A method of non-coherent video-reflectometry based on acquisition and analysis of image sequences in the backreflection mode under white light illumination is examined to characterize the nucleation stage in a plasticized biodegradable polymer (polylactide). Nucleation in the foamed system “polylactide – supercritical/subcritical carbon dioxide” is provoked by a pressure quenching in the quasi-isothermal mode. The features of image formation are discussed for the cases of birth and growth of the surface and bulk pores in the plasticized polymer.
Nucleation in plasticized polymers as the first stage of temperature- or pressure-mediated synthesis of highly porous polymeric matrices is the key factor affecting the structural properties of synthesized matrices. Accordingly, quantification of growth/collapse processes in the ensembles of pore germs during their evolution is of importance for the characterization and control of the morphological and functional properties of matrices. Additionally, analysis of the growth/collapse kinetics for single pore germs allows for evaluation of the physical-chemical properties (the surface tension, the mass fraction of plasticizing agent in the polymer) depending on the external conditions. In this work, the robust image analysis procedures for quantitative description of the pore evolution on the base of video-reflectometry data are discussed. Experimental results obtained in the case of supercritical/subcritical foaming of polylactides are presented.
A new approach to the interpretation of OCT probes of coarse-grained random media is considered. In the framework of the approach, the integrated scan-depth-dependent diffuse reflectivity of a probed sample is estimated using a set of OCT A-scans. A relationship between the integrated reflectivity and a transport mean free path of light propagation in the probed sample is established using Monte-Carlo simulations. The considered technique was applied for characterization of the structure of highly porous polymer (polylactide) matrices synthesized using a supercritical fluidic (SCF) foaming of a pre-plasticized raw polymer. The results of experimental verification of the considered technique are compared with similar data obtained in the framework of other approaches to OCT data interpretation.
We consider the practical realization of a new optical probe method of the random media which is defined as the reference-free path length interferometry with the intensity moments analysis. A peculiarity in the statistics of the spectrally selected fluorescence radiation in laser-pumped dye-doped random medium is discussed. Previously established correlations between the second- and the third-order moments of the intensity fluctuations in the random interference patterns, the coherence function of the probe radiation, and the path difference probability density for the interfering partial waves in the medium are confirmed. The correlations were verified using the statistical analysis of the spectrally selected fluorescence radiation emitted by a laser-pumped dye-doped random medium. Water solution of Rhodamine 6G was applied as the doping fluorescent agent for the ensembles of the densely packed silica grains, which were pumped by the 532 nm radiation of a solid state laser. The spectrum of the mean path length for a random medium was reconstructed.
Random changes in the polarization states of partial contributions to the multiple scattered light fields in a random medium are analyzed using the statistical modeling of polarized light transport in the medium. The mapping of local polarization states on the Poincaré sphere surface clearly indicates the different scenarios of the "order – disorder" transition in the case of Rayleigh and Mie scatterers. If the random medium consisting of small particles is probed by a linearly polarized laser beam, then propagating partial waves keep their linear polarization state but the dispersion of azimuth angles rapidly increases with the increasing average propagation path for these waves. On the contrary, the multiple scattering by random ensembles of the large particles is accompanied by random transformations of the linear polarization of propagating waves to the elliptical polarization. The obtained results are considered in the relation to the known features of polarization decay in the random media.
The problem of cancer control requires design of new approaches for instrumental diagnostics, as the accuracy of cancer detection on the first step of diagnostics in clinics is slightly more than 50%. In this study, we present a method of visualization and diagnostics of skin and lung tumours based on registration and processing of tissues hyperspectral images. In a series of experiments registration of hyperspectral images of skin and lung tissue samples is carried out. Melanoma, basal cell carcinoma, nevi and benign tumours are studied in skin ex vivo and in vivo experiments; adenocarcinomas and squamous cell carcinomas are studied in ex vivo lung experiments. In a series of experiments the typical features of diffuse reflection spectra for pathological and normal tissues were found. Changes in tissues morphology during the tumour growth lead to the changes of blood and pigments concentration, such as melanin in skin. That is why tumours and normal tissues maybe differentiated with information about spectral response in 500-600 nm and 600 – 670 nm areas. Thus, hyperspectral imaging in the visible region may be a useful tool for cancer detection as it helps to estimate spectral properties of tissues and determine malignant regions for precise resection of tumours.
The effect of increase in the uncertainty of local polarization states of laser light forward scattered by random media was studied in the experiments with phantom scatterers. At macroscopic level this effect is related to decay in the degree of polarization of scattered light in the course of transition from single to multiple scattering. Gelatin layers with embedded titania particles were used as the phantom scatterers. Features of distributions of local polarization states in various polarization coordinates were considered.
The aim of the study is combining polarimetry and spectropolarimetry techniques for identifying the changes of opticalgeometrical structure in different kinds of biotissues with solid tumours. It is researched that a linear dichroism appears in biotissues (human esophagus, muscle tissue of rats, human prostate tissue, cervical smear) with cancer diseases, magnitude of which depends on the type of the tissue and on the time of cancer process development.
We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component
and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix
adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix
adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements
transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant
orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were
carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is
insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave
ranges.
The morphological peculiarities of TS mitral valve of the heart of man in normal and abnormal spaced strings of the left ventricle and the study of their structural features depending on the location was studied. There are given the results of comparative statistics, correlation and fractal study population Mueller-matrix images (MMI) of healthy and abnormal (early forms that are not diagnosed by histological methods) BT normal and abnormally located tendon strings left ventricle of the human heart. Abnormalities in the structure of the wings, tendon strings (TS), mastoid muscle (MM) in inconsistencies elements and harmonized operation of all valve complex shown in the features of the polarization manifestations of it laser images.
Different statistical modeling techniques of radiation propagation in epithelial tissue are considered. The two main approaches are: modified classical Monte Carlo method for light propagation in turbid medium and the coherent inverse ray tracing method. Classical Monte Carlo method was modified to take into account polarization of propagated radiation and birefringence which can occur due to tissues commonly found under epithelium. As a supplementary method modified version of classical ray tracing technique is used which takes into account phase of radiation during its propagation in tissue.
An approach to differentiation of the morphological features of normal and pathological human epidermis on the base of statistical analysis of the local polarization states of laser light forward scattered by in-vitro tissue samples is discussed. The eccentricity and the azimuth angle of local polarization ellipses retrieved for various positions of the focused laser beam on the tissue surface, and the coefficient of collimated transmittance are considered as the diagnostic parameters for differentiation. The experimental data obtained with the psoriasis, discoid lupus erythematosus, alopecia, lichen planus, scabies, demodex, and normal skin samples are presented.
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