ASSESSMENT OF RAT BRAIN MORPHOFUNCTIONAL STATE IN A PARKINSON'S MODEL: INFLUENCE OF THERAPEUTIC AGENTS OF ANIMAL AND SYNTHETIC ORIGINS.

In neurodegenerative diseases, particularly in Parkinson's disease (PD), antinociceptive centers are often implicated in neurodegeneration, leading to persistent pain unresponsive to narcotic substances. This study investigated the periaqueductal gray matter (PAG) and the nucleus raphe magnus (NRM), components of the brain's antinociceptive system. In conditions of rotenone intoxication (an experimental PD model), morphological changes in intracellular structures were observed in PAG and NRM neurons, indicating metabolic disorders characteristic of PD (alterations in the shape and size of neuronal bodies and processes, disruption of acid phosphatase activity in neuron cytoplasm). Under the influence of bacterial melanin and in combination with synoestrol, positive changes in structural properties were observed in PAG and NRM neurons compared to the rotenone model of PD. This included the preservation of the morphological characteristics typical of these brain regions, with cells exhibiting shapes and sizes close to normal. Furthermore, under the influence of these therapeutic agents, an increase in phosphatase activity in cell cytoplasm was detected, indicating an acceleration of metabolic processes (metabolic activation) disrupted by rotenone intoxication. The data obtained suggests that bacterial melanin and synoestrol may act as potential neuroprotective agents against PAG and NRM neurons in the rat brain in the rotenone model of PD. Further research is needed to elucidate the mechanisms of action of therapeutic doses and propose their use in the treatment of PD, either in isolation or combination therapy.

Can skin histology be a useful tool for ancestry assessment in forensic settings? Ancestry assessment based on melanin pigment.

Building the biological profile of a deceased person represents a pivotal step in order to achieve the victim's identification. Specifically with regard to ancestry, the melanin distribution pattern in the dermal-epidermal layers has been poorly explored in the forensic field as a potential useful tool. In particular, nothing has been reported about the reliability of such method in bodies in active decay or in advanced state of decomposition. In this study fragments of skin sampled from bodies of known ancestry, both in good and in poor states of preservation, were subjected to histological analysis. We selected 15 subjects, which were divided into three groups: group A (5 white Europeans), group B (5 black Africans) and group C (5 Orientals). A double skin sample was performed on all the bodies, one from the abdomen and the other one from the right forearm. After histological processing and staining with hematoxylin and eosin (H&E) and Masson-Hamperl trichrome technique, the cutaneous melanin distribution pattern was assessed using a semi-quantitative score. The melanin distribution patterns observed both in fresh and in putrefied cadaveric skin were found to be in all cases consistent with the victims' known ancestry. Moreover no differences were observed between abdominal and forearm skin samples and all the histological findings highlighted by H&E were confirmed by the Masson-Hamperl trichrome staining. We demonstrated that the histological analysis aimed at assessing the melanin distribution pattern may be a valuable useful tool in the assessment of ancestry.

Assessment and grading of pigmentation in chronic venous insufficiency.

INTRODUCTION: Chronic venous insufficiency causes skin pigmentation of the leg ranging from small patches of mild dyschromia to extensive areas of severe skin pigmentation. It is thought that the pigmentation is mainly due to haemosiderin or melanin deposition. Erythrodiapedesis which occurs as a result of venular hypertension causes erythrocytes to migrate across the microvascular network into the dermis. METHODS: We categorized the grading of pigmentation into four grades: +, few spots; ++, pigmentation over gaiter area; +++, pigmentation involving leg and ankle; ++++, heavily pigmented (dark). Skin biopsies were taken from the patient while undergoing surgery; two biopsies were taken from each patient, one from apparently normal skin and other from the site of pigmentation. A total of 45 patients diagnosed as chronic venous insufficiency with pigmentation were included in the study and five patients included in control. The biopsy specimens were sent to pathology department for H&E, Perls stain and IHC for S100. RESULTS: Majority of cases, i.e. 62% of limbs fall under (++) grade of pigmentation, followed by (+) grade of pigmentation in 20%, while (+++) and (++++) constitute 9% of the cases each. Increased melanin deposition was seen in 40 pigmented skin biopsies and 3 normal skin biopsies from the case group, and normal melanin deposition was seen in all the non-varicose controls. CONCLUSION: We have tried to categorize pigmentation in chronic venous insufficiency into four grades. As the grade of pigmentation increases the per cent of cases with ulceration is increasing. It was observed that presence of melanin deposition irrespective of the grade of pigmentation was distributed more towards the advanced clinical classification (C5 and C6).

