Interference effects caused due to the coherent waves traveling in time reversed paths produces an enhanced backscattering (EBS) cone, which is known to be inversely proportional to the transport mean free path length (l_s^*) of a scattering media. In biological media, l_s^* (0.5-2mm) >> wavelength λ, results in an extremely small (~0.001⁰) angular width of the EBS cone making the experimental observation of such narrow peaks to be difficult. Hence, we developed a low coherence enhanced backscattering (LEBS) technique by combining the EBS measurements with low spatial coherence illumination and low temporal coherence detection. Low spatial coherence behaves as a spatial filter preventing longer path lengths and collects photons undergoing low orders of scattering. The experimental angular width of these LEBS peaks (~0.3⁰) are more than 100 times the width of the peak predicted by conventional diffusion theory. Here we present a photon random walk model of LEBS cones obtained using Monte Carlo simulation to further our understanding on the unprecedented broadening of the LEBS peaks. In general, the exit angles of the scattered photons are not considered while modeling the time reversed interference phenomenon in diffusion regime. We show that these photon exit angles are sensitive to the low orders of scattering, which plays a significant role in modeling LEBS peaks when the spatial coherence length of the light source is much smaller than l_s^*. Our results show that the model is in good agreement with experimental data obtained at different low spatial coherence illumination.

Recently we discovered that in developed integrated flow cytometry using combination high resolution transmission and two beam (pump-probe) of photothermal microscopy with flow module the temporal fluctuation of probe beam even without pump laser pulse are very sensitive to functional states of single cells (e.g. with 2-3 differences in average fluctuation amplitude for live and dead cells). In this paper we are focusing on theoretical and experimental studies of these new phenomena using thermolens schematics with highly stabilized continuous-wave He-Ne laser and photodiode/photomultiplier with pinhole. This scheme allows to study both random and laser-induced thermolens effects in passive and active mode including short and long term monitoring of scattered light fluctuation in trans-illumination mode at single cellular and even sub-cellular levels in vitro, and in vivo. We demonstrate these schematics has some potential to monitor intracellular dynamics including change in cell metabolism, and necrosis, especially, under pump laser impacts in vitro in stationary condition. Besides, we present some relevant data obtained with other similar schematics, including evaluation of bacterial motility by dynamic light scattering. We discuss further potential developing this approach for flow cytometry with fast speed photodetector and digital camera and the multi- wavelength statistical and correlation analysis of speckle-related signals in applications to analysis of complex motions and functional properties of cells in bioflows including the evaluation of the rotational and translational components of the motion of individual live and dead cells.

A three-phase shifting method is introduced to spectral OCT to eliminate mirror image and autocorrelation noise inherent in spectral OCT signal, thus improves the measurable range of spectral OCT by a factor of 2. The feasibility of such method is demonstrated using a mirror like object. Comparison between two-phase and three-phase shifting methods is performed using a 1mm slab as the object. An intact porcine cornea tissue in vitro is also used to show the potential of this method for biological imaging.

The speckle contrast ratio in optical coherence tomography images has been shown to depend on scatterer density when the detected signal is dominated by single backscattering. Here we investigate the influence of multiple scattering on the speckle contrast ratio, and also on the parallel and perpendicular polarization channels in polarization-sensitive optical coherence tomography images, including the correlation between them. Conditions under which the contrast ratio and polarization sensitive detection can be used to discriminate regions of OCT images affected by multiple scattering are discussed. The contrast ratio and the correlation between polarization channels were both found to markedly decrease as the ratio of multiple to single scattering increased. A high correlation between polarization channels, indicating that imaging is being performed in the single-scattering regime, provides greater confidence in interpreting the value of scatterer density obtained from the contrast ratio.

