Identifying Anisotropic Structures of Non-Stained Melanoma Tissue From Images of Its Mueller Matrix Elements

The Mueller matrix has the capability of providing the complete polarisation information about the response of a medium to the incident polarised light. In this work, we report that the anisotropic structures of non-stained melanoma slices can be identified directly through the Mueller elements. It is observed that the elements M₁₂, M₂₂ and M₂₄ show a high degree of similarity with the three polarisation parameters (the x-y linear diattenuation, the x-y linear depolarization and the ±45° linear birefringence), with PSNR values of 33.4 dB, 35.7 dB and 40.0 dB, respectively. From images of M₁₂, M₂₂ and M₂₄, the cell nuclei and intercellular stroma in the melanoma dermis can be identified with higher contrast. The values of these elements are specific: for the cell nuclei, M₂₂ ranges from -0.75 to -0.27 and M₁₂ ranges from -0.12 to -0.04; for the extracellular matrix, M₂₂, M₁₂ and M₂₄ fall within -0.16 and -0.07, 0.06 and 0.16 and 0.09 and 0.57, respectively. Finally, a theoretical analysis is presented to explain the observations. The results obtained in this is helpful for clinic applications of Mueller matrix images where a method of interpreting measured Mueller matrices rapidly and accurately is essential.