Wide-field Imaging Mueller polarimetry (IMP) is capable to trace the in-plane orientation of brain fiber tracts by detecting the retardance of healthy brain white matter. IMP can help delineating brain tumor during neurosurgery, because tumor cells grow chaotically. However, the underlying crossing fibers may also affect the retardance of healthy brain. We measured with the transmission Mueller microscope two-layered stacks of thin sections of brain corpus callosum tissue. Brain fiber crossing induced the drop in the linear retardance values and azimuth randomization. The depolarization was invariant to mutual orientation of corpus callosum stripes, hence, the studies of brain tumor depolarization may help to distinguish brain tumor from the fiber crossing zones.
SignificanceImaging Mueller polarimetry is capable to trace in-plane orientation of brain fiber tracts by detecting the optical anisotropy of white matter of healthy brain. Brain tumor cells grow chaotically and destroy this anisotropy. Hence, the drop in scalar retardance values and randomization of the azimuth of the optical axis could serve as the optical marker for brain tumor zone delineation.AimThe presence of underlying crossing fibers can also affect the values of scalar retardance and the azimuth of the optical axis. We studied and analyzed the impact of fiber crossing on the polarimetric images of thin histological sections of brain corpus callosum.ApproachWe used the transmission Mueller microscope for imaging of two-layered stacks of thin sections of corpus callosum tissue to mimic the overlapping brain fiber tracts with different fiber orientations. The decomposition of the measured Mueller matrices was performed with differential and Lu–Chipman algorithms and completed by the statistical analysis of the maps of scalar retardance, azimuth of the optical axis, and depolarization.ResultsOur results indicate the sensitivity of Mueller polarimetry to different spatial arrangement of brain fiber tracts as seen in the maps of scalar retardance and azimuth of optical axis of two-layered stacks of corpus callosum sections The depolarization varies slightly (<15 % ) with the orientation of the optical axes in both corpus callosum stripes, but its value increases by 2.5 to 3 times with the stack thickness.ConclusionsThe crossing brain fiber tracts measured in transmission induce the drop in values of scalar retardance and randomization of the azimuth of the optical axis at optical path length of 15 μm. It suggests that the presence of nerve fibers crossing within the depth of few microns will be also detected in polarimetric maps of brain white matter measured in reflection configuration.
Long-term storage and cryopreservation of biological tissues is a global challenge in the fields of regenerative medicine, tissue engineering and implants, because of the formation of large ice crystals that may damage cellular membranes and extracellular matrix (ECM) of collagen. In our studies different thawing mechanisms were tested to achieve more uniform warming of 3D in vitro tissue models, prepared from magnetic nanoparticles (NPs)-modified 3D electrospun nanofiber fleeces and fibroblasts. 3D tissue models frozen in liquid nitrogen were defrosted either with water bath or with radio-frequency (RF) inductive heating of the magnetic NPs and their morphology was compared to that of a non-frozen tissue model using a transmission Mueller microscope and thin sections of all three types of tissue models. Our results demonstrate a sensitivity of the polarimetric parameters obtained with the differential decomposition of Mueller matrices to small changes in sample morphology caused by the different thawing methods. A detailed statistical analysis proved the statistical significance of the experimental data from the three groups of all tissue models.
Diagnosis of degenerative collagen-related skin diseases is a complex process that requires histopathological evaluation of various pathological alterations, which in addition are not unambiguous in themselves. Fluorescence spectroscopy has proven to be valuable tool for tissue differentiation, whereas the biomedical application of tissue polarimetry is establishing as a valuable diagnostic modality. In this work we present the evaluation of experimental results of histology tissue slides from three collagen-related skin diseases: psoriasis, lupus and scleroderma, through fluorescence spectroscopy and Muller polarimetry.
We present a combination of Mueller matrix measurements (635 nm) of cancerous colon specimens and machine-learning approach. Physical realizability filtering and symmetric decomposition were used to extract polarimetric quantities, used as predictors in machine-learning algorithms. The results were visualized using various depolarization spaces. Principal component analysis was used to extract particular features from the model, logistic regression evaluated predictors with high likelihood for tumor detection, while random forest and support vector machines provided the best results for classification. Hence, polarimetry combined with machine-learning approach may increase the histopathology diagnostic accuracy.
