The reflectance spectra of the human skin in visible and near-infrared (NIR) spectral region have been calculated using the Monte Carlo technique, and the specular and internal reflection on the medium surface is taken into account. Skin is represented as a complex inhomogeneous multi-layered highly scattering and absorbing medium. The model takes into account variations in spatial distribution of blood, index of blood oxygen saturation, volume fraction of water and chromophores content. The simulation of the skin tissues optical properties and skin reflectance spectra are discussed. Comparison of the results of simulation and in vivo experimental results are given.

We investigate the scattering and multiple scattering of a typical laser beam (lambda = 800 nm) in the intermediate scattering regime. The turbid media used in this work are homogeneous solutions of monodisperse polystyrene spheres in distilled water. The two-dimensional distribution of light intensity is recorded experimentally, and calculated via Monte Carlo simulation for both forward and side scattering. The contribution of each scattering order to the total detected light intensity is quantified for a range of different scattering phase functions, optical depths, and detection acceptance angles. The Lorentz-Mie scattering phase function for individual particles is varied by using different sphere diameters (D = 1 and 5 mum). The optical depth of the turbid medium is varied (OD = 2, 5, and 10) by employing different concentrations of polystyrene spheres. Detection angles of theta(a) = 1.5 degrees and 8.5 degrees are considered. A novel approach which realistically models the experimental laser source is employed in this paper, and very good agreement between the experimental and simulated results is demonstrated. The data presented here can be of use to validate any other modern Monte Carlo models which generate spatially resolved light intensity distributions. Finally, an effective correction procedure to the Beer-Lambert law is proposed based on the Monte Carlo calculation of the ballistic photon contribution to the total detected light intensity.

The decomposition of the Mueller matrix of blood films has been carried out using differential matrices with polarized and depolarized parts. The use of a coherent reference wave is applied and the algorithm of digital holographic reconstruction of the field of complex amplitudes is used. On this basis, the 3D Mueller-matrix diffuse tomography method—the reconstruction of distributions of fluctuations of linear and circular birefringence of depolarizing polycrystalline films of human blood is analytically justified and experimentally tested. The dynamics of the change in the magnitude of the statistical moments of the first-fourth order, which characterize layer-by-layer distributions of fluctuations in the phase anisotropy of the blood film, is examined and analyzed. The most sensitive parameters for prostate cancer are the statistical moments of the third and fourth orders, which characterize the asymmetry and kurtosis of fluctuations in the linear and circular birefringence of blood films. The excellent accuracy of differentiation obtained polycrystalline films of blood from healthy donors and patients with cancer patients was achieved.

