This PDF file contains the front matter associated with SPIE Proceedings Volume 7898, including the Title Page, Copyright information, Table of Contents, Introduction, Report on the Panel Discussion, and the Conference Committee listing.

Impaired muscular microcirculation in lower extremities is common in many peripheral vascular diseases (PVD), especially the peripheral arterial disease (PAD). There is a need for an imaging method that can be used to noninvasively visualize depth-resolved microcirculation within muscle tissues. Optical microangiography (OMAG) is a recently developed label-free imaging method capable of producing 3D images of dynamic blood perfusion within micro-circulatory tissue beds at an imaging depth up to ~2 mm, with an imaging sensitivity to the blood flow at ~160 μm/s. In this paper, we demonstrate the utility of OMAG in imaging the detailed blood flow distributions, at microcirculatory level resolution, within skeletal muscles in mice. By use of the mouse model of hind-limb ischemia, we show OMAG can assess the perfusion changes caused by ligation. These findings indicate that OMAG is a promising technique to effectively study skeletal muscle-related vascular disease and their pharmacologic therapies.

Preservation of porcine aortic tissue at 4°C in phosphate buffered saline (PBS) was monitored for a period of 10 days. Optical coherence tomography (OCT) was used to indirectly quantify the permeation of glucose, with the objective of assessing the structural integrity of the tissue. The average permeability rate for the first day was calculated to be (2.32 ± 0.46) × 10^-5 cm/s. After 10 days of storage the average permeability rate was found to be (7.37 ± 0.41) × 10^-5 cm/s -- nearly a 200% increase. A z-test performed on the permeability rate results verified that after 4 days of storage the permeability rate had significantly changed (p<0.05). Histology was used to validate the OCT results by quantifying changes in pore area. An increase in pore size paralleled the increase in permeability rate over the 10 day storage period. A parallel experiment demonstrated that increasing pore size was not accompanied by release of protein from the tissue over the storage period. The results suggest that tissues can maintain their structural stability for at least three days at 4°C in PBS.

Tendons are load-bearing collagenous tissues consisting mainly of type I collagen and various proteoglycans (PGs) including decorin and versican. It is widely accepted that highly orientated collagen fibers in tendons a play critical role for transferring tensile stress and demonstrate birefringent optical properties. However, the influence that proteoglycans have on the optical properties of tendons is yet to be fully elucidated. Tendinopathy (defined as a syndrome of tendon pain, tenderness and swelling that affects the normal function of the tissue) is a common disease associated with sporting injuries or degeneration. PG's are the essential components of the tendon extracellular matrix; changes in their quantities and compositions have been associated with tendinopathy. In this study, polarization sensitive optical coherence tomography (PS-OCT) has been used to reveal the relationship between proteoglycan content/location and birefringent properties of tendons. Tendons dissected from freshly slaughtered chickens were imaged at regular intervals by PS-OCT and polarizing light microscope during the extraction of PGs or glycosaminoglycans using established protocols (guanidine hydrochloride (GuHCl) or proteinase K solution). The macroscopic and microscopic time lapsed images are complimentary; mutually demonstrating that there was a higher concentration of PG's in the outer sheath region than in the fascicles; and the integrity of the sheath affected extraction process and the OCT birefringence bands. Extraction of PGs using GuHCl disturbed the organization of local collagen bundles, which corresponded to a reduction in the frequency of birefringence bands and the band width by PS-OCT. The feature of OCT penetration depth helped us to define the heterogeneous distribution of PG's in tendon, which was complimented by polarizing light microscopy. The results provide new insight of tendon structure and also demonstrate a great potential for using PS-OCT as a diagnostic tool to examine tendon pathology.

