Verständnis des mikroskopischen Ursprungs der Lichtstreuung in biologischem Gewebe

Abstract

The goal of this work is the understanding of light scattering of biological tissue on the basis of its microscopic structure. The microscopic structure of different phantom medias and tissues is analyzed. The scattering of light at these structures is calculated with different analytic and numeric solutions of the Maxwell equations. These calculations are verified with measurements of the single scattering in this medias. The investigations show that the light scattering in the examined tissues can only be understood with a realistic physical model of the tissue. For various examples, it is possible to derive structural information of the tissue from the measurement of the angle resolved single scattering. By combining the goniometric measurement with the measurement of the collimated transmission, the solutions of the microscopic single scattering are linked to the light propagation in macroscopic volumes of scattering tissues. A solution of the transport theory is applied to calculate the light propagation in a macroscopic volume of a tissue with the measured microstructure. Finally, the measurements of the phase function of biological tissues with nearly the complete direction dependence are presented for the first time. The phase function of structured biologic tissue shows a strong direction dependence from the incident direction and the emergent direction. This verifies our assumption that a solution of the light diffusion in a macroscopic volume of structured tissue can not be approximated with a rotational symmetric phase function like it is commonly done.