Digital camera images obtained using a light-emitting diode illuminator and their dermatological applications

BACKGROUND/PURPOSE: Although digital cameras have powerful macrocapabilities, flash macrophotographs are often unsatisfactory. The aim of this study was to develop a light-emitting diode (LED) illuminator for macro digital photography that allows colorimetric investigations of the skin. METHODS: We devised an LED illuminator suitable for acquiring super-macro digital images of the skin. Reference CIELAB color chart values were compared statistically with computed values from digital images in order to obtain equations for real CIELAB values. Using these, we acquired and analyzed images of various dermatological conditions using an LED illuminator. RESULTS: The images obtained with the devised LED illuminator were more reproducible than flash-assisted photographs. With proper camera settings, the devised LED illuminator and the color analysis method developed during this study provided digital skin images containing colorimetric information. CONCLUSION: A digital camera equipped with an LED illuminator is a useful tool for dermatological research and clinical practice.     

SkinChip®, a new tool for investigating the skin surface in vivo

Background/aims: Non-invasive methods used for characterizing skin micro-relief and skin surface hydration were developed in the 1980s. Although they allowed some progress in the knowledge of skin properties, they are not completely satisfactory in many aspects. Today, new technologies are emerging that may address such issues.
Methods: We adapted the technology produced by the ST Microelectronics Company for sensing fingerprint for the measurement of skin surface properties. Accordingly, we developed acquisition software for obtaining routinely the distribution of skin surface capacitance along different body sites. Image analysis softwares were also processed for collecting both the main orientations of the micro-relief lines and their density. The average value of skin capacitance is also obtained.
Results: The images allow a highly precise observation of the skin topography that can be easily quantified in terms of line density and line orientation. The mean gray levels of the images appear much closely correlated to the Corneometer values.
Conclusion: This new device appears to be a very convenient way for characterizing the properties of the skin surface. With regard to hydration, it usefully provides both the average value and the hydration chart of the investigated skin zones.     

Development and validation of a new Skin Color Chart®

BACKGROUND: Age-induced skin color variations are of great importance and incite increasing demand for cosmetic products to improve the appearance. The evaluation by clinicians or estheticians of the efficacy of skin care products is particularly difficult and requires the help of color charts. PURPOSE: To standardize this kind of evaluation, we have developed a new Skin Color Chart. In contrast to other color charts, this new one represents true skin color without metamerism and covers almost all skin colors encountered around the world. This new instrument has been validated for both Asian and Caucasian skin complexion and sun spot color. METHOD: The new device used to record skin color, the Chromasphere, developed by L'Oréal, is briefly presented. All skin color measurements and the validation of each selected Color were performed under identical conditions, and then, absorption spectra of both skin and chart were compared using severe criteria. The first use and the validation of this Skin Color Chart were performed by dermatologists (two in China and one in France) in groups of about 40 women on sunspots and complexion color. RESULTS: Regarding repeatability (intraobserver agreement), the new Skin Color Chart showed very good statistical validation on complexion and sunspot color. The agreement between dermatologists, the reproducibility criterion, although not as good remained high. An example of the evaluation of the efficacy of a whitening product is given in order to illustrate the 'sensitivity' of this new device to evaluate very weak color variations. CONCLUSIONS: The new Skin Color Chart appears to be very useful and easy to use even by clinicians without training in color evaluation.     

Fluorescent image analysis for evaluating the condition of facial sebaceous follicles

Background/purpose: Conventional methods, such as 'Sebutape' and 'Sebumeter,' can provide quantitative information on sebum excretion but cannot reflect the condition of sebaceous follicles that can be indirectly evaluated with fluorescent colors of sebum. The images of sebum excretion can be obtained with an ultraviolet-A light that is generally called 'Wood's Lamp.' In this study, we describe fluorescent image analysis methods for the detection of sebum and the color segmentation of sebum to evaluate the condition of sebaceous follicles.
Methods/results: For subject-dependent automatic image analysis, we extracted calibrated image analysis methods that were optimized for digital fluorescent images acquired from our imaging system. The calibrated subjective threshold values for sebum detection were determined by statistically analyzing the number of sebum detected by the automatic threshold value method and the subjective threshold value method ( R =0.947, the number of volunteers: 29). In fluorescent color analysis of sebum, the calibrated reference color markers for the red and white colors were extracted with a coefficient of variance of <10%.
Conclusion: We are confident that such calibrated image analysis methods in combination with our imaging system can provide useful quantitative diagnostic information for sebum-related skin pathologies.     