Optical spectroscopy approach, using non-coherent light sources, has become an important tool for non-invasive analysis in vivo. It is based on the assumption that biochemical characteristics of biological system can be determined through the optical coefficients of blood and tissue particles. Thus, in the framework of this approach, the major concern is to express the obtained optical signals in terms the optical coefficients of the single particle of blood or tissue. However, since the light propagation in tissue is dominated by the multiple-scattering component, a direct measurement of single scattering characteristics turns to be a very difficult task. Practically, only the relative changes of absorption and scattering coefficients are measured. We suggested to adopt the dynamic light scattering (DLS) or speckle technique for the determination of the light scattering coefficients of the red blood cells under stasis conditions in vivo. We assumed that under zero flow conditions the RBC movement is driven mostly by the Brownian motion. It was shown, that under appropriate measurement geometry, the measured optical signal can be decomposed into a few major components. The most dominant components are ascribed to the single backscattering and forward scattering coefficients of the red blood cells. In-vitro and in vivo experimental tests have shown a good correspondence between the theoretically estimated and experientially measured results. The obtained results indicate that the DLS technique can be adopted for the determination of blood particles scattering characteristics in addition to the movement and effective viscosity parameters measurement in vivo.

In this study, we aims to evaluate the capability of a new developed laser speckle contrast imaging (LSCI) system for mapping microvascular perfusion and to demonstrate the capability of LSCI to assess transient change of blood perfusion with high flow sensitivity. Through well defined phantom experiments, we found that there is a critical point that divides the velocity domain into two halves, one half that is below the critical point where the higher the velocity, the higher the speckle contrast is; and it is however opposite in the other half. Our study shows that the increasing of the camera exposure time value causes decreasing of the critical point value. For the first time, this finding is proposed and provides a novel explanation about the laser speckle temporal contrast imaging (LSTCI). To further validate, measurements were performed on mouse ear flap during occlusion of the root artery circulation to modify the whole mouse ear flap perfusion. Finally, the speckle contrast maps of dynamic microvascular blood flow in the mouse ear flap were demonstrated. The promising results show that the LSCI system can give useful information as to blood flow change.

Recent success in reconciling laser Doppler and speckle measurements of dermal perfusion by the use of multi-exposure speckle has prompted an investigation of speckle effects arising from directed blood flow which might be expected in the small blood vessels of the eye. Unlike dermal scatter, the blood in retinal vessels is surrounded by few small and stationary scatterers able to assist the return of light energy by large-angle scatter. Returning light is expected to come from multiple small angle scatter from the large red blood cells which dominate the fluid. This work compares speckle measurements on highly scattering skin, with measurements on flow in a retinal phantom consisting of a glass capillary which is itself immersed in an index matching fluid to provide a flat air-phantom interface. Brownian motion dominated measurements when small easily levitated scatters were used, and flow was undetectable. With whole-blood, Brownian motion was small and directed flows in the expected region of tens of mm/s were detectable. The nominal flow speed relates to the known pump rate; within the capillary the flow will have a profile reducing toward the walls. The pulsatile effects on laser speckle contrast in the retina are discussed with preliminary multi-exposure measurements on retinal vessels using a fundus camera. Differences between the multiple exposure curves and power spectra of perfused tissue and ordered flow are discussed.

Laser speckle and laser Doppler perfusion measurements apply different analyses to the same physical phenomenon and so should produce the same results. However, there is some evidence that laser Doppler can measure perfusion at greater depths than laser speckle. Using phantom measurements and comparison to spatially modulated imaging, we show why this might be the case. Various implementations of imaging laser Doppler and speckle systems have different optical setups, producing different effective distances between the illumination and detector points on the surface of the tissue. Separating the effective source and detector regions in tissue measurements biases the measurements towards deeper tissues, and when the effective source and detector regions coincide, the measurement is biased towards surface tissues. Probe-based or scanning laser Doppler systems with point illumination can separate the source and detector regions to interrogate deeper tissues, while whole-field imaging laser Doppler systems and laser speckle contrast systems have broad illumination covering the measurement areas. The volume of tissue informing a measurement at any point in a whole-field system, and hence the depth sensitivity, is determined by the optical properties of the tissue at the working wavelength.

The kinetics of resin composite polymerization plays an important, though not well understood, role it the development of shrinkage stress and the resultant integrity of the final restoration. In this report we investigate the effect of curing irradiance on the polymerization kinetics using a dynamic light scattering technique known as laser speckle contrast analysis (LSCA). Thin layer samples are considered with focus given to the effect of sample thickness on the rate results obtained with this method. We present results for the intensity fluctuation rate as a function of irradiance for two statistical models of intensity decorrelation: Lorentzian and Gaussian. Results indicate that the rate of scatterer motion varies approximately with the square root of irradiance, which agrees well with theory and previous results in the literature. Our results suggest that dynamic light scattering techniques, and LSCA in particular, provide an effective, non-contact means of assessing polymerization kinetics.

