Real Skin Research Articles

Skin color modeling using the radiative transfer equation solved by the auxiliary function method

The auxiliary function method is an efficient technique for solving the radiative tranfer equation without adding any assumption and was applied until now only for theoretical stratified media. The first application (to our knowledge) of the method to a real case, the human skin, is presented. This makes it possible to validate the method by comparing model results with experimental reflectance spectra of real skin. An excellent agreement is obtained for a multilayer model of the skin made of 22 sublayers and taking into account the anisotropic phase function of the scatterers. Thus there is the opportunity to develop interest in such models by quantitatively evaluating the influence of the parameters commonly used in the literature that modify skin color, such as the concentration of the scatterers and the thickness of each sublayer.

Skin surface model material as a substrate for adhesion-to-skin testing

A model material simulating the mechanical and surface properties of a real human skin was developed for use as a substrate in adhesion-to-skin evaluation. It is a protein–lipid composition possessing film-forming ability. The composition is based on gelatin plasticized by glycerol, polysaccharides and a mixture of lipids that mimick the skin's lipid structure and creates a hydrophobic surface. To enhance the material hydrolytic stability, the composition was cross-linked by formaldehyde, producing a water-swellable but insoluble matrix. The surface topography of a real skin was achieved by a silicone replica technique. Thin films with thickness of 100 ± 10 μm were cast. The effect of the components ratio and preparation technique on the film mechanical, surface and hydrolytic properties was studied. Based on the results obtained, a formulation having mechanical and surface properties comparable to that of a human skin was selected. The relevance of the model material was evaluated in lap-shear and 180°-peel adhesion tests and the results were compared to a finger or a forearm skin of ten healthy volunteers (in vivo tests). For validation purposes, commercial surgical tapes Micropore™ and Transpore™ and Mylar® polyester film were also used. The effects of substrate, adhesive, conditions of the joint preparation and the test employed on adhesion strength were studied. The results obtained show that the mechanical and surface properties of the model material are close to those of the human skin.

Artificial fingerprint recognition by using optical coherence tomography with autocorrelation analysis

Fingerprint recognition is one of the most widely used methods of biometrics. This method relies on the surface topography of a finger and, thus, is potentially vulnerable for spoofing by artificial dummies with embedded fingerprints. In this study, we applied the optical coherence tomography (OCT) technique to distinguish artificial materials commonly used for spoofing fingerprint scanning systems from the real skin. Several artificial fingerprint dummies made from household cement and liquid silicone rubber were prepared and tested using a commercial fingerprint reader and an OCT system. While the artificial fingerprints easily spoofed the commercial fingerprint reader, OCT images revealed the presence of them at all times. We also demonstrated that an autocorrelation analysis of the OCT images could be potentially used in automatic recognition systems.

Acyclovir concentrations in the skin of humans after a single oral dose assessed by in vivo cutaneous microdialysis

Acyclovir is a synthetic deoxyguanosine analogue used in the treatment of certain viral diseases. This drug is effective primarily against Herpes simplex virus, Varicella zoster virus and to a lesser extent against Epstein-Barr virus and cytomegalovirus. The aim of the study was to determine the acyclovir concentrations in plasma and skin (cutaneous microdialysate) and to compare its penetration into real (skin) and theoretical peripheral compartment after administration of a single 0.4 g oral dose. To evaluate the skin concentrations of the examined agent in 10 healthy male volunteers linear microdialysis probes with 2 kDa molecular-weight cut-off were inserted intradermally and were perfused with Ringer solution up to 6 h after drug ingestion. The mean maximum acyclovir concentrations in the plasma, skin and theoretical peripheral compartment were 3.16+/-0.86, 0.94+/-0.34 and 1.85+/-0.69 micromol/L, respectively, and were achieved after 1.6+/-0.4, 2.4+/-0.3 and 3.7+/-0.7 h. The degree of penetration into the real (skin) and theoretical peripheral compartment was 0.36+/-0.15 and 0.74+/-0.12, respectively, and the differences were statistically significant. Similarly, also, the maximum concentration, time to maximum concentration and area under the concentration-time curve differed significantly between the plasma and skin as well as between the skin and the theoretical peripheral compartment. In selected cases skin concentrations should be determined rather than those in blood plasma when studying the distribution of orally administered drugs. Evaluation of acyclovir concentrations in the skin cannot be replaced by the calculation of the theoretical peripheral compartment.

