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Spectral reflectance in human skin tissue has been studied through Monte Carlo simulation using the Nine-layered skin tissue model. It is important to estimate absorption and scattering parameters of human skin tissue to know the condition of human skin. In this study, we investigated a method for estimating the absorption and scattering parameters by considering the effect of specific layers on the spectral band in the spectral reflectance database of human skin generated by Monte Carlo simulation.

We address the problem of differential diagnostics of chronic spontaneous urticaria and urticarial vasculitis. The clinical pictures of these two allergy diagnoses are similar, however a well-trained pathologist can see the differences in skin tissue on the microscopic level, and thus the histological study of skin biopsy is usually performed to prescribe the right treatment. To increase the throughput and quality of the histological study and differential diagnostics of chronic spontaneous urticaria and urticarial vasculitis, we propose an imaging system with neural-network-based classification of skin tissue structures. The capabilities of a hyperspectral microscopic visualization system with acousto-optical module for increasing the efficiency of neural network training are also being considered.

High-resolution ultrasonic imaging has been increasingly used in dermatology as a complementary technique for cutaneous lesions assessment. The clinical application of ultra-high frequency ultrasound can reduce the number of invasive procedures, such as biopsies, and assist in surgical planning. The success of ultrasonic methods depends on the ability of modern imaging systems to deliver reliable and interpretable information. We present a new handheld high-resolution ultrasonic imager designed for dermatological use. The device operates at 50-100 MHz and provides B-scan images with up to 4 mm penetration depth and 40μm axial resolution. Adaptive signal processing algorithms allow highlighting anatomical and pathological features of the skin tissue. The primary skin layers, as well as the skin appendages, are clearly detectable on the obtained acoustical images. High-resolution characterization of skin morphology allows assessing the overall condition of the skin and can be used for diagnostic purposes. The new device will be useful for the number of dermatological applications: surgery planning and image-guided intervention, assessment of wound healing and skin grafts, vascular anomalies, inflammatory diseases, and numerous cosmetic complications.

Cutaneous malignant melanoma is the deadliest and most aggressive form of skin cancer and is fatal if left untreated. Currently, the most commonly used technique to detect melanoma relies on a purely subjective test termed the asymmetry, border, core, diameter, and evolution (ABCDE) test, which is performed visually by dermatologists or other medical professionals. The ABCDE method is at best a qualitative guideline, the success of which depends strongly on the skill and experience of the practitioner. The dermascope is the primary instrument for identification of skin cancer; however, successful results using dermoscopy also require skilled practitioners for accurate diagnosis. Therefore, a significant need exists to identify the presence of melanoma using non-invasive methods that do not require specialized training or skill. To meet this need, we are investigating a biomimetic, non-spectroscopic infrared (IR) optical approach for detection of skin cancer. The biomimetic approach, inspired by human color vision, only requires three broadband optical filters in the mid-infrared (2 – 8 μm), to classify tissue as cancerous or non-cancerous. We present preliminary results demonstrating the ability of this approach to discriminate between cancerous and non-cancerous skin tissue. The biomimetic approach outlined in this paper has the potential to lead to the development of small, inexpensive, portable sensors for various medical applications such as skin cancer diagnosis. Such sensors would require minimal or no training, and could be widely deployed in areas with less access to specialized care.

Fluorescence lifetime imaging (FLIM) can reveal information about the spatial distribution of a fluorescent molecule together with information about its microenvironment, which makes FLIM find wide applications in biomedical research. In this paper, we implemented time-correlated single-photon counting-based fluorescence lifetime imaging microscopy (TCSPC-based FLIM) in skin cancer diagnosis, including malignant melanoma (MM), squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). The fluorescence lifetime images and two-dimensional vector analysis of normal and several cancerous skin tissue sections stained with hematoxylin-eosin (H&E) were mapped and the results showed that cancerous skin tissue has a relatively shorter fluorescence lifetime compared with normal skin tissue. Moreover, the fluorescence lifetime of skin cancer tissue sections with different clinical stages was measured, and the quantitative relationship between fluorescence lifetime and pathological stage of skin cancer was explored.