Laser speckle contrast imaging (LSCI) is becoming an established method for full-field imaging of blood flow dynamics in animal models. Blood flow pulsation originated from heart beat affects blood flow measurement results of LSCI and it is considered as major physiology noise source for most biomedical applications. But in some biomedical applications, the details of the pulsation process might provide useful information for disease diagnostics. In this study, we investigated the ability as well as the limitation of LSCI in monitoring flow pulsation in phantom study. Both intralipid (2% - 5%) and human whole blood samples are used in phantom study. A syringe pump is controlled by a computer-programmable motor controller and liquid phantom is pushed through a 400 μm ID capillary tube by the pump at different pulsation patterns, varied in frequency (1-7 Hz), valley-to-peak ratio (10%-50%), acceleration/deceleration rate, etc. Speckle contrast images are acquired at 15-30 frames-per-seconds. Our results show: (1) it is very hard for LSCI to pick up signals from high frequency pulsation (5-7 Hz), which is close to the heart back frequency of rats. This might be caused by the nature of fluid dynamics of blood during pulsation. LSCI might not work well for animal models in detecting pulsation. (2) With low frequency pulsation (1 Hz, close to human normal pulsation rate), our experimental results shows from most pulsation patterns, LSCI could catch the fine details of the blood flow change in a cycle. LSCI might be used for studying human blood flow pulsation.

Micro-CT scans generate three-dimensional images consisting of the order of 1000³ voxels (3D picture elements), each cubic voxel being sub-micron to 100 micrometer on a side. The gray-scale modulation within tomographic images reflects the local attenuation of the x-ray. This allows for differentiation of different tissues by virtue of their elemental content. However, the elements in blood vessel walls and within blood differ little from organ parenchyma, hence they are not readily distinguishable unless the attenuation of blood is enhanced by injecting a heavy element (such as iodine) into the blood stream or by staining the vessel wall tissues with heavy metals such as osmium tetroxide. Three-dimensional micro-CT images a volume (of light-opaque tissue) large enough to include entire, intact, vascular trees without the need to destroy the 3D tissue specimen. Hence, the fluid dynamic and the perfusion territory size consequences, as well the micro-anatomic relationship of the vascular branching geometry and interconnectivity to parenchymal structures (e.g., nephron, hepatic lobule or cancer) can be readily appreciated and quantified. The permeability of microvasculature can also be imaged by virtue of the increased contrast resulting from the fraction of the injected contrast agent passing through the endothelium into the surrounding extravascular tissue. In recent years micro-CT based on the imaging of coherent x-ray scatter and on x-ray phase shift caused by local electron density distributions (reflecting molecular bond type in some cases) provide greater inherent image contrast than does x-ray attenuation. These new capabilities are now active avenues of research and development.

We introduce a new type of Optical Microangiography (OMAG) called Quantifiable Optical Microangiography (QOMAG) which is capable of performing quantitative flow imaging with smart velocity ranging. In order to extracting multi-range velocity, two three dimensional data sets need to be acquired at the same imaging area. One data set performs dense scanning in B-scan direction and Doppler analysis was done at the basis of subsequent A-scans, while the other data set performs dense scanning in C-scan direction and Doppler analysis was done at the basis of consecutive B-scan. Since the velocity ranging is determined by the time interval between consecutive measurements of the spectral fringes, longer time interval will give us higher sensitivity to slow velocity. By simultaneous acquiring data sets with different time intervals, we can perform smart velocity ranging quantification on blood flow characterized by different velocity values. The feasibility of QOMAG for variable blood flow imaging is demonstrated by in vivo studies executed on cerebral blood flow of mouse model. Multi-range detailed blood flow map within intracranial Dura mater and cortex of mouse brain can be given by QOMAG.

