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Quantitative detection and comparison of liver tissues using label-free Mueller matrix microscope

Polarization imaging is a promising technique for probing the microstructures of tissues. Among the available polarimetric techniques, Mueller matrix polarimetry has many distinctive advantages, such as providing label-free and comprehensive descriptions on the properties of biomedical specimens. Recently, for pathological detections we developed a modulus designed Mueller matrix microscope by adding both the polarization states generator (PSG) and analyzer (PSA) to a commercial transmission light microscope. Some preliminary applications on various human cancerous tissues showed that the Mueller matrix microscope can be used to detect the abnormal areas of unstained tissue slices quantitatively. However, whether these parameters are still effective or not for backscattering imaging such as the Mueller matrix endoscope should be analyzed. It is crucial for the future in situ detections using Mueller matrix polarimetry. In this study, we compare these Mueller matrix parameters using the porcine liver tissue samples with appropriate thickness, which can be measured in both transmission and backscattering configurations. The retardancerelated and depolarization-related Mueller matrix imaging parameters between forward and backward imaging results are compared. For a more detailed analysis, we also calculate the indices of polarimetric purity for the depolarizationrelated parameters. The experimental results demonstrate that the retardance-related Mueller matrix parameters have distinct contrasts to characterize the anisotropic and isotropic structures of tissues. However, the contrast mechanisms of the depolarization-related parameters for different tissues still need more studies to confirm.