Method using in vivo quantitative spectroscopy to guide design and optimization of low-cost, compact clinical imaging devices: emulation and evaluation of multispectral imaging systems.

With recent proliferation in compact and/or low-cost clinical multispectral imaging approaches and commercially available components, questions remain whether they adequately capture the requisite spectral content of their applications. We present a method to emulate the spectral range and resolution of a variety of multispectral imagers, based on in-vivo data acquired from spatial frequency domain spectroscopy (SFDS). This approach simulates spectral responses over 400 to 1100 nm. Comparing emulated data with full SFDS spectra of in-vivo tissue affords the opportunity to evaluate whether the sparse spectral content of these imagers can (1) account for all sources of optical contrast present (completeness) and (2) robustly separate and quantify sources of optical contrast (crosstalk). We validate the approach over a range of tissue-simulating phantoms, comparing the SFDS-based emulated spectra against measurements from an independently characterized multispectral imager. Emulated results match the imager across all phantoms (<3 % absorption, <1 % reduced scattering). In-vivo test cases (burn wounds and photoaging) illustrate how SFDS can be used to evaluate different multispectral imagers. This approach provides an in-vivo measurement method to evaluate the performance of multispectral imagers specific to their targeted clinical applications and can assist in the design and optimization of new spectral imaging devices.

In Vivo Assessment of Brainstem Depigmentation in Parkinson Disease: Potential as a Severity Marker for Multicenter Studies.

Purpose To investigate the pattern of neuromelanin signal intensity loss within the substantia nigra pars compacta (SNpc), locus coeruleus, and ventral tegmental area in Parkinson disease (PD); the specific aims were (a) to study regional magnetic resonance (MR) quantifiable depigmentation in association with PD severity and (b) to investigate whether imaging- and platform-dependent signal intensity variations can be normalized. Materials and Methods This prospective case-control study was approved by the local ethics committee and the research department of Nottingham University Hospitals. Written informed consent was obtained from all participants before enrollment in the study. Sixty-nine participants (39 patients with PD and 30 control subjects) were investigated with neuromelanin-sensitive MR imaging by using two different 3-T platforms and three differing protocols. Neuromelanin-related volumes of the anterior and posterior SNpc, locus coeruleus, and ventral tegmental area were determined, and normalized neuromelanin volumes were assessed for protocol-dependent effects. Diagnostic test performance of normalized neuromelanin volume was investigated by using receiver operating characteristic analyses, and correlations with the Unified Parkinson's Disease Rating Scale scores were tested. Results Reduction of normalized neuromelanin volume in PD was most pronounced in the posterior SNpc (median, -83%; P < .001), followed by the anterior SNpc (-49%; P < .001) and the locus coeruleus (-37%; P < .05). Normalized neuromelanin volume loss of the posterior and whole SNpc allowed the best differentiation of patients with PD and control subjects (area under the receiver operating characteristic curve, 0.92 and 0.88, respectively). Normalized neuromelanin volume of the anterior, posterior, and whole SNpc correlated with Unified Parkinson's Disease Rating Scale scores (r2 = 0.25, 0.22, and 0.28, respectively; all P < .05). Conclusion PD-induced neuromelanin loss can be quantified across imaging protocols and platforms by using appropriate adjustment. Depigmentation in PD follows a distinct spatial pattern, affords high diagnostic accuracy, and is associated with disease severity. ©RSNA, 2016 Online supplemental material is available for this article.

Non-invasive short-term assessment of retinoids effects on human skin in vivo using multiphoton microscopy.

