This PDF file contains the front matter associated with SPIE Proceedings Volume 6436, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

This contribution demonstrates potential of Spectral Optical Coherence Tomography (SOCT) for studies of dynamic processes in biomedicine occurring at various time scales. Several examples from ophthalmology, optometry, surgery, neurology are given to illustrate the extension of SOCT beyond pure morphological investigations.

The mechanisms of photon propagation in random media in the diffusive multiple scattering regime have been previously studied using diffusion approximation. However, similar understanding in the low-order (sub-diffusion) scattering regime is not complete due to difficulties in tracking photons that undergo very few scatterings events. Recent developments in low-coherence enhanced backscattering (LEBS) overcome these difficulties and enable probing photons that travel very short distances and undergo only a few scattering events. In LEBS, enhanced backscattering is observed under illumination with spatial coherence length L_sc less than the scattering mean free path l_s. In order to understand the mechanisms of photon propagation in LEBS in the sub-diffusion regime, it is imperative to develop analytical and numerical models that describe the statistical properties of photon trajectories. Here we derive the probability distribution of penetration depth of LEBS photons and report Monte Carlo numerical simulations to support our analytical results. Our results demonstrate that, surprisingly, the transport of photons that undergo low-order scattering events has only weak dependence on the optical properties of the medium (l_s and anisotropy factor g) and strong dependence on the spatial coherence length of illumination, L_sc relative to those in the diffusion regime. More importantly, these low order scattering photons typically penetrate less than l_s into the medium due to low spatial coherence length of illumination and their penetration depth is proportional to the one-third power of the coherence volume (i.e. [l_s &pgr; L²_s] ^1/3).

We recently developed a new microscopic optical technique capable of noninvasive analysis of cell structure and cell dynamics on the submicron scale [1]. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light scattering spectroscopy (LSS) and is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales on the order of 100 nm. To test the ability of CLASS microscopy to monitor cellular dynamics in vivo we performed experiments with human bronchial epithelial cells treated with DHA and undergoing apoptosis. The treated and untreated cells show not only clear differences in organelle spatial distribution but time sequencing experiments on a single cell show disappearance of certain types of organelles and change of the nuclear shape and density with the progression of apoptosis. In summary, CLASS microscopy provides an insight into metabolic processes within the cell and opens doors for the noninvasive real-time assessment of cellular dynamics. Noninvasive monitoring of cellular dynamics with CLASS microscopy can be used for a real-time dosimetry in a wide variety of medical and environmental applications that have no immediate observable outcome, such as photodynamic therapy, drug screening, and monitoring of toxins.

Conventional x-ray imaging presents challenges for early detection and diagnosis, especially in areas such as mammography, where similar attenuation characteristics between malignant and normal breast tissue result in low contrast between them. An emerging technology called phase-contrast x-ray imaging has the potential to overcome this challenge by also incorporating phase shift effects, which contain more information than attenuation alone. The goal of this study was to verify through the accepted technique of contrast-detail analysis that the image quality provided by a phase-contrast prototype system is superior to that provided by a conventional imaging system. The use of a CDMAM phantom further reinforces the validity of the results, as this method has been proven to increase the accuracy, because it employs a four-alternative fixed choice method for the test objects instead of known locations. In the study, phasecontrast and conventional images of a CDMAM phantom were acquired and presented to observers for analysis. The corresponding contrast-detail curves comparing the systems demonstrate higher image quality produced by the phase-contrast system, an encouraging indication of the future of phase-contrast technology and a step forward in proving the feasibility of its introduction into a clinical environment.

Spreading depression (SD) has been found involved in focal cerebral ischemia which may result in severe or lethal neurological deficits. Electrical recording of SD has been used for acute and long term monitoring of focal cerebral ischemia but with an inherently low resolution. Here, we presented optical intrinsic signal imaging (OISI) to characterize the spontaneous SD waves following permanent middle cerebral artery occlusion (MCAO) in rats with high spatial resolution. During each SD episode, the measured optical reflectance varied regionally: decreased (-12.5±2.8%) in the area near the midline, remained flat (3.1±2.5%) in the lateral region, and increased (12.1±3.6%) in the intermediate cortex. The three types of changes yielded identifications for three biological relevant zones: nonischemic cortex, penumbra and infarct core. Accompanying recurrent SD waves, the suggested penumbral area reduced by about 6.4±2.5% of the whole imaged area per SD event, indicating a growth of the infracted area. Staining with 2% 2,3,5-triphenyltetrazolium chloride (TTC) 4 h post-occlusion proved the infarct cortex to be consistent with the lateral region where the final SD wave did not invade (r=0.86±0.10). The results suggest that OISI based on SD can effectively used to distinguish nonischemic cortex, penumbra and infarct core in the ischemic hemisphere and monitor the development of ischemia with high spatial resolution.

