Scattering of light waves by biological cells and in tissues

Studies of optical properties of biological cells and tissues have attracted intensive research efforts due to its fundamental importance in a wide range of biomedical optics problems. The aims of this dissertation research are to construct various experimental systems to determine the distribution of refractive index on the cellular scale and the refractive index for turbid and skin samples as well as the theoretical modeling.; A goniometer system with a photoelastic modulation scheme was employed to determine Mueller matrix elements of B-cell and HL-60 cell suspension samples. The angular dependence of the sixteen elements has been determined from the scattered light signals at three wavelengths of 442, 633 and 850 (or 862) nm. A finite-difference-time-domain method and coated sphere model have been used to investigate the effect of intracellular refractive index on the angle-resolved Mueller elements at different wavelengths using the 3D structures of selected B-cells reconstructed from confocal images. With these results, we demonstrated the usefulness of light scattering method in obtaining the cell morphology information.; An automated reflectometry system was constructed and calibrated for accurate measurement of coherent reflectance curves of turbid samples and the presence of coherent and diffuse reflection near the specular reflection angle has been analyzed. The complex refractive indices of turbid samples have been determined based on the nonlinear regression of the coherent reflectance curves by the Fresnel's equations. The complex refractive indices of fresh porcine skin epidermis and dermis tissues, human skin epidermis and dermis tissues and other turbid samples were determined at 8 wavelengths between 325 and 1550nm. Dispersion relations of the real refractive index have been obtained and compared in the same spectral region.