Mueller polarimetry imaging is gaining acceptance in diagnostic imaging as a potential tool for identifying tissue pathology by the integrated analysis of tissue response to polarized light. The Mueller matrix derived parameters have been related to the structural changes occurring in the tissues during pathogenesis of a disease. An in-house developed Mueller polarimetric imaging system has been explored in this study to differentiate between the normal and sclerodermic regions of unstained skin biopsy samples with varying collagen densities in the dermis. The optical response of excessive collagen deposition in scleroderma gets reflected in the depolarization, diattenuation, and retardance parameters obtained through polar decomposition and singular value analysis. In this study, higher depolarization, retardance and diattenuation values were observed in the scleroderma region as compared to their normal counterpart, suggesting an increased level of collagen deposition, which was further correlated with the histopathological findings. The developed system aims at its deployment in pathology labs to provide stain-free examination procedures in the long run.

The changes in the oxy- and deoxygenated hemoglobins at different depths of skin tissue were obtained from the diffuse reflectance spectra in three wavelength ranges of the skin. The influence of the optical path length in the calculation on the results of the hemoglobin change was evaluated.

To measure optically physiological condition inside skin tissue, it is important to estimate optical parameters in skin tissue. In this study, we investigated a method to estimate absorption and scattering parameters in skin tissue from the spectral reflectance database constructed by using Monte Carlo simulation with a nine-layered skin tissue model.

We have developed so far the method for imaging simultaneously blood flow and blood concentration change in skin tissue by using two-wavelength near infrared laser speckle patterns. We conducted experiments for human volunteers to confirm the feasibility of the method for estimating temporal response in the blood flow and blood concentration change in a human finger to occlusion on a human arm with different pressures from 50 to 150 mmHg. The results demonstrated that the response may depend on individual minimum and maximum blood pressure values.

Human skin surface has unevennesses called sulcus cutis and crista cutis. It is known that these affect the light propagation in human skin. In this study, we made a prototype of skin tissue phantom and investigated its spectral properties and problems to be solved.

Light propagation into human skin tissue is studied by using Monte Carlo simulation (MCS) with the multi-layered skin tissue model. In this study, we analyzed light propagation in various internal conditions of skin tissue by calculating photon fluence based on Monte Carlo simulation. And we examined a method for quantitative evaluation on the depth and spread of light propagation in skin tissue.

There are sulcus cutis and crista cutis on human skin surface. It is known that these affect the light propagation in human skin. To investigate it experimentally, it is desirable to reproduce sulcus cutis and crista cutis in skin tissue phantom. In this study, we made a prototype of skin tissue phantom having a shape of sulcus cutis and crista cutis, and investigated its optical properties and problems to be solved.

Diffuse reflectance spectroscopy offers a noninvasive, fast, and low-cost alternative to visual screening and biopsy for skin cancer diagnosis. We have previously acquired reflectance spectra from 137 lesions in 76 patients and determined the capability of spectral diagnosis using principal component analysis (PCA). However, it is not well elucidated why spectral analysis enables tissue classification. To provide the physiological basis, we used the Monte Carlo look-up table (MCLUT) model to extract physiological parameters from those clinical data. The MCLUT model results in the following physiological parameters: oxygen saturation, hemoglobin concentration, melanin concentration, vessel radius, and scattering parameters. Physiological parameters show that cancerous skin tissue has lower scattering and larger vessel radii, compared to normal tissue. These results demonstrate the potential of diffuse reflectance spectroscopy for detection of early precancerous changes in tissue. In the future, a diagnostic algorithm that combines these physiological parameters could be enable non-invasive diagnosis of skin cancer.

Evidence based medicine aims to provide a quantifiable framework to support cancer optimal treatment selection. Pathological examination is the main evidence used in medical management, yet the level of quantification is low and highly dependent on the examiner expertise. This paper presents and evaluates a method to extract graph based topological features from skin tissue images to identify cancerous regions associated to basal cell carcinoma. The graph features constitute a quantitative measure of the architectural tissue organization. Results show that graph topological features extracted from a nuclei based distance graph, particularly those related to local density, have a high predictive value in the automated detection of basal cell carcinoma. The method was evaluated using a leave-one-out validation scheme in a set of 9 skin Whole Slide Images obtaining a 0.76 F-score in distinguishing basal cell carcinoma regions in skin tissue whole slide images.

