Two-point Stokes vector diagnostic approach for characterization of optically anisotropic biological tissues

The purpose of the study is to demonstrate a new method of Stokes-correlometric evaluation of polarization-inhomogeneous images of optically thin (optical thickness smaller than 0.01) histological sections from optically anisotropic biological tissues of different morphological structure. This method is based on a correlation ('two-point') generalization of traditional optical methods for analyzing 'one-point' distributions of polarization states of microscopic images of biological tissues. Analytical algorithms are obtained for describing the 'two-point' complex parameters of the Stokes vector image of a birefringent biological tissue. An experimental technique has been developed for measuring polarization-correlation maps, i.e. the coordinate distributions of the magnitude and phase of the 'two-point' Stokes vector parameters. Within the framework of the statistical and correlation analysis of the obtained data, new quantitative criteria for the differentiation of the optical properties of biological tissues of various morphological structures are found. A comparative analysis of the distribution of the 'single-point' and 'two-point' parameters of the Stokes vector of polarizationally inhomogeneous images was performed. It revealed a higher sensitivity (2-5 times) of the Stokes-correlometry method to variations in orientation-phase structure of biological tissues compared to the single-point approach

3D Mueller-matrix-based azimuthal invariant tomography of polycrystalline structure within benign and malignant soft-tissue tumours

We introduce a method of azimuthally invariant 3D Mueller-matrix (MM) layer-by-layer mapping of the phase and amplitude parameters of anisotropy of the partially depolarizing layers of benign (adenoma) and malignant (carcinoma) prostate tumours. The technique is based on the analysis of spatial variations of Mueller matrix invariant (MMI) of histological sections of benign (adenoma) and malignant (carcinoma) tissue samples. The phase dependence of magnitudes of the first-to-fourth order statistical moments is applied to characterize 3D spatial distributions of MMI of linear and circular birefringence and dichroism of prostate tumours. The high order statistical moments and phase sections of the optimal differentiation of the polycrystalline structure of tissue samples are revealed. The obtained results are compared with the results obtained by conventional methods utilizing polarized light, including 2D and 3D Mueller matrix imaging

Complementary analysis of Mueller-matrix images of optically anisotropic highly scattering biological tissues

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

Polarimetric and spectral imaging approaches for quantitative characterization of inhomogeneous scattering media including biotissues

Abstract In this thesis, light-tissue interaction was investigated through different experimental and analytical methodologies to analyze optical and polarization properties over time and the obtained results were utilized in biomedical and food science applications. In this thesis, soft biological tissues (pork samples) were selected as a biological tissue due to their similarity to human tissue. First, the relative spectral changes of absorbance were studied by applying two different custom-built configurations. A Monte Carlo modelling and principal component analysis (PCA) method were applied further to the absorbance dataset to provide thorough studies for a spectroscopic approach. Second, a novel application of Mueller matrix (MM) imaging polarimetry was pioneered to visualize the dynamics of the tissue polarization properties over time with a custom-built Mueller matrix imaging polarimeter (MMIP). Frequency distribution histograms (FDHs) and the changes in the statistical moments of the MM elements were analyzed over time to provide qualitative and quantitative information of the tissue polarization properties. Finally, a new Stokes-polarimetry was introduced to examine optically thin histological sections from optically anisotropic biological tissues with different morphological structures. In summary, in spectroscopic and imaging polarimetry approaches, prominent changes in optical properties of the examined soft biological tissues were discriminated over time. The obtained results are promising in the development of a novel non-destructive tool for monitoring biological tissues for application in biomedical applications and the food industry. The Stokes-polarimetry method can provide a comparative analysis of different polarimetric techniques and prove the diagnostic potential of Stokes correlometry of pathological changes in the orientation-phase structure of biological tissues.Tiivistelmä Tässä opinnäytetyössä valon ja kudoksen vuorovaikutusta tutkittiin erilaisilla kokeellisilla ja analyyttisillä menetelmillä, jotta voitiin tunnistaa optisten ja polarisaatio-ominaisuuksien alkuvaiheita ja hyödyntää saatuja tuloksia biolääketieteellisissä ja elintarviketieteellisissä sovelluksissa. Tässä työssä pehmeäksi biologiseksi kudokseksi valittiin sianlihanäytteet niiden ja ihmiskudoksen samankaltaisuuden vuoksi. Ensiksi pehmeiden biologisten kudosten absorbanssin suhteellisia spektrimuutoksia tutkittiin soveltamalla kahta erilaista räätälöityä kokoonpanoa, jotka yhdistettiin. Monte Carlon mallintamista ja pääkomponenttianalyysimenetelmää (PCA) sovellettiin edelleen absorbanssiaineistoon, jota voitiin perusteellisesti tutkia spektroskooppisesti. Toiseksi Mueller-matriisin (MM) kuvantamispolarimetrian uudella sovelluksella pyrittiin visualisoimaan kudosten polarisaatio-ominaisuuksien dynamiikkaa ajan suhteen räätälöidyllä Mueller-matriisikuvauspolarimetrillä (MMIP). Taajuusjakauman histogrammit (FDH) ja MM-elementtien tilastolliset momenttimuutokset analysoitiin ajan suhteen, jotta saataisiin kvalitatiivista ja kvantitatiivista tietoa kudosten polarisaatio-ominaisuuksista. Lopuksi otettiin käyttöön uusi Stokesin polarimetrinen menetelmä, jotta voitiin tutkia optisesti ohuita histologisia leikkauksia anisotrooppisista biologisista kudoksista, joilla on erilainen morfologinen rakenne. Yhteenvetona voidaan todeta, että spektroskooppisesti ja kuvantamispolarimetrillä tutkittujen pehmeiden biologisten kudosten optisten ominaisuuksien huomattavat muutokset erotettiin selvästi ajan suhteen. Saadut tulokset ovat lupaavia, kun kehitetään uutta ainetta rikkomatonta työkalua biologisten kudosten seurantaan biolääketieteellisissä sovelluksissa ja elintarviketeollisuudessa. Stokesin polarimetrisella menetelmällä voidaan tuottaa vertaileva analyysi erilaisista polarimetrisistä tekniikoista ja todistaa Stokesin korrelometrian diagnostinen potentiaali biologisten kudosten orientaatiovaiheen rakenteessa

Evolution of raw meat polarization‐based properties by means of Mueller matrix imaging

The possibilities of using Mueller matrix (MM) imaging polarimetry to assess meat quality have not yet been sufficiently explored. In the current study, the fresh porcine muscles are imaged at room temperature with a wide‐field MM imaging polarimeter over 26 hours to visualize dynamics of tissue optical properties through applying Lu‐Chipman decomposition. The frequency distribution histograms (FDHs) and statistical analysis of the MM elements show prominent changes over time. The wavelength spectra of both total depolarization and scalar retardance have dips at 550 nm whereas their values continuously increase with time; the former is referred to the increase of number of scattering events and decrease of myoglobin absorption in the red part of visible spectra related to meat color and freshness, while the latter is associated with the increase in birefringence and meat tenderness. The obtained results are promising to develop a novel fast non‐contact optical technique for monitoring of meat quality