Mueller matrix description of collimated light transmission through liver, muscle and skin

Propagation of polarized light through liver, muscle and skin was studied using the Mueller Matrix formalism. Collimated HeNe laser light was passed through a set of polarization elements to create one of four possible polarization states (horizontal (H), vertical (V) and 45-degree (P) orientations of linearly polarized light, and right circularly (R) polarized light). The beam passed through thin sections of tissue of varying thickness (0.2-0.9 mm thick). The unscattered, collimated, transmitted light passed through a second set of polarization elements to analyze for transmission of each of the 4 possible polarization states (H,V,P,R). Transmitted intensities for 16 possible combinations of source and detector polarization yielded a data matrix that was converted into a Mueller matrix describing the propagation properties of the tissue. The results were roughly consistent with all three tissue types behaving as ideal retarders whose birefringent values, dn = delta*wavelength/(2*pi*thickness), were in the range of 1x10^-3 to 5x10^-3 which is consistent with the literature. The order of the strength of birefringence was liver <muscle <skin. Although the above birefringence values may apply to muscle, the structured of liver and skin are not necessarily consistent with the ideal retarder model and further work is needed.