Background: Using optical techniques for tissue diagnostics (so-called 'optical biopsy') has been a subject of extensive research for many years. Various groups have been exploring different spectral and/or imaging modalities (e.g. diffuse reflectance spectroscopy, autofluorescence, Raman spectroscopy, optical coherence tomography (OCT), polarized light microscopy, etc.) for biomedical applications. In this paper, we report on using multi-wavelength imaging Mueller polarimetry combined with an appropriated image post-processing for the detection of tissue malignancy. Methods: We investigate a possibility of complementary analysis of Mueller matrix images obtained for turbid tissue-like scattering phantoms and excised human normal and cancerous colorectal tissue samples embedded in paraffin. Combined application of correlation, fractal and statistical analysis was employed to assess quantitatively the polarization-inhomogeneous scattered fields observed at the surface of tissue samples. Results: The combined analysis of the polarimetric images of paraffin-embedded tissue blocks has proved to be an efficient tool for the unambiguous detection of tissue malignant transformation. A fractal structure was clearly observed at spatial distributions of depolarization of light scattered in healthy tissues in a visible range of spectrum, while corresponding distributions for cancerous tissues did not show such dependence. We demonstrate that paraffin does not destroy a fractal structure of spatial distribution of depolarization. Thus, the loss of fractality in spatial distributions of depolarization for cancerous tissue is related to the structural changes in the tissue sample induced by cancer itself and, therefore, may serve as a marker of the disease. Conclusion: The obtained results emphasize that a combined use of statistical, correlation and fractal analysis for the Mueller-matrix image post-processing is an effective approach for an assessment of variations of optical properties in turbid tissue-like scattering media and biological tissues, with a high potential to be transferred to clinical practice for screening cancerous tissue samples.

We introduce a Mueller-matrix imaging polarization-based approach for the quantitative digital screening of the polycrystalline structure of fibrillary-based biological tissues in vitro . The morphometric evaluation of histological sections of myocardium was performed utilizing the high-order statistical moments calculated based on the spatial distribution of linear and circular birefringence and dichroism obtained experimentally. We demonstrate that spatial distributions of phase of light and optical anisotropy of scattering inherent to fibrillar networks of myocardium at different necrotic stages can be effectively used as a quantitative marker of stages of myosin fibril degradation. Processing the images of phase of light scattered in biological tissues with high order statistical analysis provides a functional tool for the quantitative characterization of necrotic conditions of the myocardium.

The model of a Mueller matrix description of mechanisms of optical anisotropy typical for polycrystalline films of blood plasma--optical activity, birefringence, as well as linear and circular dichroism--is suggested. On this basis, the algorithms of reconstruction of parameters distribution (polarization plane rotations, phase shifts, coefficients of linear and circular dichroism) of the indicated types of anisotropy were found for different spectrally selective ranges. Within the statistical analysis of such distributions, the objective criteria of differentiation of films of blood plasma taken from healthy women and breast cancer patients were determined. From the point of view of probative medicine, the operational characteristics (sensitivity, specificity and accuracy) of the method of Mueller matrix reconstruction of optical anisotropy parameters were found, and its efficiency in diagnostics of breast cancer was demonstrated.

An optical model for generalized optical anisotropy of polycrystalline networks of albumin and globulin liquor of the human brain has been suggested. The polarization-phase method for spatial and frequency differentiation of linear and circular birefringence coordinate distributions has been analytically substantiated. A set of criteria documenting the dynamics of polarization-phase images of liquor polycrystalline films has been identified in determining time of death.

The optical model of polycrystalline networks of human tissue has been proposed. The values of statistical parameters (statistical moments of the first to fourth order) characterizing the polarization-inhomogeneous images of skin surface in the Fourier domain have been measured. The diagnostic criteria of pathological processes in human skin and the differentiation of its severity degree have been determined.