BACKGROUND: The occlusive patch test developed for assessing topical retinoids activity in human skin has been extended as a short-term screening protocol for anti-ageing agents. In this model, biopsies are performed at the end of the occlusion period for morphological and immuno-histochemistry analysis. Multiphoton microscopy is a recent non-invasive imaging technique that combined with image processing tools allows the in vivo quantification of human skin modifications. OBJECTIVE: To validate with gold standards of anti-ageing that are retinoids, the relevance of multiphoton microscopy for kinetic and quantitative assessment in this model. METHODS: Twenty women, aged 50-65 years, were enrolled. Retinol 0.3% (RO) and Retinoic acid 0.025% (RA) were applied to the dorsal photo-damaged side of their forearm under occlusive patches for 12 days. A patch alone was applied to a third area as control. Evaluation was performed at day D0, D12 (end of treatment), D18 and D32 using multiphoton microscopy. Epidermal thickness, normalized area of the dermal-epidermal junction (DEJ) and melanin density were estimated using 3D image processing tools. RESULTS: Main significant results are: Epidermal thickening at D12, D18 and D32 with RO and at D12, D18 with RA vs. baseline and vs. CONTROL: Increased DEJ undulation at D32 with RO and at D12 with RA vs. baseline and vs. CONTROL: Decreased melanin content with RO (at D12 and D18 vs. baseline and at D32 vs. baseline and vs. control) and with RA (at D12 vs. baseline). CONCLUSIONS: This study shows that multiphoton microscopy associated to specific 3D image processing tools allows cutaneous effects induced by topical retinoids in this in vivo model to be non-invasively detected, quantified and followed over time. This innovative approach could be applied to the evaluation of other active compounds.

Quick analysis of optical spectra to quantify epidermal melanin and papillary dermal blood content of skin.

This paper presents a practical approach for assessing the melanin and blood content of the skin from total diffuse reflectance spectra, R(λ), where λ is wavelength. A quick spectral analysis using just three wavelengths (585 nm, 700 nm and 800 nm) is presented, based on the 1985 work of Kollias and Baquer who documented epidermal melanin of skin using the slope of optical density (OD) between 620 nm and 720 nm. The paper describes the non-rectilinear character of such a quick analysis, and shows that almost any choice of two wavelengths in the 600-900 range can achieve the characterization of melanin. The extrapolation of the melanin slope to 585 nm serves as a baseline for subtraction from the OD (585 nm) to yield a blood perfusion score. Monte Carlo simulations created spectral data for a skin model with epidermis, papillary dermis and reticular dermis to illustrate the analysis.

Estimation of skin optical parameters for real-time hyperspectral imaging applications.

Hyperspectral imaging combines high spectral and spatial resolution in one modality. This imaging technique is a promising tool for objective medical diagnostics. However, to be attractive in a clinical setting, the technique needs to be fast and accurate. Hyperspectral imaging can be used to analyze tissue properties using spectroscopic methods, and is thus useful as a general purpose diagnostic tool. We combine an analytic diffusion model for photon transport with real-time analysis of the hyperspectral images. This is achieved by parallelizing the inverse photon transport model on a graphics processing unit to yield optical parameters from diffuse reflectance spectra. The validity of this approach was verified by Monte Carlo simulations. Hyperspectral images of human skin in the wavelength range 400-1000 nm, with a spectral resolution of 3.6 nm and 1600 pixels across the field of view (Hyspex VNIR-1600), were used to develop the presented approach. The implemented algorithm was found to output optical properties at a speed of 3.5 ms per line of image data. The presented method is thus capable of meeting the defined real-time requirement, which was 30 ms per line of data.The algorithm is a proof of principle, which will be further developed.

Reliability assessment and validation of the postacne hyperpigmentation index (PAHPI), a new instrument to measure postinflammatory hyperpigmentation from acne vulgaris.

BACKGROUND: There are no validated outcome measures for postinflammatory hyperpigmentation (PIH). OBJECTIVE: We sought to determine the reliability and validity of an outcome measure for PIH after acne in patients with skin of color. METHODS: A postacne hyperpigmentation index (PAHPI) was developed. Six raters scored 21 patients with PIH twice. Reliability was determined within and between raters, whereas validity was evaluated by comparing scores with severity ranking by an independent dermatologist. The pigment intensity scores were compared with the melanin index of each patient using a narrowband reflectance spectrophotometer. A quality-of-life score (Skindex-29) was also compared with PAHPI scores. RESULTS: Total PAHPI scores showed good reliability within and between raters and were valid when compared with clinical severity and melanin indices. Good correlation was achieved between the total PAHPI score and the emotion subscale of the Skindex-29. LIMITATIONS: Generalizability of results is limited to African American females. CONCLUSION: The PAHPI shows good reliability and validity when scored on patients with PIH from acne vulgaris. The PAHPI also correlates well with the emotional impact of PIH as measured by the Skindex-29. Future studies should assess the ability of the PAHPI to change with improvement of PIH from acne after treatment.

