A 3-D code for solving the set of Maxwell equations with the finite-difference time-domain method is developed for simulating the propagation and scattering of light in biological cells under realistic conditions. The numerical techniques employed in this code include the Yee algorithm, absorbing boundary conditions, the total field/scattered field formulation, the discrete Fourier transformation, and the near-to-far field transform using the equivalent electric and magnetic currents. The code is capable of simulating light scattering from any real cells with complex internal structure at all angles, including backward scattering. The features of the scattered light patterns in different situations are studied in detail with the objective of optimizing the performance of cell diagnostics employing cytometry. A strategy for determining the optimal angle for measuring side scattered light is suggested. It is shown that cells with slight differences in their intrastructure can be distinguished with two-parameter cytometry by measuring the side scattered light at optimal angles.
We present a new interference pattern based scheme for the cell diagnostics. In this approach the biological cell is illuminated by a spherical light source. The interference pattern that is created by the unscattered incident light and the light that is scattered by a cell is used for cell diagnostics. A three-dimensional computational code (AETHER) for solving the full set of Maxwell’s equations with the Finite-Difference Time-Domain (FDTD) method has been used to numerically determine the interference light intensity pattern between the unscattered incident light and the scattered light. Features of the interference patterns that are obtained for different cellular parameters and structures are discussed. We have numerically shown that the interference intensity pattern can replace the purely scattered light patterns currently used in cell diagnostics.