Results of hyperspectral imaging analysis for in vivo visualization of skin neoplasms are presented. 16 melanomas, 19 basal cell carcinomas and 10 benign tumors with different stages of neoplasm growth were tested. The HSI system provide skin tissue images with 5 nm spectral resolution in the range of 450-750 nm with automatic stabilization of each frame compensating displacement of the scanning area due to spontaneous macro-movements of the patient. The integrated optical densities in 530-600 and 600-670 nm ranges are used for real-time hemoglobin and melanin distribution imaging in skin tissue. It was shown that the total accuracy of skin cancer identification exceeds 90% and 70% for differentiation of melanomas from BCC and begihn tumors. It was demonstrated the possibility for HSI classification of melanomas of different stages.

Melanoma skin cancer has one of the highest mortality rates of all types of cancer if not detected at an early stage. The survival rate is highly dependent on its penetration depth, which is commonly determined by histopathology. In this work, we aim at combining optical coherence tomography and optoacoustic as a non-invasive all-optical method to measure the penetration depth of melanoma. We present our recent achievements to setup a handheld multimodal device and also results from first in vivo measurements on healthy and cancerous skin tissue, which are compared to measurements obtained by ultrasound and histopathology. © 2016 SPIE.

Optical properties of the biological tissue play an important role to a correct use of optical techniques for therapy and diagnosis. The mice skin presents morphological differences due to characteristics such as gender, body mass and age. Murine models are frequently used in pre-clinical trials in optical therapy and diagnosis. Therefore, the assessment of the skin tissue in animal models is needed for a proper understanding of how light interacts with skin. Noninvasive techniques such as optical coherence tomography (OCT) have been used to obtain optical information of the tissue, as the attenuation coefficient, with the advantage of obtaining sectional images in real time. In this study, eight female BALB/c albino mice (twenty-four weeks old) and eight male C57BL/6 black mice (eight weeks old) were used to measure the attenuation coefficient of the light in the skin, utilizing the OCT technique, aiming to check for influence of the aging process. Two moments were assessed twenty-two weeks apart from each other. Our data show that the aging process significantly affects the light attenuation coefficient in mice skin. Twenty-two weeks after, statistical significant differences were observed between groups within a same strain. We conclude that light attenuation coefficient of mice skin may be influenced by factors such as disorganization of the dermis. Morphological aspects of skin should be taken into account in studies that involve optical strategies in murine models.

Fluorescent spectroscopy (FS) is becoming more widely used in chemistry, biology, in various fields of medical technology and medicine in general. Many purulent wounds, burns and other destructive inflammatory processes are accompanied by changes in the fluorescent activity of the tissues, which occurs due to a misbalance in accumulation of natural fluorophores: FAD, NADH, lipofuscin, porphyrins, structural proteins, etc. The study of redox ratio (RR), characterizing the metabolic processes, is important in the assessment of the metabolic activity ofmicrocirculatory-tissue systems (MTS). However, one of the big problems of the FS method is still the correct interpretation of the data and the development of practical methods for its application in clinical medicine. To solve this problem and create new diagnostic criteria, we propose to evaluate the adaptive capacity of MTS using indicators of links between nutritive blood flow and redox ratio during a physiological rest and functional load (occlusion test). As is known, these parameters (RR and nutritive blood flow) characterize the metabolic activity of tissues.We have performedan experimental study of the relationship between the RR, defined by FS, and nutritive blood flow, defined by the methods of laser Doppler flowmetry. Preliminary results in the study of a complex approach to diagnosis of the state of biological tissue were obtained. A positive relationship between the nutritive blood flow in the microcirculatory channel and RR of skin tissue is observed.The speed of change of metabolism in the phase of occlusion and reperfusion and duration of phase of recovery may be the criteria for adaptive capabilities of MTS, which has practical significance for physiology and medicine.

We present new near-infrared (NIR) imaging technique for analyzing the moisturizer drop dynamics on the human skin surface. From the measurement experiment for the vertical water content in the skin tissue and light transport simulation, it was clarified that imaging the skin tissue using 1950 nm band effectively visualizes the water distribution. We demonstrate the NIR imaging experiment using originally developed NIR microscopic water imaging system. The relationship between the moisturizer drop dynamics and the water condition of the skin tissue is also discussed.