Estimation of melanin and hemoglobin using spectral reflectance images reconstructed from a digital RGB image by the Wiener estimation method.

A multi-spectral diffuse reflectance imaging method based on a single snap shot of Red-Green-Blue images acquired with the exposure time of 65 ms (15 fps) was investigated for estimating melanin concentration, blood concentration, and oxygen saturation in human skin tissue. The technique utilizes the Wiener estimation method to deduce spectral reflectance images instantaneously from an RGB image. Using the resultant absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin and deoxygenated hemoglobin as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of melanin and total blood are then determined from the regression coefficients using conversion vectors that are numerically deduced in advance by the Monte Carlo simulations for light transport in skin. Oxygen saturation is obtained directly from the regression coefficients. Experiments with a tissue-like agar gel phantom validated the method. In vivo experiments on fingers during upper limb occlusion demonstrated the ability of the method to evaluate physiological reactions of human skin.

3-D volume reconstruction of skin lesions for melanin and blood volume estimation and lesion severity analysis.

Subsurface information about skin lesions, such as the blood volume beneath the lesion, is important for the analysis of lesion severity towards early detection of skin cancer such as malignant melanoma. Depth information can be obtained from diffuse reflectance based multispectral transillumination images of the skin. An inverse volume reconstruction method is presented which uses a genetic algorithm optimization procedure with a novel population initialization routine and nudge operator based on the multispectral images to reconstruct the melanin and blood layer volume components. Forward model evaluation for fitness calculation is performed using a parallel processing voxel-based Monte Carlo simulation of light in skin. Reconstruction results for simulated lesions show excellent volume accuracy. Preliminary validation is also done using a set of 14 clinical lesions, categorized into lesion severity by an expert dermatologist. Using two features, the average blood layer thickness and the ratio of blood volume to total lesion volume, the lesions can be classified into mild and moderate/severe classes with 100% accuracy. The method therefore has excellent potential for detection and analysis of pre-malignant lesions.

Isolation, fractionation and characterization of melanin-like pigments from chestnut (Castanea mollissima) shells.

UNLABELLED: Melanins are known as versatile biopolymers, but the utilizations are restricted by their poor solubilities. Therefore, well soluble ones or their analogs are much desired. In this article, a new procedure was developed for fractionation of the pigments isolated from chestnut (Castanea mollissima) shells, and 3 fractions (Fr. 1, Fr. 2, and Fr. 3) were obtained. The solubilities of all the fractions in waters of different pH and in common organic solvents were studied. The physicochemical properties of the fractions were characterized for the first time on the basis of combined chemical analyses and spectroscopic methods including ultraviolet-visible (UV-Vis), Fourier transform infrared (FT-IR), electron spin resonance (ESR), and solid-state ¹³C nuclear magnetic resonance (¹³C-NMR). All the fractions could be bleached by NaOCl and H2O2 and give a positive reaction for polyphenols, which are usually used as typical tests for allomelanins. Their UV-Vis, FT-IR, and ESR spectra resembled those of synthetic and some natural melanins. Elemental data and quantitative analyses of ¹³C-NMR spectra revealed that pigment-bound proteins and polysaccharides were the most abundant in Fr. 1, while Fr. 2 was presented with the highest aromaticity. PRACTICAL APPLICATION: We provided a new, simple, and inexpensive method to fractionate the melanin-like pigments from chestnut shells. This technique can be used to produce natural melanin-like food colorants with different solubilities from chestnut shells.

Noninvasive imaging of human skin hemodynamics using a digital red-green-blue camera.

In order to visualize human skin hemodynamics, we investigated a method that is specifically developed for the visualization of concentrations of oxygenated blood, deoxygenated blood, and melanin in skin tissue from digital RGB color images. Images of total blood concentration and oxygen saturation can also be reconstructed from the results of oxygenated and deoxygenated blood. Experiments using tissue-like agar gel phantoms demonstrated the ability of the developed method to quantitatively visualize the transition from an oxygenated blood to a deoxygenated blood in dermis. In vivo imaging of the chromophore concentrations and tissue oxygen saturation in the skin of the human hand are performed for 14 subjects during upper limb occlusion at 50 and 250 mm Hg. The response of the total blood concentration in the skin acquired by this method and forearm volume changes obtained from the conventional strain-gauge plethysmograph were comparable during the upper arm occlusion at pressures of both 50 and 250 mm Hg. The results presented in the present paper indicate the possibility of visualizing the hemodynamics of subsurface skin tissue.