Utilization of a high-resolution digital imaging system for the objective and quantitative assessment of hyperpigmented spots on the face

Background/aims:   The aim of this study was to quantify and confirm the efficacy of cosmetic formulations for hyperpigmented spots over a wide area of the face using a high quality digital imaging system that we developed.
Methods:   A total of 120 Japanese female volunteers aged 25–60 years with solar lentigines were treated for 6 months with a skin lightening moisturizer (SLM, thereafter) containing 3% magnesium ascorbyl phosphate on one side of the face and vehicle on the other side. During the course of the study, facial images were collected by the image analysis to measure facial skin colour and the total area of hyperpigmented spots. The evaluation was also conducted by visual grading. Measurements were made before and 1, 3, and 6 months after starting the application, and again 6 months after discontinuing the treatment. Three similar clinical studies using the same protocol were repeated for up to one-month to confirm the reproducibility of the results and to examine seasonal variation.
Results:   SLM significantly reduced the total area of hyperpigmented spots ( P  < 0.005) after one month of treatment compared to the vehicle, with no significant variation in facial skin colour tone in the areas outside the hyperpigmented spots. The results of the visual grading were consistent with those obtained by image analysis. The total area of hyperpigmented spots 6 months after discontinuing the treatment had returned to pre-treatment levels. The reproducibility of these clinical results was demonstrated in three follow-up studies.
Conclusions:   A high-resolution digital imaging method, combined with a split-face clinical protocol is sensitive enough to prove that SLM readily reduces hyperpigmented spots, while maintaining normal facial skin colour.     

Influence of age on the wrinkling capacities of skin

Background: Comparisons of clinical assessment with measurement of physical parameters are rare.
Objective: To standardize the horizontal wrinkling of the skin in order to define a reference chart of the different wrinkling grades and to propose an interpretation of the clinical pattern in terms of skin layers thickness and mechanical parameters.
Methods: A device allowing reproducible wrinkling of the skin was made. The skin folds created in this way were clinically assessed on women of different ages. Measurements of the mechanical properties of the skin were carried out by using a Torquemeter. Skin layers' thicknesses were measured by using in vivo Confocal Microscopy (CM) and Ultrasound Imaging (B mode).
Results: Skin wrinkling grades increase versus age. Skin elasticity, extensibility and echogenicity decrease also versus age and the wrinkling grade. Wrinkling appears to be related to skin rigidification (for both stratum corneum and dermis) coupled to a certain weakening of the upper dermis (loss of echogenicity).
Conclusion: This study points out the key role of the age-related alterations of the upper dermis in skin wrinkling capacities.     

Feasibility and accuracy of a newly developed hand-held device with a flat-type fluorescent lamp for measuring the minimal erythema dose for narrow-band UVB therapy

Background: Narrow-band ultraviolet B (NB-UVB) for the treatment of refractory skin diseases, such as psoriasis and atopic dermatitis, requires an adequate irradiation protocol based on the minimal erythema dose (MED) to establish an optimal dosage schedule. Although MED can be measured using a systemic-type irradiation unit, there are difficulties associated with this device. There is no standardized device available to determine the MED for NB-UVB. Here, we compared a conventional device with a newly developed device for measuring MED.
Method: MED was measured in 16 psoriasis patients using both a conventional measuring device and the newly developed device, which comprised a hand-held NB-UVB (311–313 nm) flat-type fluorescent lamp with neutral density filters having different transmittances ranging from 10% to 90%. This device was designed to be stably maintained on the skin surface and to provide a highly accurate measurement with only one UV irradiation exposure while also preventing UV radiation from leaking to nonirradiated areas.
Results: The MED values obtained from each patient were the same using both devices.
Conclusion: One-time irradiation using the new hand-held device with the NB-UVB flat-type fluorescent lamp is feasible and accurate for determining the MED to use in calculating the UV irradiation treatment dose.     