Le moi-peau

To construct a coherent identity, humans must distinguish what belongs to the external, perceived world from what belongs to their own inner world and the inner world of other individuals. Based on the theory developed by S. Freud and on work by ethologists, a number of psychoanalysts (J. Bowlby, R.A. Spitz, D.W. Winnicott, etc.) have underlined the importance of early tactile exchanges with the mother if a child is to become an autonomous individual who feels secure within what he or she perceives to be sound and reliable mental and physical boundaries. More recently, other psychoanalysts (E. Bick, W.R. Bion, etc.) have studied the fantasized mental structures that form the limits between an individual's inner mental space and the external world (including other individuals). As part of this theoretical psychoanalytical movement, Didier Anzieu, a French psychoanalyst, started to develop the concept of the "Moi-peau" in 1974. The "Moi-peau" designates a fantasized reality that a child uses during its early development to represent itself as "me", based on its experience of the body surface. The child, enveloped in its mother's care, fantasizes of a skin shared with its mother: on one side the mother (the outer layer of the "Moi-peau"), and on the other side the child (the inner layer of the "Moi-peau"). These two layers must separate gradually if the child is to acquire its own me-skin. D. Anzieu's work allowed dermatologists and other specialists, such as pediatricians, to focus on the quality of early tactile exchanges between a mother and her child, including the child with a chronic skin disorder. It also helped dermatologists to recognize patients with "borderline" states, which are particularly frequent in dermatology (ereutophobia, dysmorphophobia, tattooing, self-mutilation, artefacta dermatitis). These borderline patients are adults who, as a result of their mental conflicts, adopt defense mechanisms derived from both neurotic and psychotic functioning. Their complaints reflect difficulties with the solidity of their mental and physical limits: their real skin is metaphorically linked to the fantasized mental structure that delimits the individual mental space. Among other clinical characteristics, they have a "pathology of action" and frequently attack their own skin, paradoxically, in order to test the solidity and reliability of their own limits. Finally, D. Anzieu's work encouraged dermatologists to use psychotherapeutic approaches in parallel to classical dermatologic approaches, when necessary, and helped them better understand how psychoanalysts work with patients who have not yet acquired their own "Moi-peau". As a result, D. Anzieu was among the first to reconcile dermatologists and psychoanalysts.

Validity and Reliability of an Alginate Method to Measure Body Surface Area

The purpose of this study was to evaluate the validity and reliability of coating methods (plaster bandage, inelastic tape, and the alginate method) and an indirect method using a three dimensional (3D) whole body scanner. The surface area of geometric solids was measured five times using the three coating methods, and analyzed through 2D scanning and a planimeter. Second, to examine the accuracy of the alginate method more closely, the surface areas of boards with different surface properties at various inclines were measured and compared. Lastly, the surface area of a human arm was measured using the three coating methods and a 3D scanning method. The results are as follows: 1) The three coating methods were statistically valid and reliable for measuring the surface area of geometric solids. 2) The planimeter was rejected because the mean error was bigger than in 2D scanning. 3) The method showing the least error was the inelastic tape method, but that method was not recommended because it was too tiresome and laborious. 4) The greater the curvature and smaller the size of a geometric solid, the greater the error. 5) In measuring surface area using the alginate method, the objects that were smoother and had steeper angles showed a greater surface area: however, the mean error was less than 1%. 6) In measuring a human arm, the surface area obtained by 3D scanning was less than any other surface area obtained in the three coating methods, because the 3D scanner could not discern the armpit and fingers. In conclusion, the method using alginate was statistically valid and reliable in the measuring of surface area both of geometric solids and real human skin.