Tissue polarimetry could be identified as a complementary optical and non-invasive technique to assist the gold standard histopathology analysis of tissue. In general, polarimetric diagnostics is based on tracing different polarimetric responses (including light depolarization) in tissue zones with structure altered by the benign and pre/cancerous formations. In this manuscript, both healthy and malignant tissue zones of a thick formalin-fixed colon specimen were used for Mueller matrix measurements. Additionally, two more Mueller matrices from Monte Carlo simulation and tissue mimicking phantom were also evaluated, in order to assess polarimetric char- acterization and modeling of turbid media. Symmetric decomposition algorithm of Mueller matrices developed in house was adopted to extract both polarization and depolarization properties, encoded in the Mueller matrix elements. The decomposition products allowed to reveal important information about the internal tissue struc- ture and morphology. The depolarization and polarization parameters were found to follow the particular trends that depend on a choice of parametric space.
We investigated melanin-pigmented skin samples ex vivo, of benign and dysplastic nevi, as well as malignant melanoma, obtained after surgical excision, containing so called safety areas, where a normal skin could be observed, to obtain a complex and complete view about the feasibility of different excitation sources solely and/or in combination to induce fluorescence signal useful for diagnosis of pigmented cutaneous neoplasia. Using the specialized multispectral analysis of the data obtained by fluorescence using excitation in broad spectral range, covering ultraviolet, visible and near-infrared spectral range, contribute considerably to the both the fundamental determination of tumour tissues’ basic spectral parameters, and to increasing the accuracy and specificity in determining the type of pathology when spectral techniques are used that are applicable to the clinical practice. Excitation wavelengths applied namely were 365, 385, 405, 630, 785 nm. As excitation sources were used set of laser and light emitting diodes with output power in the frames of 20-50mW. Microspectrometers USB4000 and QE65000 (Ocean Optics Inc, USA) in the range of 350-1100 nm were used as detectors of the fluorescence spectra obtained using UV-VIS-NIR excitation. These are preliminary investigations based on ex vivo samples, which would be followed by in vivo investigations and comparative studies to obtain the diagnostic accuracy, using optical spectral techniques, which would surpass the existing clinical techniques for early detection and evaluation of skin cancer. The achieved results demonstrate autofluorescence spectra efficiency in highlighting biochemical changes during tumor growth in a broad spectral range.
To explore challenges for further improvement of diagnostic performance, a project aimed at development of technology for tri-modal skin imaging by combining multispectral, fluorescence lifetime and Raman band imaging was initiated. In this study, each of the mentioned imaging modalities has been preliminary tested and updated. Four different multispectral imaging devices were tested on color standards. Picosecond laser-excited fluorescence lifetime imaging equipment was examined on ex-vivo skin samples. Finally, a new Raman spectroscopy setup with 785 nm laser was launched and tested on cell cultures and ex-vivo skin. Advantages and specific features of the tri-modal skin imaging are discussed.
Upon polarimetry the polarization state of light can be obtained for different depolarizing or non-depolarizing medias such as biological specimens. Tissue polarimetry can facilitate a differentiation between healthy and (pre)cancerous tissues, without using any contrast agents and ionizing radiation. Early cancer detection is vital to increase the life expectancy of patients. Turbid medias like biological tissues can change the state and/or decrease the initial polarization of light. Circularly polarized light is preferred as found to possess better ability to detect abnormal changes in tissues, compared to linearly polarized light. In this paper we analyse polarimetric parameters, measured with Thorlabs Stokes meter included in tissue polarimetric experimental set- up in reflection geometry and multiple ex vivo colon samples. The polarimetric device operates in the spectral range between 400 nm and 700 nm, where all experiments had been conducted with wavelength of 635 nm. By reaching reference values for the polarimetric parameters we can propose a theoretical Mueller matrix, that can be used to describe the depolarization properties of the colon samples used in the experiments. The proposed Mueller matrix is to be modelled and experimentally validated to find out if it matches the theory and can be further decomposed to three matrices of depolarization, diattenuation and retardance. All of the aforementioned experimental approaches are a step closer to a pre-clinical trial, which is a bridge to the final and the most challenging goal - tissue polarimetric set-up for in vivo diagnostics.