It is known that glucose interacts with plasma proteins and hemoglobin in erythrocytes. Glycated (glycosylated) hemoglobin is the result of an irreversible non-enzymatic fixation of glucose on the beta chain of hemoglobin A. The amount of glycated hemoglobin depends on blood glucose concentration and reflects the mean glycemia of about the previous 2-3 months. Glycated hemoglobin is a useful marker for long-term glucose control in diabetic patients. Therefore, the search of quick and high sensitive methods for measurement of glycated hemoglobin portion in blood is important. This study is focused on the determination of refractive index of hemoglobin solution at different glucose concentrations. Measurements were performed using Abbe refractometer at 589 nm and optical coherence tomography (OCT) at 820 nm. The different amount of glucose (from 0 to 1000 mg/dl with a step 100 mg/dl) was added to hemoglobin solution. Theoretical values of refractive index of hemoglobin solutions with glucose were calculated supposing non-interacting hemoglobin and glucose molecules. There is a difference between measured and calculated values of refractive index. This difference is due to glucose binding to hemoglobin. It is shown that the refractive index measurements can be applied for the evaluation of glycated hemoglobin amount.

Monte-Carlo simulations are applied to study the polarized light transport from a localized light source in layered multiple scattering media with the expressed macroscopic anisotropy of optical properties. The shape and orientation of the equal intensity profiles for various polarization states of backscattered light are analyzed in the dependence on the distance between the source and detection point. Obtained results are compared with the experimental results obtained by other authors in the experiments with tissue phantoms and in-vivo tissues. Various numerical techniques for reconstruction of the optical parameters of multiple scattering anisotropic media on the basis of polarization analysis of backscattered light are considered. The developed technique can be used as the theoretical basis for morphological diagnostics of anisotropic tissue layers consisting of collagen fibrils (such as, e.g., derma) by means of polarization videoreflectometry.

The potential for monitoring of the laser-mediated thermal modification of tissue by means dynamic laser speckles methods is examined. The specific case of delivering of speckle-modulated light backscattered by cartilage with the use of a fiber-optic bundle probe is considered. The proposed technique is experimentally compared with the conventional laser speckle contrast analysis. Both techniques similarly display the basic features of laser-mediated alterations in tissue but the bundle-based technique provides the monitoring of tissue modification with more details and more pronounced correlation between the speckle contrast and the tissue temperature. The possibility of evaluation of the fundamental physical-chemical parameters of tissue modification (in particular, the activation energy) from the temperature-dependent dynamics of the speckle contrast is demonstrated.

Influence of laser irradiation and low-coherent speckles on the colonies grows of Pseudomonas Aeruginosa is studied. It has been demonstrated that effects of light on the inhibition or re-activation of cells are connected with speckle dynamics. The regimes of cell suspension perfusion with purpose of devitalization of bacteria are found on the base of experimental investigations. Mathematical model of interaction of low-coherent laser radiation with bacteria suspension has been developed. Parameters of mathematical model have been identified. Computer simulations of the processes of laser-cells interaction have been carried out.

We propose a new image reconstruction algorithm for functional near infrared spectroscopic imaging of the brain. Our approach considers the functional changes in the optical properties to be support limited. We simultaneously estimate the values of changes as well as the support from the available measurements. Since this scheme exploits the structure inherent to functional imaging, it provides reconstructions with better spatial resolution and is more robust to noise.

A series of images are acquired by optical intrinsic signal imaging (OISI) at 550 nm during cortical spreading depression (CSD) in rats. Temporal clustering analysis (TCA), which is an exploratory data-driven technique that has been proposed for the analysis of fMRI data and laser speckle contrast images, is applied to tract the extreme response during CSD. The minimum of optical intrinsic signals (OIS) during CSD in each pixel, corresponding to the maximum change of regional cerebral blood volume (CBV), is determined by TCA. Interestingly, the spatial pattern of the maximum activation shows the ongoing expanding circle. In order to describe the circular pattern quantitatively, we present the least square estimation (LSE) to detect the three parameters of the expanding circles (radius R, center coordinates (a, b)) at each time point (i.e. in each frame). The evaluated mean centers of the circles (1.50±0.06 mm, 2.62±0.03 mm) were tightly correlated with the pinprick site (1.4±0.2 mm, 2.5±0.2 mm). According to the varying values of the radiuses at different time point, we calculate the propagated speed of the CSD at 3.96 mm/min. The results substantiate the CSD spreads like a wave from the induced site to the periphery at 2~5 mm/min over the cortex. So, the combination of TCA and LSE enables the image analysis of OISI more automatic and effective.