We present a multi-modal optical diagnostic approach utilizing a combined use of Fluorescence Intravital Microscopy and Dynamic Light Scattering for in vivo functional imaging of tumor vascular network and blood microcirculation. Fluorescence Intravital Microscopy is used for imaging of tumor and tumor surroundings, whereas Dynamic Light Scattering is applied for imaging of vascular network and blood microcirculation. The obtained results demonstrate that presented multi-modal imaging approach has a great potential in vascular biology and can significantly expand the capabilities of tumor angiogenesis studies and notably contribute to the development of cancer treatment.

The microcirculation plays a critical role is maintaining organ health and function by serving as a vascular are where trophic metabolism exchanges between blood and tissue takes place. To facilitate regular assessment in vivo, noninvasive microcirculation imagers are required in clinics. Among this group of clinical devices, are those that render microcirculation morphology such as nailfold capillaroscopy, a common device for early diagnosis and monitoring of microangiopathies. However, depth ambiguity disqualify this and other similar techniques in medical tomography where due to the 3-D nature of biological organs, imagers that support depth-resolved 2-D imaging and 3-D image reconstruction are required. Here, we introduce correlation map OCT (cmOCT), a promising technique for microcirculation morphology imaging that combines standard optical coherence tomography and an agile imaging analysis software based on correlation statistic. Promising results are presented of the microcirculation morphology images of the brain region of a small animal model as well as measurements of vessel geometry at bifurcations, such as vessel diameters, branch angles. These data will be useful for obtaining cardiovascular related characteristics such as volumetric flow, velocity profile and vessel-wall shear stress for circulatory and respiratory system.

There exist numerous planar imaging methods for mapping the human microvasculature. In medical diagnostics, tomography is preferred over surface imaging for the simple reason that biological organs are 3-dimensional in nature. The aim of this work is to create a novel technique to non-invasively map the concentration of red blood cells in the human microcirculation allowing 3-dimensional image reconstruction. We propose a tomographic system which is based on absorption contrast imaging. A Michelson interferometry method is employed using a broadband, white light source. This work details preliminary results of the calibration procedure of a 'bulk' system. A mirror, reflectance standards, glass-mirror arrangement, and color filter arrangement were used as samples. The resultant interference patterns from each were imaged and analyzed.

Non-invasive tumor microvasculature visualization and characterization play significant roles in the detection of tumors and importantly, for aiding in the development of therapeutic strategies. The feasibility and effectiveness of a Doppler variance standard deviation imaging method for tumor angiogenesis on chorioallantoic membrane were tested in vivo on a rat glioma F98 tumor spheroid. Utilizing a high resolution Doppler Variance Optical Coherence Tomography (DVOCT) system with A-line rate of 20 kHz, three-dimensional mapping of a tumor with a total area of 3×2.5mm² was completed within 15 seconds. The top-view image clearly visualized the complex vascular perfusion with the detection of capillaries as small as approximately 10μm. The results of the current study demonstrate the capability of the Doppler variance standard deviation imaging method as a non-invasive assessment of tumor angiogenesis, with the potential for its use in clinical settings.

The goal for this study is to examine cerebral autoregulation in response to a repeated sit-stand maneuver using both diffuse functional Near Infrared spectroscopy (fNIRS) and Transcranial Doppler sonography (TCD). While fNIRS can provide transient changes in hemodynamic response to such a physical action, TCD is a noninvasive transcranial method to detect the flow velocities in the basal or middle cerebral arteries (MCA). The initial phase of this study was to measure fNIRS signals from the forehead of subjects during the repeated sit-stand protocol and to understand the corresponding meaning of the detected signals. Also, we acquired preliminary data from simultaneous measurements of fNIRS and TCD during the sit-stand protocol so as to explore the technical difficulty of such an approach. Specifically, ten healthy adult subjects were enrolled to perform the planned protocol, and the fNIRS array probes with 4 sources and 10 detectors were placed on the subject's forehead to detect hemodynamic signal changes from the prefrontal cortex. The fNIRS results show that the oscillations of hemoglobin concentration were spatially global and temporally dynamic across the entire region of subject's forehead. The oscillation patterns in both hemoglobin concentrations and blood flow velocity seemed to follow one another; changes in oxy-hemoglobin concentration were much larger than those in deoxyhemoglobin concentration. These preliminary findings provide us with evidence that fNIRS is an appropriate means readily for studying cerebral hemodynamics and autoregulation during sit-stand maneuvers.