We report on a method for analysing multispectral images of skin in vivo for the measurement and visualisationof skin characteristics. Four di erent indices were used to characterise skin tissue oxygenation, erythema, totalhaemoglobin and melanin content. Index values were calculated pixel-wise and combined to create index maps tovisualise skin properties. Quantitative measurement of tissue oxygenation saturation was possible by calibratingthe oxygenation index using a commercial, calibrated oximeter. Index maps were tested by arterial occlusionof the index nger with multispectral images taken before, during and after occlusion in a pilot study with 10healthy controls.Keywords: Multispectral imaging, chromophore, tissue oxygenation, erythema, haemoglobin, melanin. 1. INTRODUCTION Multispectral imaging is an established technique that has been applied to many areas of industry and research,including medical application, which is of interest here. Due to its non-invasive nature and low cost applica-tion, hyper- and multi-spectral imaging techniques are being used clinically for skin measurement such as theassessment of burns

Imaging of the skin to detect the signs of cancer becomes very common these days. A new noninvasive skin imaging method developed recently gives an informative image data about the skin tissue by collecting scattered polarized light reflected from a mole area. This method scans the polarization states by continuously rotating a linearly polarized light incident on the lesion and collecting the reflected sequence of images with a CCD camera. The two main wavelengths that were used in the study were 520nm (penetration is about 100μm) and 700nm (penetration is about 200μm). Methods developed in the past to diagnose suspicious moles were implemented to visual images. However, such methods cannot be employed directly to our images because of their different properties. In this paper, we analyze skin moles obtained from this system for the purpose of distinguishing cancerous from benign moles. First, we pre-process the mole image by de-noising, contrast enhancement and intensity-based segmentation of the mole region. Then, an automatic examination of the polarized images is carried out according to characteristics such as their symmetry, cross-image local contrasts and large-scale homogeneity.

Near-infrared spectroscopy(NIRs) is an ideal measurement method for noninvasive blood glucose sensing. In that measuring process, the light propagation path in skin tissue would affect the final near-infrared spectrum greatly. In this talk, the Monte Carlo simulation has been conducted to investigate the effect of dermal thickness variances on blood glucose sensing results at earlobe site. Results demonstrate that the floating reference point exists in the finite five-layered thickness skin model, and the variation of floating reference point under the dermal thickness change is simulated. It is indicated that in the dermal thickness increasing process, there is a rising trend of the floating reference point at each wavelength. It will lay a solid foundation for the further design of an advanced blood glucose detection probe to facilitate the application of NIRs to noninvasive blood glucose sensing eventually.

We have developed a stochastic photon transport model in multilayer skin tissue in an effort to study normal and bruised skins. The model uses a detailed seven layer skin approximation allowing more biologically relevant input than previous models using one or three layers. Our model is improved with clinically obtained reactance spectra in an effort to develop time correlations of chromophore concentrations in developing bruises. This combination of modeling and spectroscopic measurements provides a new tool for detailed, non-invasive studies of human skin tissue.

Nonlinear optical imaging techniques based e.g. on coherent anti-Stokes Raman scattering (CARS) or second-harmonic generation (SHG) show great potential for in-vivo investigations of tissue. While the microspectroscopic imaging tools are established, automized data evaluation, i.e. image pattern recognition and automized image classification, of nonlinear optical images still bares great possibilities for future developments towards an objective clinical diagnosis. This contribution details the capability of nonlinear microscopy for both 3D visualization of human tissues and automated discrimination between healthy and diseased patterns using ex-vivo human skin samples. By means of CARS image alignment we show how to obtain a quasi-3D model of a skin biopsy, which allows us to trace the tissue structure in different projections. Furthermore, the potential of automated pattern and organization recognition to distinguish between healthy and keloidal skin tissue is discussed. A first classification algorithm employs the intrinsic geometrical features of collagen, which can be efficiently visualized by SHG microscopy. The shape of the collagen pattern allows conclusions about the physiological state of the skin, as the typical wavy collagen structure of healthy skin is disturbed e.g. in keloid formation. Based on the different collagen patterns a quantitative score characterizing the collagen waviness - and hence reflecting the physiological state of the tissue - is obtained. Further, two additional scoring methods for collagen organization, respectively based on a statistical analysis of the mutual organization of fibers and on FFT, are presented.

