A RANDOM WALK MONTE CARLO CODE TO SIMULATE LIGHT SCATTERING IN BIOLOGICAL SUSPENSIONS

D. Chicea1, I.Turcu2

1Faculty of Sciences,  University Lucian Blaga, Dr. Ion Ratiu Str. nr. 7-9, Sibiu, 550012, Romania
2Molecular & Biomolecular Physics Lab., National Institute for Research & Development of Isotopic & Molecular Technologies, P.O.Box 700, 400293, Cluj-Napoca, Romania

In biological suspensions the forward light scattering is done mainly by the contribution of suspended cells. The multiple scattering is almost always unavoidable its contribution being described by Monte Carlo simulations [1,2] or by approximate analytical formula [3]. The Monte Carlo approach we propose, moves one photon at a time and checks all scattering centers to find, at each simulation step, which one will scatter the photon. The single scattering anisotropy was described using the Henyey-Greenstein phase function with the anisotropy parameter g taking values in the range: 0.97 – 0.98. Besides multiple scattering, which is considered intrinsically this approach take into account also the internal reflections on the cuvette walls.
The validation of the simulation results is performed by comparing the obtained angular distribution with the predictions of the effective phase function theory reported recently in the literature [3]. The results show a good agreement in the small concentration range.
Another way to verify the results is to compare the simulation results with the angle resolved experimental measurements performed on human red blood cells (RBC) in suspensions at different haematocrits [4,5]. The obtained results show a good agreement with the experimental data in the range of small angles and small concentrations.
In the literature one find an unreasonable wide range for the RBC scattering cross section and also anisotropy parameter [4] as comparing with the relatively narrow domain for the RBC volume. Work is in progress to perform Monte Carlo simulations with different scattering cross sections, with the confidence that the agreement between simulation and experiment can be extended at higher haematocrits.

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3.	I. Turcu, Effective Phase Function for light scattered by disperse systems – the small angle approximation, Journal of Optics A: Pure and Applied Optics 6 537-543, 2004.
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