Method of the lag/latency time (LT) measurement, calculation and interpretation can be simultaneously applied to study in vivo glucose diffusion from the capillary to the skin tissue, to calibrate spectroscopically measured glucose levels during real-time glucose monitoring of dynamic processes in the skin tissue and to study glucose optical properties in the living skin tissue. Based on previous reports on determining interstitial glucose levels and their LT's by HATR-FTIR spectroscopy, here the LT was calculated for each glucose absorbance level at about 1030-41, 1080, 1118 and 1153 cm^-1 during oral glucose tolerance test (OGTT) with different doses (5g, 20g, 75g). The LT showed dose-dependency and described intra-/inter-subject changes of skin glucose dynamics in healthy and diabetes subjects. The time required for glucose to diffuse from the capillary to the skin tissue was shorter in a diabetes subject, than in a healthy subject, independently on intaken dose of glucose. Nevertheless, in both subjects the LT changes ranged within 0–50 minutes. Measurement of the LT demonstrated a potential to provide insight to healthy and diabetic glucose dynamics between the blood and interstitial fluid compartments in the upper layer of the skin tissue. Also, the LT might be regarded as a method to calibrate dynamic measurements of glucose in vivo by this spectroscopy method and to characterize living skin tissue glucose optical properties.

Adequate functioning of the peripheral micro vascular in human skin is necessary to maintain optimal tissue perfusion and preserve normal hemodynamic function. There is a growing body of evidence suggests that vascular abnormalities may directly related to several dermatologic diseases, such as psoriasis, port-wine stain, skin cancer, etc. New in vivo imaging modalities to aid volumetric microvascular blood perfusion imaging are there for highly desirable. To address this need, we demonstrate the capability of ultra-high sensitive optical micro angiography to allow blood flow visualization and quantification of vascular densities of lesional psoriasis area in human subject in vivo. The microcirculation networks of lesion and non-lesion skin were obtained after post processing the data sets captured by the system. With our image resolution (~20 μm), we could compare these two types of microcirculation networks both qualitatively and quantitatively. The B-scan (lateral or x direction) cross section images, en-face (x-y plane) images and the volumetric in vivo perfusion map of lesion and non-lesion skin areas were obtained using UHS-OMAG. Characteristic perfusion map features were identified between lesional and non-lesional skin area. A statistically significant difference between vascular densities of lesion and non-lesion skin area was also found using a histogram based analysis. UHS-OMAG has the potential to differentiate the normal skin microcirculation from abnormal human skin microcirculation non-invasively with high speed and sensitivity. The presented data demonstrates the great potential of UHS-OMAG for detecting and diagnosing skin disease such as psoriasis in human subjects.

Optical coherence tomography (OCT) has been used as part of a ground breaking translational study to shed some light on one of the worlds most prevalent autoimmune diseases; psoriasis. The work successfully integrates the fields of optical imaging, biochemistry and dermatology in conducting a dermal microdialysis (DMD) trial for quantitative histamine assessment amongst a group of psoriasis sufferers. The DMD process involves temporary insertion of microscopic hollow tubes into a layer of skin to measure the levels of histamine and other important biological molecules in psoriasis. For comparison purposes, DMD catheters were implanted into healthy, peri-lesional and lesional skin regions. The catheters' entry and exit points and their precise locations in the epidermal layer of the skin were confirmed using OCT thus obtaining high resolution, wide-field images of the affected skin as well as catheter placement whilst local microdialysis enabled a tissue chemistry profile to be obtained from these three skin regions including histamine, a local immune system activator known to contribute towards itch and inflammation. Together these tools offer a synergistic approach in the clinical assessment of the disease. In addition, OCT delivered a non-invasive and rapid method for analyzing the affected skin architecture.