In intrinsic signal optical imaging data, the response signal related cortical activity is very small compared to the background signal intensity and accompanied with unwanted noise from several different sources. Although there are some sophisticated data analysis techniques developed to achieve this critical demand, experience proved that no method perfect enough to be optimal for all experimental situations. Here we introduced a simple and practicable pre-processing method to attenuate the global noise source, such as the fluctuation of the illuminating light, changes of the animal's blood pressure and vasomotor oscillations. Before image processing to characterize the spatiotemporal response from cortical activity, each frame of image data was divided by the average or median of the current frame data. We applied the method to both simulated data and experimental optical imaging data to evaluate the validity and limitation.

Many mammalian neuronal networks, such as Central Nervous System (CNS), fire single spikes and complex spike burst. In fact, the conditions for triggering burst are not well understood. In the paper multi-electrode array (MEA) is used to record the spontaneous electrophysiology activity of cultured rat hippocampal neuronal networks for long-term. The transition from single spikes to burst is observed on networks that is cultured about 3 weeks and quickly fire before burst activity. The firing rate during burst is lower than that before burst, but the difference of inter spike intervals (ISIs) between the two firing patterns is not distinctness. Moreover, the electrical activities on neighboring electrodes show strong synchrony during burst activity. In a word, the generation of burst requires that network has a sufficient level of excitation as well as the balance by synaptic inhibition.

Learning a new behavioral task is an exploration process that involves the formation and modulation of sets of associations between stimuli and network's responses. The dissociated rat hippocampal neurons were cultured on a multi-electrode array (MEA) substrate. So the electrophysiological activity can be extracellularly recorded, the response of network dynamics induced by electrical pulse stimulation can be analyzed using the recorded data. The test stimuli patterns were different interval twice stimuli. Each stimulus is voltage-controlled pulses (100μs at +0.6V, followed by 100μs at -0.6V). With the intervals between two stimuli decreasing such as a series of 100ms, 50ms, 20ms and 10ms, the response duration of cultured neuronal network increased. The firing rate of neuronal network was affected by the stimuli patterns: compare with the spontaneous firings of neurons, after the quick electrical stimulation (10ms interval stimuli pattern), the firing rate of neuronal network increases. On the contrary, the slow electrical stimulation (100ms interval stimuli pattern) depresses the firing rate of neuronal network.

The neuronal network cultured in virto used as a important tool for brain study have been realized by more and more people owing to its non-invasive nature. But till now, there isn't a parameter that conveniently describes the changing states of neuronal network from the whole. In this paper, the synchrony calculation acted as the reactive results of the neuronal network to electrical stimulation (used for learning training) or bicuculine is analyzed and the variety of the synchrony of the network is tried as a important value to depict the diversification of the neuronal network. These experimental results processed in this way were given out in the end of the paper.

We study how the noise statistics influences the performance of separation of extracellularly recorded spikes by principal component analysis and wavelet-based technique. We show that the two approaches have different robustness against the frequency band of the experimental noise and an ppropriate filtering of the spike waveforms can significantly improve the results of separation. For the wavelet technique we suggest filter parameters optimizing spike separation. Finally we discuss a hypothesis that information encoding in neural dynamics may sometimes be considered in terms of frequency modulation.

In our paper we show, how one can obtain special class exitable systems with more complex dynamics. We discuss principal features of such models. For specific example, derived from complex nehpron model, we demonstrate new features of noisy dynamics, such as two maxima of regularity.

We study the effect of noise on a generalized mathematical model for small neural-glial ensemble. In deterministic regime, our model predicts long-term potentiation of the postsynaptic neuron as well as various calcium transients in response to the activation of glion via different pathways. Being activated by noise, the presynaptic neuron shows the irregular firing pattern. We consider how the glion (a generic glial cell) moderates the regime of the postsynaptic neuron. We observe the number of noise induced effects, such as different types of post-excitatory behavior of the postsynaptic neuron at small noise intensity and the long-term potentiation of the postsynaptic neuron at some optimal noise intensity.