Extraction of skin lesion texture features based on independent component analysis

Background/purpose: During the recent years, many diagnostic methods have been proposed aiming at early detection of malignant melanoma. The texture of skin lesions is an important feature to differentiate melanoma from other types of lesions, and different techniques have been designed to quantify this feature. In this paper, we discuss a new approach based on independent component analysis (ICA) for extraction of texture features of skin lesions in clinical images.
Methods: After preprocessing and segmentation of the images, features that describe the texture of lesions and show high discriminative characteristics are extracted using ICA, and then these features, along with the color features of the lesions, are used to construct a classification module based on support vector machines for the recognition of malignant melanoma vs. benign nevus.
Results: Experimental results showed that combining melanoma and nevus color features with proposed ICA-based texture features led to a classification accuracy of 88.7%.
Conclusion: ICA can be used as an effective tool for quantifying the texture of lesions.     

Using 3D differential forms to characterize a pigmented lesion in vivo

Background/purpose: After the formulation of ABCD rules, many new feature extraction methods are emerging to describe the asymmetry, border irregularity, color variation and diameter of malignant melanoma. In this paper, a new research direction orthogonal to ABCD rules that characterizes 3D local disruption of skin surfaces to realize automatic recognition of melanoma is described.
Methods: This paper examines 3D differential forms of skin surfaces to characterize the local geometrical properties of melanoma. Firstly, 3D data of skin surfaces are obtained using a photometric stereo device. Then differential forms of lesion surfaces are determined to describe the geometrical texture patterns involved. Using only these geometrical features, a simple least-squared error-based linear classifier can be constructed to realize the classification of malignant melanomas and benign lesions.
Results: As with the 3D data of 35 melanoma and 66 benign lesion samples collected from local pigmented lesion clinics, the optimal sensitivity and specificity of the constructed linear classifier are 71.4% and 86.4%, respectively. The total area enclosed by the corresponding receiver operating characteristics curve is 0.823.
Conclusion: This study indicates that differential forms obtained from 3D data are very promising in characterizing melanoma. Combining these features with other skin features such as border irregularity and color variation might further improve the accuracy and reliability of the automatic diagnosis of melanoma.     

Digital image management project for dermatological health care environments: a new dedicated software and review of the literature

Background/purpose: Because the skin is the only organ completely accessible to visual examination, digital technology has therefore attracted the attention of dermatologists for documenting, monitoring, measuring and classifying morphological manifestations. To describe a digital image management system dedicated to dermatological health care environments and to compare it with other existing softwares for digital image storage.
Methods: We designed a reliable hardware structure that could ensure future scaling, because storage needs tend to grow exponentially. For the software, we chose a client-web server application based on a relational database and with a 'minimalist' user interface.
Results: We developed a software with a ready-made, adaptable index of skin pathologies. It facilitates classification by pathology, patient and visit, with an advanced search option allowing access to all images according to personalised criteria. The software also offers the possibility of comparing two or more digital images (follow-up). The fact that the archives of years of digital photos acquired and saved on PCs can easily be entered in the program distinguishes it from the others in the market. This option is fundamental for accessing all the photos taken in years of practice in the program without entering them one by one. The program is available to any user connected to the local Intranet and the system may directly be available in the future from the Internet.
Conclusions: All clinics and surgeries, especially those that rely on digital images, are obliged to keep up with technological advances. It is therefore hoped that our project will become a model for medical structures intending to rationalise digital and other data according to statutory requirements.     

Photoaging of the chest analyzed by capacitance imaging

Objective: Capacitance imaging is a new technique using sensors based on silicon technology developed to record fingerprints for security reasons. Applying such a sensor onto the skin surface gives the capacitance (hydration) map of the skin surface with a two-dimensional resolution of 50 μm. This method was used to characterize skin of the chests of 64 women with various grades of skin photoaging.
Method: The severity of photoaging of the chest skin of 64 women was clinically assessed according to a six-grade scale. Capacitance images of the skin were recorded and analyzed in terms of mean capacitance, homogeneity of gray levels and density of microrelief lines. Capacitance images of the adjacent unexposed area (upper part of the breast) were also recorded and analyzed for comparison. Pictures of the different areas were recorded.
Results: Microrelief line density decreases with the age of the volunteers but is independent of the severity of photoaging. Mean hydration of the skin surface is found to be independent of both photoaging severity and age. Evenness of hydration is a parameter markedly linked to the severity of photoaging independent of age. Uneven hydration is related to the juxtaposition of both hydrated and dry areas corresponding to some hyperpigmented and hyperkeratosic areas. Moreover, capacitance images reveal that some of the hyperpigmented areas may exhibit under- or over-hydrated conditions depending on the nature of the lesion.
Conclusion: Irregular skin surface hydration is an important characteristic of skin photoaging. It is related to skin pigmentation but does not parallel its unevenness of pigmentation.     