Laser ultrasonic technique has the potential as an access for quantifying skin property for diagnosis and accurate assessment for skin diseases. This paper presents a finite element (FE) modelling technique which studies the effect laser wavelength has on the generated surface acoustic waveforms in a multilayered skin model. By comparison, this paper discusses the suitability of using laser generated surface waveforms for the accurate non-destructive evaluation of skin layer mechanical and geometrical properties using surface wave phase velocity analysis.

Collagen and elastin fibers are generally arranged in parallel bundles within the dermis. These bundles are oriented such that they can most efficiently resist the stress and strain that normally occurs on the skin during movement. The pattern of these fiber bundles establishes the lines of cleavage of the skin. Knowledge of the orientation of these is of key importance for surgical procedures. When incisions are cut parallel to the cleavage line orientation the incision will heal better and produce less scaring. In this work we report a novel application of Optical coherence tomography for the determination of cleavage line orientation in in-vivo human skin. The technique operates by pressing a small circular indenter onto the skin to deform the skin. This is then imaged using optical coherence tomography. Analysis of the resulting deformation can be seen to have an ellipsoidal shape which is related to the cleavage line orientation. We demonstrate that the technique can be used to map the cleavage line orientation in-vivo.

Live cells display a constant vertical motility due partly to a constant rearrangement of focal contacts and to cell shape fluctuations. This cellular micromotion has been clearly demonstrated with electric cell impedance sensing (ECIS) on 2D micro-electrodes, and correlated to cell vitality. In this study we investigated if optical coherence phase microscopy (OCPM) was able to report phase fluctuations of adult stem cells in 2D and 3D that could be correlated to cell motility. An OCPM has been developed around a Thorlabs engine (λο=930nm FWHM: 90nm) and integrated in an inverted microscope with a custom scanning head. Human adipose derived stem cells (ADSCs, Invitrogen) were cultured in Mesenpro RS medium and seeded either on ECIS arrays, 2D cell culture dishes, or in 3D highly porous microplotted polymeric scaffolds. ADSC motility was measured by ECIS and a spectral analysis was performed to retrieve the power spectral density (PSD) of the fluctuations. Cells in standard media and fixed cells were investigated. The same conditions were then investigated for ADSCs in 2D and in 3D with optical coherence phase microscopy. Significant differences were found in phase fluctuations between the different conditions, which correlated well with ECIS experiments. These preliminary results indicated that optical coherence phase microscopy could assess cell vitality in 2D and potentially in 3D microstructures.

Measurements of optical properties of fingernail and underlying tissues using OCT are presented. Review and measurements of Raman spectra of tissue and phantom compounds were done. Updating of modeling algorithm for scattering coefficient calculation on the basis of integrating sphere measurements accounting for particle size-distribution was also done. The adequate fingernail and underlying tissue optical model at 830 nm was evaluation. Tissue phantoms potentially suitable for calibration of Raman instrumentation for glucose sensing were designed and tested on the basis of epoxy resin, TiO₂-nanoparticles and micron-sized silica particles with the capillary net-work.

It is necessary to get optical information within tissue in order to improve the application of non-invasive blood glucose sensing. However, the light penetration depth is seriously limited due to high scattering effects of biological tissues, which restricts the detection precision of non-invasive blood glucose sensing. Tissue optical clearing technique is one of the effective approaches to reduce the scattering effect and increase the light penetration depth into biological tissues. In this talk, it is our aim to study the preliminary application of optical clearing to non-invasive blood glucose sensing based on Monte Carlo simulation. Firstly, optical properties of intralipid solutions mixing with different concentration of glucose were calculated within the wavelengths of 1000~1700nm. The transmittance spectra of intralipid solutions with and without glycerol as optical clearing agent were investigated through Monte Carlo simulation. Different concentrations of glycerol were taken into account. Furthermore, the root mean square error of prediction (RMSEP) was obtained by performing partial least squares (PLS) modelling. Simulation results showed that the transmittance increased gradually with the increase of glycerol concentration, which suggested that the optical clearing effect appeared. Meanwhile, the RMSEP decreased as the glycerol concentration increased. RMSEP has improved by 30.91% in the simulation, which showed the great potential of tissue optical clearing technique to effectively improve the predicting precision of non-invasive blood glucose sensing.