We present here a bird-eye view of time-dependent optical transmission of blood in red-near infrared spectral range. This issue is of the key importance both for fundamental understanding and for various applications connected with non-invasive optical blood analysis. A number of experiments measuring kinetics of blood transmission in the case of natural heart pulsations and of artificial kinetics following over-systolic occlusion is reviewed. The comprehensive theoretical approach has to consider scattering-associated mechanism rather than the widely accepted absorption-associated one. Light scattering occurs on RBC aggregates. The size of aggregates and their shape change in time due to blood flow variations. It results in the corresponding changes of optical transmission.

The tendency of red blood cells (RBCs) to aggregate is considered to be a critical biological activity, which contributes to blood viscosity. The ability to assess blood viscosity parameters non-invasively can play an important role in a variety of fields of medicine. Toward achieving this goal, we have attempted to follow the kinetics of red blood cell's aggregation process non-invasively. In this work, we have generated the optical signals of RBC aggregation and have studied them both in vitro and in vivo utilizing a dynamic light scattering (DLS) approach. The system was built and calibrated, first in vitro by using micro-sphere suspensions of known particle sizes and subsequently in vitro, on a sample of whole blood. Time dependent behavior of a function expressed in terms of autocorrelation of light intensity fluctuations was analyzed. The correspondence between in vitro aggregation tests and in vivo results was revealed and is explained in terms of modified diffusion theory and WKB approximation for light scattering mediated by aggregates. Therefore, we have demonstrated the applicability of a DLS based technique for the non-invasive measurement of blood particle sizes and blood viscosity.

The use of small animals in intravital optical microscopy is a well-established experimental model to study blood microcirculation in vivo. Recent advances in cell biology and optical techniques (e.g., lasers, CCD cameras, software, etc.) provide the basis for significant improvements with in vivo imaging. This review summarizes the latest achievements in this specific area focusing on the development of modern optical and biological platforms. This includes in vivo real time monitoring of individual cells in the context of blood flow, super-sensitive fluorescence imaging, high-speed cell imaging and light scattering techniques. The capability of these platforms has been demonstrated in live animal models (e.g., mouse and rat ear, rat mesentery, and others) for real-time monitoring of individual blood cell properties (e.g., size and shape), cell trafficking, cell-cell interactions (e.g., aggregation in flow or adhesion to vessel walls), and blood flow viscosity. Future applications are discussed including in vivo early diagnosis of disease and monitoring cellular responses to environmental and therapeutic interventions.

Regulatory dynamics of energy metabolism in living cells entails a coordinated response of multiple enzyme networks that operate under non-equilibrium conditions. Here we show that mitochondrial dysfunctions associated with the aging process significantly modify nonlinear dynamical signatures in free radical generation/removal thereby altering energy metabolism in liver cells. Combining high spatial and temporal resolution imaging and bio-energetic measurements, our work provides experimental support to the hypothesis that mitochondria manifest nonlinear dynamical behavior for efficiently regulating energy metabolism in intact cells and any partial or complete reduction in this behavior would contribute to organ dysfunctions including aging process and other disease processes.

A new mechanism is proposed for selective laser killing of abnormal cells by laser thermal explosion of single nanoparticles - "nano-bombs" - delivered to the cells. Thermal explosion of the nanoparticles is realized when the heat generates within the strongly-absorbing target more rapidly than the heat can diffuse away. On the basis of simple energy balance, it is shown that the lower level of the threshold energy density of a single laser pulse required for thermal explosion of solid gold nanospehere is about 40 mJ/cm², which is well below the safety standard for medical lasers (100 mJ/cm²) for healthy tissue and cells. The nanoparticle's explosion energy density can be reduced further (up to 11 mJ/cm²) by using gold nanorods due to higher plasmon-resonance absorption efficiency of nanorods. Additionally, the nanorods optical resonance lies in the near-IR region, where biological tissue transmissivity is the highest. Here, the effective therapeutic effect for cancer cell killing can be achieved due to nonlinear phenomena, which accompany the thermal explosion of the nanoparticles: generation of the strong shock wave with supersonic expansion of dense vapor in the cell volume, producing sound waves and optical plasma.