Geometrical capillary network analysis

Background: Skin microcirculation, especially the superficial network, can be assessed by a computer capillary video microscope system. The study of morphology and dynamics of microcirculation must include all dynamic and cooperative processes between the capillaries. For characterizing capillary ensembles, the statistical and geometrical properties of the network need to be explored.
Methods: The microvaculature of the skin and the microcirculation were investigated by combining videocapillaroscopy (VCP) and image processing techniques based on computational geometry and graph theory. Our goal was to characterize the capillary network in noisy pictures of the scalp. Different geometric methods were developed, based on proximity parameters (distance and surface) in order to circumscribe and construct this network.
Results: By studying the distribution of these parameters, extreme values or outliers, which usually correspond to artifact subregions in the pictures could be eliminated. Different algorithms were developed and has been implemented in an image processing software (Capilab Toolbox).
Conclusion: This computerized system is capable of real-time processings, increasing the quality of videocapillaroscope images and minimizing the disturbance of artifacts. The algorithms presented here are easy to implement and can process any kind of images of the skin, even in the scalp. In association with an example-based detection system, this method can be generalized to other stimuli in the same conditions.     

Visual attention to variation in female facial skin color distribution

Objectives  Visible skin condition of women is argued to influence human physical attraction. Recent research has shown that people are sensitive to variation in skin color distribution, and such variation affects visual perception of female facial attractiveness, healthiness, and age.
Methods  The eye gaze of 39 males and females, aged 13 to 45 years, was tracked while they viewed images of shape- and topography-standardized stimulus faces that varied only in terms of skin color distribution.
Results  The number of fixations and dwell time were significantly higher when viewing stimulus faces with the homogeneous skin color distribution of young people, compared with those of more elderly people. In accordance with recent research, facial stimuli with even skin tones were also judged to be younger and received higher attractiveness ratings. Finally, visual attention measures were negatively correlated with perceived age, but positively associated with attractiveness judgments.
Conclusions  Variation in visible skin color distribution (independent of facial form and skin surface topography) is able to selectively attract people's attention toward female faces, and this higher attention results in more positive statements about a woman's face.     

Capacitance imaging of the skin surface

BACKGROUND/AIMS: A new device allowing recording capacitance images of the skin surface was recently presented. Parameters, extracted from the gray-level histogram of the images, are tested for a new approach of skin surface hydration measurement in comparison with the classical capacitance method. Illustration of the interest of having both images and parameters for studying the homogeneity and the level of skin surface hydration are presented. METHODS: Software for selecting a region of interest from an image and measuring the parameters derived from its gray-level histogram was used to characterize skin hydration. RESULTS: There is a very close correlation between a Corneometer and the parameters extracted from the SkinChip measurements. The importance of having capacitance images of skin is demonstrated in case of non-homogeneity of the skin hydration, either because of photoaging or following an inflammation process. CONCLUSION: Capacitance imaging is a necessary tool for both completely describing and quantifying skin surface hydration.     

A new technique to in vivo study the corneocyte features at the surface of the skin

Purpose of the study: To design, develop and validate a new device allowing the features of corneocytes at the surface of the skin to be visualized in vivo and objectively characterized. Materials and methods: Monochromatic light is focused at the proximal end of a coherent bundle of optical fibres. Fluorescence of skin, stained with fluorescein, is then captured by the same fibre bundle and displayed, through a dichroic mirror, by a CCD camera. Fluorescence images are analysed using dedicated software to measure the projected area of cells. Results: The new device allows the mean projected area of corneocytes to be routinely studied and quantified on most of the skin areas of the human body. Measurements carried out on two age groups of women confirm that corneocyte size on the forearm is smaller in young women than in older women. Conclusion: The new non‐invasive device is easy to use and appear quite appropriate for cutaneous investigations carried out in clinical research.     