Photoacoustic tomography (PAT) is a powerful medical imaging technique for medicinal diagnosis in that it combines the merits and most compelling features of light and sound to the biological tissue. It can be potentially used for the detection of the first-stage breast cancers and the blood vessel net-works in the deep depth of tissue. In this paper, a PAT experimental system constructed in our laboratory is presented by the use of 532nm wavelength light as an excitation source. By using this system, we demonstrated that it is feasible to image blood vessel networks in highly scattering ex vivo and in vivo tissue samples.

A unique dual-detector charge coupled device (CCD) system has been developed and it has been previously shown to possess a high temporal resolution and the capability to perform ratio imaging on gel phantoms. We used this CCD system to analyze differences in fluorescence intensity ratios at different levels of pH. We found that the ratio of emissions at 532 nm and 635 nm was ~3.8 in gels of pH 6.1, corresponding to cancerous tissue, and ~3.5 in gels of pH 7.2, corresponding to normal tissue. In addition, the accuracy of these intensity results was verified by calculating noise and dark current. We found that dark current intensity never exceeded 1 arbitrary unit, which is a negligible percentage of the intensity levels of the gel phantoms. Our system is very capable of accurately performing certain biomedical experiments, such as cancer detection.

Based on the experimental data obtained in vivo from digital analysis of color images of human irises, the mean melanin content in human eye irises has been estimated. For registration of the color images a digital camera Olympus C-5060 has been used. The images have been obtained from irises of healthy volunteers as well as from irises of patients with open-angle glaucoma. The computer program has been developed for digital analysis of the images. The result has been useful for development of novel and optimization of already existing methods of non-invasive glaucoma diagnostics.

Currently, to enhance light penetration into tissue and improve imaging performance for high-resolution imaging techniques, optical clearing of biological tissue is normally accomplished by the impregnation of bio-tissues with the hyperosmotically active agents. The results from previous studies appear encouraging but there is, as yet, a relatively poor understanding of the mechanisms involved. By using FT-IR imaging technique, we perform a preliminary investigation on dynamic processes occurring in hyperosmotic agents penetrating into skin tissue in vitro. The sequential collection of images in time series provides an opportunity to assess the movement of glycerol and DMSO beneath the surface of skin tissue over time. The results presented show the potential of FT-IR imaging as an analytical tool for the study on dynamic optical clearing effect when the bio-tissue is impregnated by hyperosmotic agents. A further exploration of FT-IR imaging in this regard would be desirable to quantify hyperosmotic agents used for optical clearing of different biological tissues.

We develop a Monte Carlo model for optical coherence signal simulation and providing accurate and high resolution information on the birefringence properties of the connective tissues. To understand the polarized sensitive optical coherence tomography imaging mechanism the Monte Carlo technique is generalized for simulation of polarized low-coherent back-scattering of optical radiation scattered within the randomly inhomogeneous turbid medium like the connective tissues. The results of simulation demonstrate a good agreement both with the theoretical and experimental predictions.

The technology of time-resolved diffuse optical spectroscopy to determine optical parameters of biological tissues is reviewed in this paper. The theoretical model and some the development conditions are also presented. As an example, a Monte Carlo algorithm was developed to a two-layered tissue. Based on the numerical simulation, the structure information including the optical properties of the tissue can be obtained. In addition, the prospect of time-resolved diffuse optical spectroscopy technology is commented based on our opinion.

The results of measurements of transmittance of high power laser irradiation through skull bones and scalp are presented. Dependences of transmittance on sample thickness were received. Character of transmittance was investigated and characteristics of heterogeneity of the scattering structure of the skull bones are proposed. Besides that, variation of temperature of skull and scalp surfaces under exposure of high power laser irradiation during experiments was controlled. Experimental results were verified by Monte-Carlo simulations.

Mathematical model of organelle transport by few molecular motors along filament is presented. Each motor is described as mechanochemical system, which consists of 3 elastically coupled Brownian particles and can be in different intrinsic states, jumping from one discrete filament bound site to other. Rigid or elastic coupling between motors and "cargo" are considered. Asymptotic analysis of organelle movement is performed and macroscopic parameters (average velocity and effective diffusion coefficient) are calculated.