We demonstrate micron-class-resolution frequency-domain OCT at high acquisition-speeds using a commercial supercontinuum source (i.e. 300nm bandwidth centered at 800nm) and a broadband custom astigmatism-corrected spectrometer (i.e. < 0.1 nm spectral resolution over 400nm bandwidth). We achieved 1.3 μm axial resolution in, in vivo skin tissue, with an acquisition speed of 23 A-scans per sec using the implemented FD-OCT.

Skin penetration studies are an important part for the development of dermal drug carrier systems. As a novel approach a 7-tesla Magnetic Resonance Imaging (MRI) Scanner was used to obtain information about the penetration of agents into the skin. The main advantage of this method is, that the properties of the skin does not influence the signals. Compared to optical assessments the MRI method is not limited to imaging depth. Furthermore, it is possible to analyze fat and water components of the skin separately. The aim of this work was to evaluate, if this method is a promising analysis tool for the visualization of the transport of substances across the skin. Gadobutrol (Gadovist®1.0), respresenting a coventional contrast agent in MRI, was used as a model drug for the visualization of the skin penetration. These first promising results showed that Gadobutrol, incorporated in an oil-in-water emulsion, could be detected across the skin tissue compared to an aqueous solution. After 24 hours, the pixel intensity value was increased about 4-fold compared to an untreated tissue.

Engineered skin tissues are widely used in dermatological, pharmacological and toxicological studies and as autologous transplants in wound healing. Due to the high demand for artificial skin equivalents, there is a need for an automation of the manual production process to achieve a high-grade product. Thus, non-invasive monitoring of engineered tissue during the growth cycles is of major significance to understand and consequently improve the growth characteristics of in vitro tissue. Prior to the framework of the automation of artificial humanoid 3d-skin tissue engineering, optimal growth parameters need to be determined. The successful engineering of humanoid tissue is strongly coupled to the composition and structure of the upper epidermal and dermal skin layers. The layers are based on primary humanoid keratinocytes and a collagen - fibroblasts matrix. We applied optical coherence tomography as tissue imaging technology, which offers great potential to detect and characterize the differentiation processes of engineered skin. OCT provides a high resolution in the micron range with an imaging depth of about 1.5mm in semitransparent tissue. Due to a high quality signal to noise ratio, even small changes in signal at the boundary of the skin layers are detectable. In a study, OCT tomograms were taken after each production step of the skin equivalents and compared to the images of histologies.

We propose a method for imaging simultaneously blood flow and hemoglobin concentration change in skin tissue using speckle patterns acquired at two wavelengths of 780 and 830 nm. Experimental results demonstrate that the method is useful for time-varying analysis of blood circulation in human forearm skin tissue from one set of sequential speckle images.

A practical limitation encountered in alcohol research is the relatively small number of body compartments (e.g. blood, liver, tissue) that can be directly interrogated. In this work, an NIR spectroscopic device was investigated that provided a direct measurement of alcohol concentration in skin tissue (interstitial fluid). This work is intended to characterize the relationship of forearm interstitial fluid alcohol concentration relative to capillary blood using a first order kinetic model. Concurrent blood and tissue alcohol concentrations were collected on 101 test subjects while consuming alcohol. Estimates of the first order kinetic rate constant were calculated for each of the subjects. It is hoped that this characterization will lead to further improvements in optical based alcohol monitors for impairment detection.

Numerous publications have qualitatively indicated that the optical clearing technique by using biocompatible hyperosmotic agents could reduce the scattering effects within bio-tissue and further enhance the light to penetrate into it. However, few investigations have been carried out to quantitatively describe this effect and put it in use. In this talk, the permeation courses of biocompatible hyperosmotic agents into porcine skin tissue were simplified. A skin diffusion optical model was built to dynamically describe the courses of biocompatible hyperosmotic agents penetrating into skin, which was affected by the osmotic diffusivity of the model, and the changes of skin optical properties during the permeation courses. Meanwhile, experiments and skin Monte Carlo(MC) simulation studies were performed to investigate the optical clearing of porcine skin tissues medicated without and with biocompatible hyperosmotic agents. Both experimental and MC simulation results showed the availability of the diffusion model, which could quantitatively describe the change degree of optical property parameters with hyperosmotic agents immersing into different layers of skin. Therefore, the skin optical diffusion model would be potentially used to investigate how to quantitatively control the change of the optical property parameters of skin tissue topically applied with biocompatible hyperosmotic agents.