New approach to the evaluation of skin color of pigmentary lesions using Skin Tone Color Scale

Objective methods of measuring skin color are needed to evaluate pigmentary lesions quantitatively. We have developed a new method of measuring skin color using a plastic bar system called the Skin Tone Color Scale based on Munsell's color space system. We have also evaluated the effectiveness of various therapies using this measurement system. Our system was designed to measure skin color in normal skin, pigmentary lesions of solar lentigo, chloasma and ephelides, and postinflammatory pigmentation. Moreover, effectiveness of various therapies for these pigmentary lesions was evaluated. The evaluations made with this system were closely related to physician assessment. This method may be useful in measuring of skin color and evaluating the effectiveness of therapies for pigmentary diseases.     

Palpation of the skin with a robot finger: an attempt to measure skin stiffness with a probe loaded with a newly developed tactile vibration sensor and displacement sensor

Background/aims: Various attempts have been made to measure mechanical properties of the skin quantitatively and noninvasively. However, no attempt has been made to measure a tactile sense of our finger that palpates the skin; when we palpate the skin to search for any change, we at first rub the skin surface softly with a finger tip to detect a surface change and then press the finger against the skin to perceive any alteration in consistency. The problem here is how to record such tactile sense quantitatively, because the palpating examination for smoothness or softness of the skin totally depends on a subjective perception. A new tactile sensor from robot technology is equipped with a fingertip-like sensing probe oscillating at a resonant frequency of 60 kHz; it is capable of clearly sensing small differences in hardness of solid substances from a change in the oscillating frequency and from a displacement sensor that detects depressability of the skin. We have used this new measuring system to evaluate the hardness and elasticity of skin.
Methods: We constructed a probe with two independent sensors, i.e., a newly developed tactile vibration sensor and a displacement sensor. To determine its usefulness we first used an in vitro skin model and subsequently used normal and lesional skin, such as neutrophilic erythema, keloid, hypertrophic scar, and scleroderma.
Results: Two parameters were obtained with our probe: one that reflected superficial firmness of the skin, which mainly correlated with the hydration state of the stratum comeum, and the other that reflected the firmness of deeper tissue.
Conclusion: Our results showed that this probe is useful for evaluating the physical properties of skin lesions that accompany changes in skin firmness.     

Age-dependent changes in skin surface assessed by a novel two-dimensional image analysis

Background/purpose: Skin microrelief has been studied using various methods and devices. However, the long duration of time needed to process one sample or the expensive equipment hampered the use of those systems for routine diagnosis. Today, the emergence of new software and hardware technologies may allow this issue to be resolved.
Methods: To characterize objectively the skin surface, we introduced a new parameter SPm , namely, the area mean of superficial skin texture block formed by primary and secondary lines crossing each other. Based on the skin detector produced by the Boseview Technology Company, we developed a software for acquiring automatically skin images and calculating SPm . The relationship between SPm and age was studied on the dorsal and ventral midway of the forearm (sun-exposed and sun-protected areas) of 94 healthy volunteers without a history of smoking.
Results: The skin surface topography can be conveniently quantified with the new parameter SPm . The value of SPm of both sites increases with age, independent of sex, with the site more exposed to light being more affected.
Conclusion: With the software developed, the details of the skin surface can be observed. SPm appears to be a new valid parameter for characterizing the property of the skin surface. Our method, alone or in combination with other technologies of skin topography analysis may be applied in routine diagnosis for a quantified evaluation of skin aging.     

Computer recognition of skin structures using discriminant and cluster analysis

Background/aims: Automated image analysis of complex tissues is usually limited by the difficulty of recognizing special structures by computer. The aim of this study was to test the applicability of discriminant and cluster analysis to the interpretation of skin images.
Methods: Digital images from microscopic, dermatoscopic and clinical views of skin specimens were electronically dissected into elements of equal size and shape, and a set of grey level, colour and texture features was assessed for each element. Elements were classified interactively and submitted to discriminant analysis. Furthermore, hierarchical cluster analysis was used to enable the system to classify the tissue elements automatically, based on the available digital information. The classification results were relocated to the original image in order to evaluate the performance of the procedure.
Results: The system performs well in reproducibly detecting different skin structures in digital images. Discriminant analysis of interactively classified elements yielded a correct reclassification in 98 to 100% of tissue elements. Among the cluster analysis procedures, the conservative Ward method after removal of all highly correlated features produced the best results. The method turned out to be applicable irrespective of the image source used.
Conclusions: Discriminant and cluster analysis may be helpful techniques for a user-independent, subjectively unbiased measurement system of skin structures.