Thorn CE, Matcher SJ, Meglinski IV, Shore AC. Is mean blood saturation a useful marker of tissue oxygenation?. Am J Physiol Heart Circ Physiol 296: H1289 -H1295, 2009. First published March 13, 2009 doi:10.1152/ajpheart.01192.2008.-Increasingly we are monitoring the distribution of oxygen through the microcirculation using optical techniques such as optical reflectance spectroscopy (ORS) and near-infrared spectroscopy. Mean blood oxygen saturation (SmbO2) and tissue oxygenation index measured by these two techniques, respectively, evoke a concept of the measurement of oxygen delivery to tissue. This study aims to establish whether SmbO2 is an appropriate indicator of tissue oxygenation. Spontaneous fluctuations in SmbO2 observed as changes in concentration of oxyhemoglobin ([HbO2]) and deoxyhemoglobin ([Hb]) were measured by ORS in the skin microcirculation of 30 healthy subjects (15 men, age 21-42 yr). Fourier analysis identified two distinctly different spontaneous falls in SmbO2. The first type of swing, thought to be induced by fluctuations in arterial blood volume, resulted from the effects of respiration, endothelial, sympathetic, and myogenic activity. There was no apparent change in [Hb]. In contrast, a second type of swing resulted from a fall in [HbO2] accompanied by a rise in [Hb] and was only induced by endothelial and sympathetic activity. Thus the same fall in SmbO2 can be induced by two distinct responses. A "type I" swing does not suggest an inadequacy in oxygen delivery whereas a "type II" swing may indicate a change in oxygen delivery from blood to tissue. SmbO2 alone cannot therefore be accepted as a definitive marker of tissue oxygenation.optical reflectance spectroscopy; microcirculation THE EXQUISITE STRUCTURE OF the microcirculation is designed to deliver nutrients to every cell in the human body. The development over the last 30 years of noninvasive optical techniques such as optical reflectance spectroscopy (ORS) (2,18,22,33) and near-infrared spectroscopy (NIRS) (7, 23) has significantly advanced our understanding of the hemodynamics of the cutaneous (1, 20), muscle (36), cerebral (11,13,29,48), and gastrointestinal (15, 38) microcirculation. Furthermore, mean blood saturation (S mb O 2 ) and tissue oxygen index (TOI) derived by ORS and NIRS, respectively, evoke a concept that we can also measure the oxygen delivery to the tissue. These parameters are increasingly being identified as indicators of tissue hypoxia (1,3,8,15,21,28,34,47), which is a common end product of circulatory shock and a primary target for resuscitation efforts (5, 37).The primary goal of this study was to establish whether cutaneous tissue oxygen saturation (i.e., S mb O 2 ) derived by ORS is an appropriate indicator of tissue oxygenation. A further goal was to explore differences in S mb O 2 across cuta- [Hb] across all the vessels of the microcirculation of the skin. Therefore the derived S mb O 2 is a mean blood oxygen saturation across arterioles, capillaries, and venules. METHODS ORS.The ORS instrumentatio...

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High dynamic range optical-to-near-infrared transmission measurements for different parts of human body in the spectral range from 650 to 950 nm have been performed. Experimentally measured spectra are correlated with Monte Carlo simulations using chromaticity coordinates in CIE 1976 L*a*b* color space. Both a qualitative and a quantitative agreement have been found, paving a new way of characterizing human tissues in vivo. The newly developed experimental and computational platform for assessing tissue transmission spectra is anticipated to have a considerable impact on identifying favorable conditions for laser surgery and optical diagnostics, while providing supplementary information about tissue properties.

The ability of noble metal-based nanoparticles (NPs) (Au, Ag) to drastically enhance Raman scattering from molecules placed near metal surface, termed as surface-enhanced Raman scattering (SERS), is widely used for identification of trace amounts of biological materials in biomedical, food safety and security applications. However, conventional NPs synthesized by colloidal chemistry are typically contaminated by nonbiocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. In this article, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and AuSi hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection. We show that these Au-based nanomaterials can efficiently enhance Raman signals from model R6G molecules, while the enhancement factor depends on the content of Au in NP composition. Profiting from the observed enhancement and purity of laser-synthesized nanomaterials, we demonstrate successful identification of 2 types of bacteria (Listeria innocua and Escherichia coli). The obtained results promise less disturbing studies of biological systems based on good biocompatibility of contamination-free laser-synthesized nanomaterials.

Optical clearing is an effective method to reduce light scattering of biological tissues that provides significant enhancement of light penetration into the biological tissues making non-invasive diagnosis more feasible. In current report Optical Coherence Tomography (OCT) in conjunction with optical clearing is applied for assessment of deep cartilage layers and cartilage-bone interface. The solution of Iohexol in water has been used as an optical clearing agent. The cartilage-bone boundary becomes visible after 15 min of optical clearing that enabling non-invasive estimation of its roughness: Sa = 10 ± 1 µm. The results show that for 0.9 mm thick cartilage optical clearing is stopped after 50 min with an increase of refractive index from 1.386 ± 0.008 to 1.510 ± 0.009. Current approach enables more reliable detection of arthroscopically inaccessible regions, including cartilage-bone boundary and subchondral bone, and potentially improves accuracy of the osteoarthritis diagnosis.