Dimethyl sulfoxside (DMSO) has been used as enhancer for tissue optical clearing technique. However, due to its potential toxicity and possible side effects, taking clearing effects and clinical availability into accounts, a new enhancer will be needed in order to facilitate practical application of tissue optical clearing technique to non-invasive light-based diagnostic and imaging technique. In this talk, it is our aim to introduce a new skin penetration promoter, thiazone, used in the fields of pharmaceutic industry, cosmetic, etc and investigate its availability as a new enhancer for tissue optical clearing technique. Firstly, we analyzed its structure, physical and chemical properties. And then we performed experimental investigation of the effect of DMSO and thiazone as enhancers mixed with polyethylene glycol (PEG) respectively on optical clearing of porcine skin tissue in vitro. Results of direct observation from camera reveal that thiazone has a higher penetration enhancing effect when compared with DMSO as an enhancer when porcine skin was topically impregnated by different mixed-solutions. Optical property parameters, obtained by using double integrating-spheres system and Inverse Adding-Doubling (IAD) method, showed that thiazone led to almost similar reduction in scattering to DMSO did during the same time period. Therefore, in terms of optical application and clinical safety, thiazone could be a better choice than DMSO as an enhancer for optical clearing of skin tissue.

The engineering of human tissue represents a major technique in clinical medicine. Material evaluation of skin is important as preventive medicine. Decubitus originates in pressure and the rub. However, shearing in the skin has exerted the influences on the sore pressures most. This paper examines one demand of crucial importance, namely the real time in vivo monitoring of the shearing characteristics skin tissue. Rheometer is a technology developed to measure viscoelasticity of solid and liquid. To measure viscoelasticity of the skin in the noninvasive with this device, we remodeled it. It is ideal for the continuous monitoring of tissues in vivo.

Based on the analysis of skin morphological structure, the mechanism of cutaneous fluorescence emission and diffuse reflectance formation, a six-layer skin optical model was developed, allowing the variation of blood content in both the upper blood plexus and the deep blood plexus. Monte Carlo simulation was performed to examine the effect of varying tissue blood contents on skin fluorescence and diffuse reflectance spectra. The results demonstrated that (1) Both fluorescence and reflectance spectrum can reflect changes of blood content in skin tissue; (2) The impact of blood content in the upper blood plexus on skin spectra intensity is far larger than that in the deep blood plexus, though there is far less blood in the upper blood plexus; (3) Fluorescence and reflectance spectrum could be used to detect or analyze changes of blood content in skin tissue, especially for treatment monitoring and for evaluating the severity of skin diseases that involving the blood plexus or blood pathological changes in the upper dermis.

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.

It is critical to improve the diffuse reflecting light energy for monitoring the blood glucose level from the skin spectra. The optic fiber probe used in non-invasive detection of blood glucose is consisted of one central fiber around with several optic fibers arranged in circle. The distance between central fiber and circle fibers d and the incidence angle β of the central fiber mainly determine the diffuse reflecting light energy. A three-layered skin model and Monte Carlo simulation algorithm are described to simulate the light propagation and distribution in the skin tissue. Simulation results show d should be greater than 0.05cm and less than 0.1cm, and β should be less than 18°. The simulation results can be used in the probe design.

Recent developments in optical clearing of biological tissue have shown a great promise in enhancing the capabilities of non-invasive light-based diagnostic and imaging techniques due to the increased light penetration into tissue. This study investigates the synergistic effect of hyperosmotic agents of dimethyl sulfoxide (DMSO) and glycerol solutions on optical clearing of skin in vitro. Experimental results from near infrared spectroscopy, direct imaging assessment and mass loss measurement showed that the mixed solutions of DMSO and glycerol caused better clearing effects than that of any single solution alone. In addition, the different clearing effects were observed when skin tissue was treated by different volume-mixing of DMSO and glycerol solutions. The results presented revealed that the DMSO is responsible for the synergistic effect on optical clearing due to its carrier effect and strong penetration capability.