Upon absorption of laser energy, microparticles can convert the absorbed energy into temperature rises, pressure waves, and vaporization. All of these will affect the surrounding material as well as damaging the absorbing particle. The pressure signals display especially complex behavior because of two competing time scales: the duration of the laser pulse and the characteristic mechanical oscillation time of the absorber. As the pulse duration is lengthened, the pressure signals become increasingly more complicated. Using power spectra and Lyapunov exponents, we show that for pulse durations greater than the characteristic oscillation time, the pressure signals are chaotic. The chaotic nature of the pressure signal presents potentially dangerous uncertainty when using longer laser pulses in biomedical and engineering applications.

Quantitative analysis in systems biology often deals with noisy and complex high-dimensional problems. In genomics, for instance, measurements of gene expression changes are usually obtained through various experimental conditions, and when these conditions correspond to time points, only a few of them are usually available. This is an unfortunate fact, as with small sample sizes it becomes hard to capture any form of dependence structure in the data. Thus, key information about gene co-expression and co-regulation dynamics may be missed preventing from a reliable reconstruction of the underlying gene-gene interaction network. It is often an advantage to be able to exploit the sparsity and achieve the intrinsic dimensionality properties of biological systems under exam. Such noisy high-dimensional systems depend on complex latent dynamics that may be viewed as mixtures of informative sources with unknown statistical distribution and subject to unknown mixing mechanism. Blind source separation techniques, fuzzy rules, embedding principles and entropic measures represent useful methodological tools for disentanglement of the dynamics. We report results from data obtained by perturbation experiments and gene network reconstruction and inference.

Probability properties of one-dimensional piece-wise linear chaotic map having two linear brunches (Rényi map) are investigated. The map dynamics depends on a parameter defining substantially view of the map, i.e. slopes of map linear branches and proportion between them. This dependence is very sensitive, and there is the infinite set of parameter values providing existence of piecewise constant invariant density of the map. These values of the parameter may be obtained by solving corresponding algebraic equation. These properties allow us to apply the map for modeling complex chaotic regimes by means of switching between various values of parameter. The map is suggested to be suitable for description of degrees of chaotic neuron reactions on weak excitations and for chaotic encryption.

In order to discuss the relative factors affecting the optical clearing effect of agents on skin tissues, six hydroxy-terminated and saturated alcohols with different refractive index and molecular weight were chosen as the optical clearing agents (OCAs). After being treated by different OCAs, the change of transmitted intensity of porcine skins in vitro was measured by single integrating sphere system. The results showed the optical clearing effects of six OCAs, i.e., glycerol, PEG400, PEG200, 1,3-propylene glycol, 1,4-butanediol and 1-butanol, arranged in the descending order. Based on the above results, the refractive index and molecular weight was further discussed. The optical clearing effect of alcohols has been deduced to have negative correlation with refractive index (r=-0.608), but no correlation with molecular weight (r= 0.008).

Two-photon fluorescence microscopy is a powerful technique to obtain the stacks of neuronal individual or population morphologies deep inside brain tissue in vivo. However, the stacks often suffer from increasing noises with depth because of light scattering of specimen and optical distortion of microscopic system. Therefore, deconvolution becomes a more useful and a crucial approach to restore the original details of neuronal structure in fluorescence images. Since Richardson-Lucy deconvolution algorithm is appropriate for Poisson process of microscopy but sensitive to noise, we propose a scheme that it pre-filters noise via Perona-Malik nonlinear anisotropic diffusion before performing regularized Richardson-Lucy deconvolution algorithm. In contrast to other restoration approaches, the preliminary denoising of Perona-Malik diffusion model provides a better trade-off between noise reduction and edge preservation, and helps to following regularized Richardson-Lucy deconvolution procedure. Experimental results have shown that proposed scheme is effective and robust for restoring noisy two-photon fluorescence images.