Skin and psyche: Diversionary symbiosis

A significant proportion of patients with skin diseases have associated psychosocial factors. Not only does psychopathology manifest on the skin in absence of any real skin disease, primary skin disorders can also be exacerbated by emotional stress adversely influencing the homeostasis of immunological and inflammatory processes in deeper layers of the skin. Furthermore, many patients develop emotional problems as a result of having disfiguring skin diseases. In addition, some patients having solely sensory disturbances in absence of primary dermatoses or identifiable medical or neurological conditions, as well as some purely dermatologic conditions such as post-herpetic neuralgia may preferentially need psychotherapeutic modalities to address their underlying psychopathology irrespective of the presenting dermatologic manifestation arising out of ‘somatisation’ of a psychopathology into physical problems. The most obvious course of action of referral to a psychiatrist or another mental health professional may unfortunately not be readily tenable either due to the perceived stigma associated with psychiatric illness or lack of insight on the part of patients. In the interregnum, effective management of the psychologic or/and psychiatric problems can only be done by the dermatologist provided he has an adequate knowledge base and experience to undertake psychotherapeutic modalities.

Application of region-based segmentation and neural network edge detection to skin lesions

This paper proposes two approaches to the skin lesion image segmentation problem. The first is a mainly region-based segmentation method where an optimal threshold is determined iteratively by an isodata algorithm. The second method proposed is based on neural network edge detection and a rational Gaussian curve that fits an approximate closed elastic curve between the recognized neural network edge patterns. A quantitative comparison of the techniques is enabled by the use of synthetic lesions to which Gaussian noise is added. The proposed techniques are also compared with an established automatic skin segmentation method. It is demonstrated that for lesions with a range of different border irregularity properties the iterative thresholding method provides the best performance over a range of signal to noise ratios. Iterative thresholding technique is also demonstrated to have similar performance when tested on real skin lesions.

Hierarchical facial data modeling for visual expression synthesis

This paper presents a new method for modeling of a personalized 3D face model that has a hierarchical structure of the skin, muscle, and skull for realistic expression synthesis. We start from an accurate facial mesh reconstructed from the individual face measurements. The deformable skin model has a multi-layer structure to approximate different types of soft tissue and takes into account the nonlinear stress-strain relationship and incompressibility of the real skin. The 3D face model incorporates the skull structure which extends the scope of facial motion and facilitates interactive facial muscle insertion. Under the muscular force, the deformation of the facial skin is evaluated by the numerical integration of the governing Lagrangian dynamics. The resulting animation system enables realistic facial expressions to be dynamically synthesized.

In vitro Evaluation of Skin Sensitivity of Povidone-Iodine and Other Antiseptics Using a Three-Dimensional Human Skin Model

Povidone-iodine (PVP-I) is an antiseptic which has been widely used in various fields. It was reported to have a weaker skin irritancy than other antiseptics in the Draize skin irritation test using rabbits. Recent increased concern for animal welfare requires us to use skin models in the tests as an alternative to animal testing. Actually, there are some skin models already commercialized, which are available to evaluate skin irritancy caused by e.g. chemical reagents, cosmetics or medicines. In this study, we evaluated the potential of a PVP-I solution and other antiseptics to cause irritation using a cultured human skin model (three-dimensional skin model) under conditions similar to clinical use. This skin model has two layers like a real skin, such as the dermis and epidermis which includes the cornified layer. For the evaluation of skin irritancy in this model, cell viability was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay as an endpoint. Antiseptic formulations such as benzalkonium chloride (BAC), benzethonium chloride (BEC), chlorhexidine gluconate (CHG) and alkyldiaminoethylglycine hydrochloride (AEG) were used in this study. As a result, PVP-I showed a significantly weaker skin irritancy compared to the other antiseptics. The present in vitro study results revealed a correlation with the results of previously conducted in vivo skin irritancy tests using rabbits.

Opto-Thermal Inverse Modelling Using a Maximum Entropy Approach

We present a new scheme for the inverse analysis of opto-thermal transients by using Maximum Entropy Methods (MEM). Unlike other inverse methods, MEM is naturally positively constrained, and has the ability to incorporate a-priori knowledge of the problem, such as laser energy conservation constrains. Using entropy as a regularization function, MEM is capable of calculating initial temperature profiles from noisy, incomplete data, despite the ill-conditioning. This is particularly useful for tackling problems where the inhomogeneities of the sample are insufficiently well understood, such as skin disease characterisation and skin pigment (melanin and haemoglobin) depth profiling. MEM reconstruction of initial temperature profiles using both simulated data and real in-vivo skin measurements are presented.