Currently, tissue optical clearing technique has shown a great potential in enhancing the capabilities of non-invasive light-based diagnostic and imaging techniques due to the increased light penetration into tissue. In order to facilitate the clinical availability of tissue optical clearing technique by the use of hyperosmotic agents, this study introduces oleic acid, a mono-unsaturated fatty acid which is generally believed to be safe, as enhancer and investigates the synergistic effect of oleic acid and propylene glycol (PG) on optical clearing of skin tissue in vitro. Experimental results from near infrared spectroscopy, mass loss measurement and transdermal skin resistance (TSR) assessment showed that, compared with dimethyl sulfoxide (DMSO) as enhancer, oleic acid obtained the similar clearing effect. However, due to its potential toxicity, DMSO has been controversial in clinical application. Therefore, in terms of optical application and clinic safety, the results presented revealed that oleic acid could be an optimum choice as enhancer for optical clearing of skin tissue.

Currently, one of the current limitations of Optical Coherence Tomography (OCT) is its penetration depth and imaging contrast because of the fact that the complex morphological nature of biological tissue, especially skin tissue. In this work, we investigate the synergistic effect of oleic acid and propylene glycol on optical clearing of skin tissue in vitro , improve OCT imaging contrast and penetration depth. The results demonstrate the optical clearing effect after topical application of the hyperosmotic agents of PG80 (80% propylene glycol) and OA PG80 (0.1 M oleic acid in 80% propylene glycol), which enhances not only the depth-imaging capability, but also the imaging contrast of optical coherence tomography. It should be noticed that OA PG80 obtained the better effect in a shorter time than PG80 alone. Therefore, in terms of optical application and clinical safety, OA PG80 could be better choice to improve penetration depth and imaging contrast of OCT technique.

This paper describes a new biometric technology based on the optical properties of skin. The new technology can perform both identity verification and sample authenticity based on the optical properties of human skin. When multiple wavelengths of light are used to illuminate skin, the resulting spectrum of the diffusely reflected light represents a complex interaction between the structural and chemical properties of the skin tissue. Research has shown that these spectral characteristics are distinct traits of human skin as compared to other materials. Furthermore, there are also distinct spectral differences from person to person. Personnel at Lumidigm have developed a small and rugged spectral sensor using solid-state optical components operating in the visible and very near infrared spectral region (400-940nm) that accurately measures diffusely reflected skin spectra. The sensors are used for both biometric determinations of identity as well as the determination of sample authenticity. This paper will discuss both applications of the technology with emphasis on the use of optical spectra to assure sample authenticity.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The study of Methylene Blue penetration in both skin and subcutaneous fat is presented. Experiments have been carried out with both rat skin and human adipose tissue in vitro at room temperature. Microscopic analysis with digital imaging system has been applied for visualizing and investigation of the Methylene Blue diffusion in the epidermal, dermal and adipose tissue. Diffusion coefficient of Methylene Blue in skin in vitro has been estimated.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

There are two events happening simultaneously after the impregnation of tissue with the hyperosmotic agents. The diffusion of the agents into tissue reduces the refractive index mismatch between the scattering centres and background medium. And in the meantime, the hyperosmotic characteristics of agents cause tissue dehydration. Both processes are believed to have the effects on reducing light scattering of biological tissue. In order to investigate the role of dehydration in optical clearing effect on the tissue with the application of hyperosmotic agents, the skin tissues with the application of glycerol are dynamically imaged with optical coherence tomography (OCT). We demonstrate experimentally that both the depth and the contrast of OCT imaging of tissue can be enhanced by the application of agents. Higher concentration of agents causes more water loss of skin tissue and a stronger optical clearing effect. We suggest that the dehydration induced by the agents contributes to the enhancement of both OCT imaging depth and contrast. OCT imaging movies of optical clearing effect of hyperosmotic agents on the skin tissues in vitro are provided.

To estimate the melanin and hemoglobin concentrations in the human skin tissue, we propose a method of using the multiple regression analysis combined with the Monte Carlo technique for spectral reflectance from the skin surface. In the method, the Monte Carlo simulation was used to prepare data sets of various concentrations and absorbance spectra for determination of conversion coefficients from the absorbance to the concentration in the regression analysis. Numerical simulation was conducted for a two-layered skin tissue model to verify the usefulness of the present method.