Flow plays an important role during the early development of embryogenesis. Traditionally, ultrasound is used for embryonic flow monitoring. Ultrasound is sensitive to blood flow, however relatively low resolution (~100 um) refrains its usage in this area since normally the heart outflow tract of the early embryo is only a few hundred microns. Spectral optical coherence tomography (SOCT), with high resolution, high acquisition speed and high dynamic range, has been widely used in biological tissue imaging in recent years. By evaluation of phase difference between consecutive A-scan lines, spectral optical coherence tomography provides the ability for flow measurement. Thus, spectral optical coherence tomography has many advantages to ultrasound in early embryo flow measurement. In order to monitor the blood flow within the outflow tract (OFT) of an early stage chicken embryo, two spectral optical coherence tomography setups were built in our lab with different central wavelength, i.e. 840nm and 1300nm. The performances of the two systems is compared, including axial resolution, transverse resolution, penetration depth, measurable depth, maximum Doppler shift frequency and maximum measurable projection flow velocity. Chicken embryo heart OFT images were acquired using both the two systems. By comparison, the system with 1300nm wavelength is more suitable for this application since it has sufficient penetration depth.

We study mechanisms of information processing in the principalis (Pr5), oralis (Sp5o) and interpolaris (Sp5i) nuclei of the trigeminal sensory complex of the rat under whisker stimulation by short air puffs. After the standard electrophysiological description of the neural spiking activity we apply a novel wavelet based method quantifying the structural stability of firing patterns evoked by a periodic whisker stimulation. We show that the response stability depends on the puff duration delivered to the vibrissae and differs among the analyzed nuclei. Pr5 and Sp5i exhibit the maximal stability to an intermediate stimulus duration, whereas Sp5o shows "preference" for short stimuli.

It is known that glucose influences on spectral properties of blood and hemoglobin and interacts with plasma proteins and hemoglobin in erythrocytes. Changes of optical properties of blood and hemoglobin at glucose concentration within physiological level are important for diagnosis and monitoring of diabetes. The purpose of this study is to investigate the effect of presence of glucose and glycation of hemoglobin on absorbance of aqueous hemoglobin solutions with different glucose concentrations. Measurements were taken using spectrophotometer EQUINOX 55 (Bruker Optic GmbH) in a range 1000-1800 nm. Water has absorption bands in the near-infrared region which may be influenced by glucose presence. We have hypothesized that glucose and hemoglobin, especially glycated hemoglobin, may influence the absorption band of water in solution. The hemoglobin solutions with different amount of glucose (from 0 to 1000 mg/dl with a step 100 mg/dl) were incubated up to 28 days. Our measurements show that presence of glucose affects the spectra of aqueous hemoglobin solutions. The magnitude of absorbance depends on glucose concentration. At the beginning of incubation hemoglobin solution without glucose has the lowest absorbance magnitude, but after a rather long time of incubation (28 days) the absorbance of hemoglobin solutions with glucose become smaller compared to the absorbance of hemoglobin solution without glucose. This fact may be explained by assumption of hemoglobin glycation, when glucose molecules chemically bind to hemoglobin, and water binding to hemoglobin. In the case of water binding to hemoglobin molecules the amount of free water molecules in solution decreases, so the water aborbance is excepted to decrease.

Dynamics of glucose concentration in human organism is an important diagnostic characteristic for it's parameters correlate significantly with the severity of metabolic, vessel and perfusion disorders. 36 patients with stable angina pectoris of II and III functional classes were involved in this study. All of them were men in age range of 45-59 years old. 7 patients hospitalized with acute myocardial infarction (aged from 49 to 59 years old) form the group of compare. Control group (n = 5) was of practically healthy men in comparable age. To all patients intravenous glucose solution (40%) in standard loading dose was injected. Capillary and vein blood samples were withdrawn before, and 5, 60, 120, 180 and 240 minutes after glucose load. At these time points blood pressure and glucose concentration were measured. In prepared blood smears shape, deformability and sizes of erythrocytes, quantity and degree of shear stress resistant erythrocyte aggregates were studied. Received data were approximated by polynomial of high degree to receive concentration function of studied parameters, which first derivative elucidate velocity characteristics of morphofunctional erythrocyte properties during intravenous glucose injection in patients with coronary heart disease and practically healthy persons. Received data show principle differences in dynamics of morphofunctional erythrocyte properties during intravenous glucose injection in patients with coronary heart disease as a possible mechanism of coronary blood flow destabilization.