Low-frequency fluctuations in the laser Doppler flow signal (LDFS) from the skin are related to microvascular mechanisms of flow control. Wavelet spectral analysis has been used to correlate fluctuations in the LDFS with the endothelial, neurogenic and myogenic mechanisms of control in the frequency intervals 0.005-0.02 Hz, 0.02-0.06 Hz and 0.06-0.16 Hz, respectively. Generally the signal power, in each frequency interval, derived from the respective wavelet coefficients, is used as a measure of the activity of the related mechanism of microvascular control. However, the time-domain characteristics of the fluctuations in the LDFS in each frequency interval are poorly known. As a consequence, there is a lack of objective criteria to properly measure, in each frequency interval, the related hemodynamic parameters. Here a time-domain method is proposed to analyze and quantify fluctuations in the LDFS in each frequency band. Baseline (32 degrees Celsius) and thermally stimulated (42 degrees Celsius) LDFS of forearms from 15 healthy volunteers were collected and analyzed. The data obtained indicate that inappropriate time windows, frequently used for measurements, increase the variability of the measured signal power, diminishing the capability of the method when assessing microvascular dynamics and dysfunctions. To overcome this limitation, an objective method to measure the LDFS power in each frequency band is proposed.

Optical hemodynamic imaging employed in pre-clinical studies with high spatial and temporal resolution is significant to unveil the functional activities of brain and the mechanism of internal or external stimulus effects in diverse pathological conditions and treatments. Most current optical systems only resolve hemodynamic changes within superficial macrocirculatory beds, such as laser speckle contrast imaging; or only provide vascular structural information within microcirculatory beds, such as multi-photon microscopy. In this study, we introduce a hemodynamic imaging system based on Optical Micro-angiography (OMAG) which is capable of resolving and quantifying 3D dynamic blood perfusion down to microcirculatory level. This system can measure the optical phase shifts caused by moving blood cells in microcirculation. Here, the utility of OMAG was demonstrated by monitoring the hemodynamic response to alcohol administration in mouse prefrontal cortex. Our preliminary results suggest that the spatiotemporal tracking of cerebral micro-hemodynamic using OMAG can be successfully applied to the mouse brain and reliably distinguish between vehicle and alcohol stimulation experiment.

There is a growing body of studies suggesting that NIR spectroscopy is feasible to be used to non-invasive blood glucose sensing. However, previous results reported that blood components are very complicated and in which glucose concentration is relatively low. This feature limited the practical application of NIR spectroscopy to in vivo blood glucose detection. This talk aims to elucidate how the cholesterol influences blood glucose sensing. Spectroscopic measurements show that cholesterol appears the similar absorbance peaks to those of glucose within NIR range. Furthermore, PLS modelling results demonstrate that the measurement concentrations of glucose are on the high side while containing cholesterol. For example, when the cholesterol concentration is 200mg/dl, the measurement result of glucose with near-infrared spectroscopy will increase 7.961882mg/dl comparing to cholesterol-free glucose solution. Therefore, it is necessary to take steps to reduce cholesterol's effects.

We study the problem of separation of extracellularly recorded spikes by means of an artificial neural network (NN) and its modifications - wavelet neural networks (WNN). Advantages of networks over the standard approaches such as, e.g., the principal component analysis (PCA) are discussed. Application of neural networks seems to be a highly efficient way to improve classification provided by PCA.

We present a non-invasive, label-free imaging technique called Ultrahigh Sensitive Optical Microangiography (UHSOMAG) for high sensitive volumetric imaging of renal microcirculation. The UHS-OMAG imaging system is based on spectral domain optical coherence tomography (SD-OCT), which uses a 47000 A-line scan rate CCD camera to perform an imaging speed of 150 frames per second that takes only ~7 seconds to acquire a 3D image. The technique, capable of measuring slow blood flow down to 4 um/s, is sensitive enough to image capillary networks, such as peritubular capillaries and glomerulus within renal cortex. We show superior performance of UHS-OMAG in providing depthresolved volumetric images of rich renal microcirculation. We monitored the dynamics of renal microvasculature during renal ischemia and reperfusion. Obvious reduction of renal microvascular density due to renal ischemia was visualized and quantitatively analyzed. This technique can be helpful for the assessment of chronic kidney disease (CKD) which relates to abnormal microvasculature.