Apart from the huge physiological importance of hemo-, myo- globin and hemin, they play also an important role as robust and effective recognition agents in chemical and biological sensors. In this aspect the key factor in developing a reliable biosensor is the immobilization on the transducer. Usually immobilization can be produced by chemical methods, but there is frequently a need for homogeneous films of well-controlled thickness or films which can be deposited in a dry environment. The film thickness is of main importance for the optical transducer detected by Surface Plasmon Resonance (SPR) what is used in our study. Hundreds of immobilization protocols have been developed in an effort to ensure high performance sensing. All of them are focused on finding and deposition of appropriate matrices in which the recognition medium can be incorporated. However, the matrix always deteriorates the effectiveness of recognition. It seems that the best approach is to perform direct immobilization of the recognition medium. However, this is not always possible regarding the organic materials – the problem is whether the deposition retains the bioactivity of the recognition agent. On the other hand, the type of the transducer also imposes constrains. For example, the direct immobilization of the proteins is not possible for electrochemical sensors, because of the distance between the redox center and electrodes is too long. Evaluating the pros and cons of organic (protein) film deposition we have considered to study the possibility for direct immobilization of myoglobin, hemoglobin and hemin on SPR transducer. To best of our knowledge, SPR biochip with immobilized myoglobin, hemoglobin and hemin has never been constructed before. We have used spin coating, for direct immobilization and matrix-assisted pulsed-laser evaporation (MAPLE) for elaboration of the SPR biochip. The performance of both SPR chips – direct and MAPLE immobilized, was studied by SPR registration of the binding activity of myo- and hemo- globin ligands with carbon monoxide (CO), carbon dioxide (CO2) and nitride oxide (NO).
The implementation of tissue polarimetry in medicine arises mainly for the need of non-invasive and highly sensitive discrimination between healthy and tumor tissues. This fast, relatively cheap method may be useful for better histological diagnostics by the physicians. Although, the most challenging goal is to apply tissue polarimetric optical system for in vivo measurements, initially one have to optimize the optical system using ex vivo histological samples, phantoms and etc. This paper is focused on the polarimetric parameters from lower gastrointestinal tract histological samples, by using polarized light with several wavelengths, namely 444 nm, 488 nm, 514 nm, 594 nm and 635 nm, detected and processed by commercially available polarimeter. Our experimental results reveal the best wavelength choice in favor of 635 nm for all colon samples used. Light with circular polarization was used in the experiments, as found to survive more scattering events, compared to linearly polarized light. Furthermore, circularly polarized light carries additional information about the phase difference between the two orthogonal components of the electric field (Ex and Ey) and in the case of reflection, the incident state of polarization undergoes a ip of its helicity. By this way, a better detection of histological changes in tissues, related to abnormal tissue structure can be made. Furthermore, the multiwavelength, polarimetric analysis may provide better insight for future in vivo implementation and the results from the ex vivo biological samples presented in this study, contribute to better discrimination based on optical measurements, applicable for tumor detection.
Azopolymers are well known organic materials for polarization holographic recording due to the induced anisotropy under illumination with polarized light. They possess all the desirable characteristics of the known polarization-sensitive materials, as high sensitivity and reversibility, but excel them substantially in the magnitude of the photoinduced birefringence. This makes possible to record reversible polarization gratings with high diffraction efficiency.
In this paper results of experimental investigations on the reversibility properties of birefringence photoinduced in azopolymers are reported, depending on the conditions of subsequent optical and thermal treatment. Thin films of different polymers were prepared in order to examine the kinetics of multiple recording and erasure of birefringence in different types of azopolymers. The reversibility of the polarization recording has been studied using two different method of erasure – by increased temperature and on illumination with circularly polarized light.
Azopolymers are one of the most efficient types of media for recording the polarization state of light. An essential optical parameter to characterize them is the value of the birefringence Δn induced on illumination with polarized light. Laser beam is used as a pump and the birefringence is commonly probed by another laser with wavelength, different from the pump one. However, data about the spectral behavior of Δn are given rarely.
In this work we present experimental data for the dynamics of spectra of birefringence during illumination with pump lasers with wavelengths varying from 355 nm to 514 nm i.e. from the peak of absorbance to the edge of the absorbance band of the azopolymer used. Furthermore, we investigate the influence of nanoparticles from zinc oxide (ZnO) with different concentrations, incorporated in the azopolymer. The azopolymer used for this study is the water soluble poly[1- [4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt], shortly denoted as PAZO. As indicated by our experiments, thin films from this azopolymer can be used for polarization diffractive elements, operating in the entire visible range of the spectrum.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.