red blood cells

The analytical theory of multiple scattering [J. Opt. Soc. Am. 60, 1084 (1970)] permits predictions of scattering patterns by homogeneous suspensions of aligned and randomly oriented particles. Predictions for randomly oriented particles have been tested previously. Using an optical system involving a He-Ne laser and suspensions of red blood cells, we tested the theory's predictions for scattering by suspensions in two distinct alignments. The qualitative effects of cell alignment on light scattering are consistent with those predicted, although measured differences in scattering between the two alignments exceed those predicted. We conclude that the theory may provide an optical means of distinguishing particle orientation in multiple scattering suspensions.