Blood cell-cell and cell-vessel wall interactions are one of the key patterns in blood and vascular pathophysiology. We have chosen the method of reconstruction of pulsative blood flow in vitro in the experimental set. Blood flow structure was studied by PC integrated video camera with following slide by slide analysis. Studied flow was of constant volumetric blood flow velocity (1 ml/h). Diameter of tube in use was comparable with coronary arteries diameter. Glucose solution and unfractured heparin were used as the nonspecial irritants of studied flow. Erythrocytes space structure in flow differs in all groups of patients in our study (men with stable angina pectoris (SAP), myocardial infarction (MI) and practically healthy men (PHM). Intensity of erythrocytes aggregate formation was maximal in patients with SAP, but time of their "construction/deconstruction" at glucose injection was minimal. Phenomena of primary clotting formation in patients with SAP of high function class was reconstructed under experimental conditions. Heparin injection (10 000 ED) increased linear blood flow velocity both in patients with SAP, MI and PHP but modulated the cell profile in the flow. Received data correspond with results of animal model studies and noninvasive blood flow studies in human. Results of our study reveal differences in blood flow structure in patients with coronary heart disease and PHP under irritating conditions as the possible framework of metabolic model of coronary blood flow destabilization.

Subthreshold oscillations can be found in different neural systems. Some mathematical models of bursting neurons also manifest slow oscillations that are more or less independent from fast spiking process and becomes subthreshold when spiking subsystem is set in excitable regime. Because neural activity is known to be heavily influenced by a variety of noisy processes, it is important to understand how the subthreshold oscillations can change the response of neural system on noisy stimulus. It is typically assumed that generation of spike does not affect slow subsystem. However, such one-way connection between slow and fast subsystems is not the case for many neural models where fast and slow ionic currents share the same equation for transmembrane potential (for example, well known Huber-Braun model). Definitely, the generation of fast action potential can affect the slow ionic currents. Thus, being excited by noise, such neural system could show different firing patterns depending on how slow subsystem is affected by the fast one. To address this problem we propose the generalized model consisting of two FitzHugh-Nagumo systems that are set in different operating regimes and thus play the role of fast excitable and slow self-sustained subsystems. With this model, we study how the noise-induced firing patterns depend on different variants of fast-to-slow coupling between subsystems. The corresponding changes in ISI distribution as well as underlying nonlinear mechanisms are discussed.

This study is focused on the determination of the absorption coefficients of oxyhemoglobin and deoxyhemoglobin solutions (1.6g/l) at different concentrations of glucose (from 0 to 1000 mg/dl with a step 100 mg/dl) from a few hours to over two week of incubation. The absorption coefficients were determined using transmittance measurements at the wavelength range from 500 nm to 1000 nm.

We report the use of a chemically etched tapered single mode fiber tip for enhancing lateral resolution in optical coherence tomography (OCT). The important advantage of this approach is that high lateral resolution is achieved, without compromising the depth of imaging, as is the case with the use of high numerical aperture (NA) objectives. Use of the tapered tip in the sample arm of a single mode fiber based set-up allowed visualization of intracellular structures of Elodea densa plant leaf that could not be seen by the conventional OCT.

Result of Monte Carlo simulations of skin optical clearing is presented. The model calculations were carried out with the aim of studying of spectral response of skin under immersion liquids action and calculation of enhancement of light penetration depth. In summary, we have shown that: 1) application of glucose, propylene glycol and glycerol produced significant decreasing of light scattering in different skin layers; 2) maximal clearing effect will be obtained in case of optical clearing of skin dermis, however, absorbed light fraction in skin dermis changed insignificantly, independently from clearing agent and place it administration; 4) in contrast to it, the light absorbed fraction in skin adipose layer increased significantly in case of optical clearing of skin dermis. It is very important because it can be used for development of optical methods of obesity treatment.

A method for rapid reconstruction of optical properties, such as the absorption and scattering coefficients of the thin layered tissue from diffuse reflection, is introduced. As the diffusion-approximation-based approaches are not applicable in the case of small source-detector separation, Monte-Carlo (MC) method is chosen as the forward model to simulate the photon migration in the transport regime. A flexible and fast perturbation model of diffuse reflectance has been developed for the extraction of the information of photon migration in tissue from MC model. With the derived photon migration information, the inverse problem for obtaining the optical properties was solved by a Gauss-Newton nonlinear least-squares algorithm. Simulation results show that the proposed method is valid for a wide range of optical properties and the related measurement can be simple and adaptable. Experimental demonstration was performed on a set of liquid phantoms in a wide range of absorption coefficients and reduced scattering coefficients and with CW measurements in different optode separations. The results show that, with the developed method, the optical properties calculated from the experimental data deviate form the "true value" by no more than 10%.