In the current report an approach of probing a scattering turbid medium with the back-scattered circular polarized light is presented. Circular polarization survives more scattering events than the direction of its propagation, whereas the helicity of backscattered optical radiation depends noticeably on the size of scattering particles. We demonstrate that the helicity flip of circular polarized light can be observed experimentally in the tissue-like media, and that it's sensitive to the direction of light propagation. The flip in helicity is clearly seeing as the polarization vector traverse of the Q-U plane of the Poincaré sphere. It has been also shown that influenced by optical clearing the changes of polarization of scattered laser light can be clearly observed and analyzed quantitatively by tracking the polarization vectors on the Poincaré sphere.

A new type of photonic crystal fibers (PCFs) that can be used as sensitive elements of chemical and biological sensors is presented. Hollow core photonic crystal fibers refer to a type of optical waveguides, showing unique optical properties such as photonic band gap formation and high sensitivity for refraction index, absorption and scattering coefficient of a medium within a hollow core. A significant influence of internal medium scattering coefficient on a PCF's guiding properties becomes basis for design of blood typing automatization technique specifically. Recently obtained experimental results, regarding PCF's sensitivity for internal medium optical properties changing, are presented as well.

Light scattering in blood caused by refractive index mismatch between erythrocyte cytoplasm and blood plasma leads to a reduction in imaging spatial resolution, imaging depth and contrast of optical imaging techniques. A possible solution to this problem is of the addition of biocompatible clearing agents, such as glucose, fructose, glycerol, dextrans etc. The basic principle of the optical clearing technique is refractive index matching between erythrocyte cytoplasm and blood plasma. Optical clearing, a technique that has been successfully demonstrated with biologic tissue, represents a promising approach to increasing the imaging depth for various techniques, for example optical coherence tomography (OCT). OCT is based on low-coherence interferometry to produce cross-sectional tomographic imaging of the internal microstructure in materials and biological tissues by measuring the echo time delay and magnitude of backscattered light. One of the main advantages of this technique is the ability to investigate turbid and highly scattering media, such as whole blood. To determine the optimal concentration of clearing agents required for blood optical clearing in order to improve light penetration depth for optical coherence tomography, clearing agents such as glucose and fructose, with various concentrations were added to blood and investigated by OCT. Changes in light attenuation and sedimentation and aggregation properties of blood depending on particular agent and its concentration were studied.

The results of experimental study of monitoring the microcirculation in tissue superficial layers of the internal organs at gastro-duodenal hemorrhage with the use of laser speckles contrast analysis technique are presented. The microcirculation monitoring was provided in the course of the laparotomy of rat abdominal cavity in the real time. Microscopic hemodynamics was analyzed for small intestine and stomach under different conditions (normal state, provoked ischemia, administration of vasodilative agents such as papaverine, lidocaine). The prospects and problems of internal monitoring of micro-vascular flow in clinical conditions are discussed.

Neural activation generates a hemodynamic response to the localized region replenishing nutrients to the area. Changes in vigilance state have been shown to alter the vascular response where the vascular response is muted during wake compared to quiet sleep. We tested the saturation thresholds of the neurovascular response in the auditory cortex during wake and sleep by chronically implanting rats with an EEG electrode, a light emitting diode (LED, 600 nm), and photodiode to simultaneously measure evoked response potentials (ERPs) and evoked hemodynamic responses. We stimulated the cortex with a single speaker click delivered at random intervals 2-13 s at varied stimulus intensities ranging from 45-80 dB. To further test the potential for activity related saturation, we sleep deprived animals for 2, 4, or 6 hours and recorded evoked responses during the first hour recovery period. With increasing stimulus intensity, integrated ERPs and evoked hemodynamic responses increased; however the hemodynamic response approached saturation limits at a lower stimulus intensity than the ERP. With longer periods of sleep deprivation, the integrated ERPs did not change but evoked hemodynamic responses decreased. There may be physical limits in cortical blood delivery and vascular compliance, and with extended periods of neural activity during wake, vessels may approach these limits.