New closed-form approximation for skin chromophore mapping.

The concentrations of blood and melanin in skin can be estimated based on the reflectance of light. Many models for this estimation have been built, such as Monte Carlo simulation, diffusion models, and the differential modified Beer-Lambert law. The optimization-based methods are too slow for chromophore mapping of high-resolution spectral images, and the differential modified Beer-Lambert is not often accurate enough. Optimal coefficients for the differential Beer-Lambert model are calculated by differentiating the diffusion model, optimized to the normal skin spectrum. The derivatives are then used in predicting the difference in chromophore concentrations from the difference in absorption spectra. The accuracy of the method is tested both computationally and experimentally using a Monte Carlo multilayer simulation model, and the data are measured from the palm of a hand during an Allen's test, which modulates the blood content of skin. The correlations of the given and predicted blood, melanin, and oxygen saturation levels are correspondingly r = 0.94, r = 0.99, and r = 0.73. The prediction of the concentrations for all pixels in a 1-megapixel image would take ∼ 20 min, which is orders of magnitude faster than the methods based on optimization during the prediction.

Objective scar assessment--a new method using standardized digital imaging and spectral modelling.

INTRODUCTION: Quantitative assessment of scars is needed in clinical practice and in scientific studies. To date, there have been no entirely objective methods available for these purposes. We introduce a new method developed for scar assessment combining standardized digital imaging (SDI) and spectral modelling (SpM). With this method, the estimated concentration changes (ECCs) of haemoglobin and melanin in the scar can be determined quantitatively. PATIENT AND METHODS: In the current study, 22 skin graft donor site (SGDS) wounds were treated with two alternative dressing materials, Suprathel® and Mepilex Transfer®, side by side on the same wound. The SGSD scars were assessed using SDI and SpM. The scars were given subjective ratings by three surgeons using the POSAS and the Vancouver Scar Scale (VSS). The correlations between the ECCs of melanin and haemoglobin and the corresponding subjective ratings were calculated as well as the Intraclass Correlation Coefficient (ICC) of the subjective ratings. RESULTS: There was a statistically significant correlation between the ECCs of melanin and haemoglobin and the subjective ratings. A single observer could reliably assess pigmentation with the POSAS scale (ICC = 0.75) but not vascularity (ICC = 0.51). The reliability ratings of the VSS were unacceptably low. CONCLUSIONS: The ECC values of haemoglobin and melanin give accurate documentation of the scar status. The results also show that the subjective ratings in this study were unreliable especially when interfering pigmentation and increased vascularity were both present at the same time.

Rapid and accurate estimation of blood saturation, melanin content, and epidermis thickness from spectral diffuse reflectance.

We present a method to determine chromophore concentrations, blood saturation, and epidermal thickness of human skin from diffuse reflectance spectra. Human skin was approximated as a plane-parallel slab of variable thickness supported by a semi-infinite layer corresponding to the epidermis and dermis, respectively. The absorption coefficient was modeled as a function of melanin content for the epidermis and blood content and oxygen saturation for the dermis. The scattering coefficient and refractive index of each layer were found in the literature. Diffuse reflectance spectra between 490 and 620 nm were generated using Monte Carlo simulations for a wide range of melanosome volume fraction, epidermal thickness, blood volume, and oxygen saturation. Then, an inverse method was developed to retrieve these physiologically meaningful parameters from the simulated diffuse reflectance spectra of skin. A previously developed accurate and efficient semiempirical model for diffuse reflectance of two layered media was used instead of time-consuming Monte Carlo simulations. All parameters could be estimated with relative root-mean-squared error of less than 5% for (i) melanosome volume fraction ranging from 1% to 8%, (ii) epidermal thickness from 20 to 150 mum, (iii) oxygen saturation from 25% to 100%, (iv) blood volume from 1.2% to 10%, and (v) tissue scattering coefficient typical of human skin in the visible part of the spectrum. A similar approach could be extended to other two-layer absorbing and scattering systems.

