Obtaining anisotropy orientation information of turbid media using Mueller matrix derived parameters

Anisotropic structures such as collagen, elastic, and muscle fibers are prevalent in biological tissues. Obtaining the orientation distribution information of these anisotropic structures is important in various biomedical applications. Recently, it is found that polarization imaging, especially Mueller matrix polarimetry can bring abundant microscopic information of complex samples. Previous studies demonstrated that the anisotropic properties in tissues may originate from both scattering or birefringence, which can hardly be distinguished clearly. In this study, we use the Mueller matrix polar decomposition (MMPD) and Mueller matrix transformation (MMT) parameters to obtain the accurate orientations of both the anisotropic scatterers and birefringence of turbid media in backscattering measurement. The experimental results of tissue phantoms and Monte Carlo simulations suggest that the MMT and MMPD parameters have the ability to distinguish the orientations of cylindrical scatterers and birefringence in a complex medium. The preliminary application on bovine tendon tissue samples with and without external force also demonstrates that the Mueller matrix derived parameters can be used to reveal the accurate anisotropy orientations in biological tissues. Moreover, to better understand the relationship between the anisotropy orientations and the Mueller matrix derived parameters, we also analyze the transmission Mueller matrix images of phantoms consisting of wave plates with different axis orientations. The results indicate that the anisotropy orientations information can be clearly revealed using the Mueller matrix derived parameters and may be helpful for future biomedical studies or diagnosis.