Quantitative model calculation of the time-dependent protoporphyrin IX concentration in normal human epidermis after delivery of ALA by passive topical application or lontophoresis.

We present a mathematical layer model to quantitatively calculate the diffusion of 5-aminolevulinic acid (ALA) in the skin in vivo, its uptake into the cells and its conversion to protoporphyrin IX (PpIX) and subsequently to heme. The model is a modification and extension of a recently presented three-compartment model. The diffusion of ALA in the skin (epidermis, dermis) is described by the time-dependent diffusion equation, and the sink in this equation accounts for ALA uptake in the cells. As boundary conditions, we use the ALA flux across the human stratum corneum (SC) in vitro during passive or iontophoretic ALA delivery as measured in vitro. Besides the diffusion equation, the model includes three additional equations, similar in form to those of the three-compartment model but with a different interpretation. Our additional equations are supposed to describe, respectively, the conversion of ALA in the cytoplasm to some intermediate compound in the mitochondria and the conversion of the latter to PpIX and of PpIX to heme. The first conversion is a process of the Michaelis-Menten type, the other two are first-order rate processes. When fitted to the published data of PpIX fluorescence from normal human skin following iontophoresis of ALA, the model yields the tissue concentration of PpIX as a function of time after ALA application. The computed concentrations are in good agreement with the published phototoxic concentrations of PpIX in the tissues obtained from extraction. The model parameters obtained from the fit are subsequently used to compute the PpIX concentration in normal human skin after 4 h topical application of 10, 20 and 40% ALA. This again yields the PpIX concentrations in tissue, in good agreement with the published values. The saturation of the PpIX concentration as a function of applied ALA concentration is calculated and agrees with clinical observations on the effectiveness of photodynamic therapy. Photobleaching is simulated, with subsequent resynthesis of PpIX in qualitative agreement with experiment. Finally, the model predicts that only 2.5-3.5% of the ALA entering the skin after passing the SC is converted to PpIX. The layered model is a considerable simplification of real skin, but its successful qualitative and quantitative reproduction of experimental data may encourage further studies to test and refine the model to improve our understanding of the kinetics of ALA and the synthesis of PpIX in the skin.

Fatigue Crack Initiation and Early Growth in GLARE 3 Fiber-metal Laminate Subjected to Mixed Tensile and Bending Loading

A special open-hole sheet specimen of GLARE fiber-metal laminate was used to simulate mixed loading similar to the loading of a riveted hole in a real fuselage skin structure. The effect of cyclic tension and secondary bending loading was studied. The notch region was observed through a microscope in order to detect the first fatigue crack initiation during fatigue loading. The number of cycles prior to crack initiation was measured, and the crack growth rate in the surface layer of the laminate was evaluated. The specimens were subjected to fatigue damage investigation in the inner layers of the laminate after termination of the test. A significant effect of secondary bending on fatigue crack initiation and early crack growth was found. The experimental results are discussed in terms of local stress-strain conditions in the notch region evaluated by means of finite element calculation.

Three-dimensional CT-Guided Bronchoscopy With a Real-Time Electromagnetic Position Sensor: A Comparison of Two Image Registration Methods

To compare two different image registration methods for accurately displaying the position of a flexible bronchoscope on a previously acquired three-dimensional CT scan during bronchoscopy. Bronchoscopy suite of a university hospital. Fifteen adult patients scheduled for nonemergent bronchoscopy. A miniature electromagnetic position sensor was placed at the tip of a flexible bronchoscope. Previously acquired three-dimensional CT scans were registered with the patient in the bronchoscopy suite. Registration method 1 used multiple skin fiducial markers. Registration method 2 used the inner surface of the trachea itself for registration. Method 1 was objectively assessed by measuring the error distance between the real skin marker position and the computer display position. Methods 1 and 2 were subjectively assessed by the bronchoscopist correlating visual bronchoscopic anatomic location with the computer display position on the CT image. The error distance (+/- SD) from known points for registration method 1 was 5.6 +/- 2.7 mm. Objective error distances were not measured for method 2 because no accurate placement of the bronchoscope sensor could be correlated with CT position. Subjectively, method 2 was judged more accurate than method 1 when compared with the fiberoptic view of the airways through the bronchoscope. Additionally, method 2 had the advantage of not requiring placement of fiducial markers before the CT scan. Respiratory motion contributed an error of 3.6 +/- 2.6 mm, which was partially compensated for by a second tracking sensor placed on the patient's chest. Image registration method 2 of surface fitting the trachea rather than method 1 of fiducial markers was subjectively judged to be superior for registering the position of a flexible bronchoscope during bronchoscopy. Method 2 was also more practical inasmuch as no special CT scanning technique was required before bronchoscopy.