Transscleral visible/near-infrared spectroscopy for quantitative assessment of melanin in a uveal melanoma phantom of ex vivo porcine eyes.

Optical spectroscopy has been used as a supplement to conventional techniques for analyzing and diagnosing cancer in many human organs. Because ocular tumors may be characterized by their different melanin content, we investigated the feasibility of using transscleral visible/near-infrared spectroscopy (Vis/NIRS) to estimate the quantity of melanin in a novel uveal melanoma phantom of ex vivo porcine eyes. The phantoms were made by injecting a freshly prepared suspension of 15% (wt/vol) gelatin, 10 mg/ml titanium dioxide (TiO(2)), and natural melanin, isolated from the ink sac of cuttlefish (Sepia officinalis), into the suprachoroidal space of 30 enucleated porcine eyes. The melanin concentrations used were 1 mg/ml, 2 mg/ml, and 3 mg/ml, with 10 eyes in each group. After gelation, the size and location of the phantoms were documented by B-scan ultrasonography and transillumination. Vis/NIRS recordings, covering the wavelength region from 550 to 1000 nm, were performed with two optical fibers separated by 6 mm to deliver and collect the light through the sclera. During all measurements, the exact pressure exerted by the fiber probe on the scleral surface was monitored by placing the eye on an electronic scale. Transscleral Vis/NIRS was performed across the phantom inclusion, as well as on the opposite (normal) side of each eye. A total of three consecutive measurements were carried out alternately on each side of the globe. The spectral data were analyzed using partial least squares regression. In the melanin concentration groups of 1 mg/ml (n = 10), 2 mg/ml (n = 10), and 3 mg/ml (n = 10), the largest basal phantom diameters (mean +/- SD) were 14.9 +/- 1.6 mm, 14.6 +/- 1.5 mm, and 14.3 +/- 1.0 mm, respectively (p > 0.05). The largest phantom thicknesses (mean +/- SD) were 4.0 +/- 0.5 mm, 4.4 +/- 0.7 mm, and 4.5 +/- 0.5 mm, respectively (p > 0.05). Statistical regression modeling of the Vis/NIRS data revealed that it was possible to correctly classify the phantoms according to their melanin concentrations in 84.4% of cases. The correct classification rate for phantoms with the lowest (1 mg/ml) and highest (3 mg/ml) melanin concentrations was 99.2%. The study demonstrates that transscleral Vis/NIRS is a feasible and accurate method for predicting the content of melanin in choroidal lesions.

Assessment of nurse-led screening of pigmented lesions using SIAscope.

UNLABELLED: The incidence of malignant melanoma in the UK is rising. Increased awareness of melanoma has led to an increase in patients presenting with pigmented lesions to their general practitioner (GP) and to pigmented lesion clinics. The sensitivity and specificity of the general practitioner in diagnosing melanoma remains poor. OBJECTIVES: A trial was conducted to establish the effectiveness of SIAscope in triaging patients referred by GPs on suspicion of melanoma. MATERIALS AND METHODS: After Ethical Committee approval, all consenting patients attending the Pigmented Lesion Clinic at Frenchay Hospital were scanned with the SIAscope. The consultant then examined all the patients and all suspicious lesions were excised and examined. RESULTS: Eight hundred and eighty-six patients were included in the trial. The SIAscope had a sensitivity of 94.4% with a false negative rate of 3.7% for malignant melanoma. CONCLUSIONS: The SIAscope could be useful in reducing the number of benign lesions seen by the consultant while still identifying most melanomas.

Estimation of melanin and hemoglobin in skin tissue using multiple regression analysis aided by Monte Carlo simulation.

To estimate the concentrations of melanin and blood and the oxygen saturation in human skin tissue, we propose a method using a multiple regression analysis aided by a Monte Carlo simulation for diffuse reflectance spectra from the skin tissue. By using the absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin, and deoxygenated hemoglobin as predictor variables, the multiple regression analysis gives regression coefficients. The concentrations of melanin and blood are determined from the regression coefficients using conversion vectors that are estimated numerically in advance, while the oxygen saturation is obtained directly from the regression coefficients. Numerical and experimental investigations were performed for layered skin tissue models and phantoms. Measurements of human skin were also carried out to monitor variations in the melanin and blood contents and oxygenation during cuff occlusion. The results confirmed the usefulness of the proposed method.