We previously reported that for rat burn models, deep dermal burns and deep burns can be well differentiated by measuring the propagation time of the photoacoustic signals originated from the blood in the healthy skin tissue under the damaged tissue layer. However, the diagnosis was based on point measurement in the wound, and therefore site-dependent information on the injuries was not obtained; such information is very important for diagnosis of extended burns. In the present study, we scanned a photoacoustic detector on the wound and constructed two-dimensional (2-D) images of the blood-originated photoacoustic signals for superficial dermal burns (SDB), deep dermal burns (DDB), deep burns (DB), and healthy skins (control) in rats. For each burn model, site-dependent variation of the signal was observed; the variation probably reflects the distribution of blood vessels in the skin tissue. In spite of the variation, clear differentiation was obtained between SDB, DDB, and DB from the 2D images. The images were constructed as a function of post burn time. Temporal signal variation will be also presented.

We present experimental results on study of Methylene Blue penetration into skin using a method of digital analysis of color images. Experiments were carried out with a rat skin in vitro. Dependence of the penetration depth of Methylene Blue on dyeing time ofthe tissue was researched. Diffusion coefficients of Methylene Blue within the skin in vitro were estimated.

Non-invasive blood glucose monitoring has long been proposed as a means for advancing the management of diabetes through increased measurement and control. The use of a near-infrared, NIR, spectroscopy based methodology for noninvasive monitoring has been pursued by a number of groups. The accuracy of the NIR measurement technology is limited by challenges related to the instrumentation, the heterogeneity and time-variant nature of skin tissue, and the complexity of the calibration methodology. In this work, we discuss results from a clinical study that targeted the evaluation of individual calibrations for each subject based on a series of controlled calibration visits. While the customization of the calibrations to individuals was intended to reduce model complexity, the extensive requirements for each individual set of calibration data were difficult to achieve and required several days of measurement. Through the careful selection of a small subset of data from all samples collected on the 138 study participants in a previous study, we have developed a methodology for applying a single standard calibration to multiple persons. The standard calibrations have been applied to a plurality of individuals and shown to be persistent over periods greater than 24 weeks.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In recent years the interest in the determination of optical properties of layered tissue structure has resurfaced. Applications include, for example, studies on layered skin tissue and underlying muscles, imaging of the brain underneath layers of skin, skull, and meninges, and imaging of the fetal head in utero beneath the layered structures of the maternal abdomen. In this work we approach the problem of layered structures in the framework of model-based iterative image reconstruction schemes. These schemes are currently developed to determine the optical properties inside tissue from measurement on the surface. If applied to layered structure these techniques yield substantial improvements over currently available semi-analytical approaches.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Experimental results on in vivo and in vitro immersion clearing dynamics of the skin under action of the osmotic agent are presented. The significant decrease of the human skin reflectance in vivo under action of glucose solution is demonstrated. In vitro experiments with dyed immersion agents have shown that the immersion mostly penetrates into skin tissue though the dermal layer. Diffusion of the immersion agent through the stratum corneum barrier was insignificant. It was shown the hypodermic injection of the immersion agent is an effective way for the agent administration. The time-dependent contrast of the blood perfused areas in the cleared skin was estimated. The diffusion coefficient of 40%-glucose solution in skin in vivo was estimated as D equals (2.56+/- 0.13)(DOT)10-6cm2sec.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The bluish appearance of veins in the skin tissue was experimentally investigated by in vivo and in vitro measurements. The color of skin surface including veins inside was evaluated by spectrophotometry and color analysis in the CIEXYZ and CIELAB colorimetric systems. The bluish appearance was successfully interpreted by the dominant wavelength and the color difference. Results for in vitro experiments showed that the degree of bluish appearance depends on the depth and diameter of blood vessels.

Because of the melanin, hemoglobin and water molecules, etc. contained, light absorption of human skin tissue changes with wavelength of light. This is the principle used in laser cosmetology for treating pigment diseases and vascular lesion diseases as well as skin decoration such as body tattooing, eyebrow tattooing, etc. The parameters of treatment used in laser cosmetology principally come from the research of the skin tissue optical characteristics of whites, and it is not suitable for the Oriental. The absorption spectrum of yellow race alive skin has been researched. The detecting platform for use in the measuring of vivi-tissue absorption spectrum has been developed which using opto-electronic nondestructive testing and virtual instrument techniques. The degree of pathological changes of skin can be detected by this platform also, thus the shortcoming of dosage selection in laser clinical treatments which have been decided only by naked eye observation and past experience of doctors can be solved.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.