Psychodermatology: A practical manual for clinicians

Psychodermatology: A practical manual for clinicians

Real and Apparent Tuberculin Skin Test Conversions in a Group of Medical Students

Real and Apparent Tuberculin Skin Test Conversions in a Group of Medical Students

Oscillating sedimentation of spheres in viscoplastic fluids

In applications of chemical engineering often the sedimentation is used to separate disperse particles from liquid phases. Some real liquids, e.g., polymer fluids, paints, and skin creams show viscoplastic flow behavior, i.e., they have a yield stress. In such fluids it is possible that suspended particles do not move under action of gravity although the density of the particles is greater than the fluid density. A possibility to sediment stuck spherical particles is shown. The fluid is set in sinusoidal vibration so that the particles undergo forced oscillations. This effect is investigated for single spheres. A model is given and several theoretical results are discussed. A criterion is presented that allows one to predict the combinations of the vibration parameters (amplitude and frequency) which are needed to sediment the spheres. The theoretical investigations are confirmed by experiments. The motion of several glass and steel spheres in an oscillating tube filled with aqueous carbopol solutions are detected. The comparison between theory and experiment shows good agreement.

Neural network diagnosis of malignant melanoma from color images.

Malignant melanoma is the deadliest form of all skin cancers. Approximately 32,000 new cases of malignant melanoma were diagnosed in 1991 in the United States, with approximately 80% of patients expected to survive five years [1]. Fortunately, if detected early, even malignant melanoma may be treated successfully. Thus, in recent years, there has been rising interest in the automated detection and diagnosis of skin cancer, particularly malignant melanoma [2]. In this paper, we present a novel neural network approach for the automated separation of melanoma from three benign categories of tumors which exhibit melanoma-like characteristics. Our approach uses discriminant features, based on tumor shape and relative tumor color, that are supplied to an artificial neural network for classification of tumor images as malignant or benign. With this approach, for reasonably balanced training/testing sets, we are able to obtain above 80% correct classification of the malignant and benign tumors on real skin tumor images.

Analysis of Pressure Data From a Restricted-Entry Well in a Multilayer Reservoir

Summary This work presents new semilog type curves for analyzing data obtained at a restricted-entry well completed in a multilayer reservoir where crossflow occurs between reservoir layers. Use of the new type curves along with standard semilog analysis of pseudoradial-flow pressure data makes possible a complete analysis of pressure data. Specifically, standard semilog analysis of pseudoradial-flow pressure data yields estimates of the total flow capacity and the total skin factor. The new type curves can then be used to estimate the real mechanical skin factor resulting from damage or stimulation, the flow capacity adjacent to the open (perforated) interval, and the effective average vertical permeability.

Relationship between evaporation rate of sweat and mean sweating rate

The rate of evaporation of sweat under a step change of ambient temperature (30-45 degrees C) was compared with the mean sweating rate (MSR) computed from five simultaneous resistance hygrometric measurements. Empirical equations derived for the conditions studied enabled a direct conversion from hygrometric measurements into real evaporative sweat losses and skin wetness for all phases of sweat evaporation. From five chosen skin areas, forehead, forearm, chest, thigh, and calf, it was found that none of these sites gave a local sweating response close to the MSR. In the subjects with a forehead sweating rate within +/- 39% of the MSR, at least four hygrometric sensors were needed to predict the rate of sweat evaporation. For subjects with higher forehead sweating rates, at least five sensors were necessary to calculate the evaporative sweat loss.