Analysis of spectroscopic diffuse reflectance plots for different skin conditions (original) (raw)
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Review of current techniques to analyze diffuse reflectance spectra for diagnosis of skin lesions
AIP Conference Proceedings, 2008
Determination of tissue optical properties across of diffuse reflectance spectroscopy is an effective and extensively used technique for the non-invasive study of tissues. The methods to obtain the spectra are practically uniform, however, approaches for signal detection and data processing have varied widely. In some cases it is used a physical model (Monte Carlo model, the diffusion approximation to the transport equation), in other cases an empiric model (principal component analysis) accompanied by tools (Support Vector Machine, Neural Network, Partial Least Squares, etc.) that allow to analyze the obtained spectra. In this work, we present a critical review of the available methods used to analyze the measured diffuse reflection spectra of human skin for diagnostic purposes.
Optics and Photonics Journal
In this study, we focused on diffuse reflectance spectroscopy, a rapid and noninvasive spectroscopy technique that has considerable potential for medical diagnosis. In order to better understand and analyze the signals induced by this method, we performed a series of in vivo measurements on healthy and diseased skin. Measurement sites on a human hand and feet were chosen. Some preliminary results obtained on these sites show the feasibility of this technique in clinics.
Journal of Biomedical Optics, 2006
Differences in absorption and/or scattering of cancerous and normal skin have the potential to provide a basis for noninvasive cancer detection. In this study, we have determined and compared the in vitro optical properties of human epidermis, dermis, and subcutaneous fat with those of nonmelanoma skin cancers in the spectral range from 370 to 1600 nm. Fresh specimens of normal and cancerous human skin were obtained from surgeries. The samples were rinsed in saline solution and sectioned. Diffuse reflectance and total transmittance were measured using an integrating sphere spectrophotometer. Absorption and reduced scattering coefficients were calculated from the measured quantities using an inverse Monte Carlo technique. The differences between optical properties of each normal tissue-cancer pair were statistically analyzed. The results indicate that there are significant differences in the scattering of cancerous and healthy tissues in the spectral range from 1050 to 1400 nm. In this spectral region, the scattering of cancerous lesions is consistently lower than that of normal tissues, whereas absorption does not differ significantly, with the exception of nodular basal cell carcinomas ͑BCC͒. Nodular BCCs exhibit significantly lower absorption as compared to normal skin. Therefore, the spectral range between 1050 and 1400 nm appears to be optimal for nonmelanoma skin cancer detection.
Validation of tissue optical properties measurement using diffuse reflectance spectroscopy (DRS)
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVIII
The effectiveness of photodynamic treatment depends on several factors including an accurate knowledge of optical properties of the tissue to be treated. Transmittance and diffuse reflectance spectroscopic techniques are commonly used to determine tissue optical properties. Although transmittance spectroscopy technique is accurate in determining tissue optical properties, it is only valid in an infinite medium and can only be used for interstitial measurements. Diffuse reflectance spectroscopy, on the other hand, is easily adapted to most tissue geometries including skin measurements that involve semi-infinte medium. However, the accuracy of the measured optical properties can be affected by uncertainty in the measurements themselves and/or due to the uncertainty in the fitting algorithm. In this study, we evaluate the accuracy of optical properties determination using diffuse reflectance spectroscopy implemented using a contact probe setup. We characterized the error of the optical properties fitted using two fitting algorithms, a wavelength wise fitting algorithm and a full reflectance spectral fitting algorithm. By conducting systematic investigation of the measurements and fitting algorithm of DRS, we gained an understanding of the uncertainties in the measured optical properties and outlined improvement measures to minimize these errors.
Physiological basis for noninvasive skin cancer diagnosis using diffuse reflectance spectroscopy
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.
Polish Journal of Medical Physics and Engineering
Today, to establish a diagnosis, the patient must undergo a biopsy followed by histopathological diagnosis, which causes unnecessary cost, patient trauma, and time delay to obtain a diagnosis. However, the metastases can be discovered by diffuse reflectance spectroscopy, which is a simple method that investigates the light distribution within tissue. The theme of this paper is the use of diffuse reflectance spectroscopy (DRS) to determine the optical spectrum of hamster specimen’s tissue and to differentiate biological changes due to laser irradiation (scattering, and cell changes) under the skin. DRS measurements were made on healthy and malignant tissue to diagnose the stages of cancer formation using a fiber-optic probe. The results show that malignant tissue is characterized by a significant decrease in diffuse reflectance spectrum compared to normal tissue.
Exploratory multivariate spectroscopic study on human skin
Skin Research and Technology, 2003
Background/aims: Spectroscopy on human skin is a field that is being adopted increasingly because of its rapidity and high reproducibility. Infrared reflectance (IR), near-infrared reflectance (NIR), and fluorescence spectroscopy have previously been applied to human skin in vivo to compare healthy and sick skin, including skin cancer, atopy, and leprosy. Exploratory data analysis/chemometrics is a tool for evaluating multivariate data such as spectroscopic measurements. The objective of this study was to explore the spectral variance spanned by people with normal integument, and to demonstrate the advantages of multivariate analysis to skin research. Methods: IR, NIR and fluorescence spectroscopy have been carried out in vivo on 216 volunteers' forearms before and after four tape strippings. The subjects were asked to fill in a questionnaire regarding factors suspected to influence the measurement results. Principal Component Analysis (PCA) was used to investigate whether the population can be divided into groups on the basis of their skin chemistry. Unless otherwise stated, the results are from the measurements prior to stripping. Results: In contrast to IR and fluorescence spectra, NIR spectra proved able to detect gender differences. By use of PCA, classifications on male and female subjects were observed from the IR and NIR measurements, and as an indication from the fluorescence measurements. The NIR and fluorescence measurements varied between elderly and young subjects. The largest variance in the fluorescence landscapes was seen between pigmented and non-pigmented skin. No connection was found between the spectroscopic measurements and smoking or drinking habits. Conclusions: Future spectroscopic skin investigations should be balanced as regards to gender and age, as these can possibly affect the measurement results. Chemometrics proved to be superior to traditional attempts of interpreting the spectra.
Spectral imaging of skin: experimental observations and analyses
Medical Imaging 2006: Physics of Medical Imaging, 2006
The emergence of compact optical spectral imaging technologies has motivated the study of their use in a variety of applications, including medical diagnosis and monitoring. In particular, large format CCD focal planes in conjunction with spectrally tunable devices offer enhanced spatial information together with visible and near infrared (NIR) spectroscopic data for the passive, noninvasive, measurement of human skin and near surface tissue characteristics. One such spectral imaging system was recently developed by mating a Liquid Crystal Tunable Filter (LCTF) together with a 2048x2048 silicon CCD focal plane. This system is capable of collecting more than 30 co-registered spectral images spaced every 10 nanometers and spanning 400 to 720 nanometers. This system combines the potential of near infrared diffuse reflectance spectroscopy with the high spatial resolution of traditional optical imaging techniques. Spectral images were acquired of portions of the hands and arms of several test subjects with a variety of features observable. The observations were collected in a "light box" under controlled illumination conditions. Images of a diffuse reflectance standard and instrument dark frames were collected to allow conversion of the raw images to spectral reflectance images. This paper presents examples of the spectral images collected, instrument characteristics and performance, and results of analysis algorithms applied to the data. Results also are shown for a new algorithm extracting the saturated oxygen hemoglobin fraction from these data.
British Journal of Dermatology, 2008
Various physical, chemical and biological insults, including exposure to ultraviolet (UV) radiation, cause erythema and change in pigmentation in human skin. These reactions provide an important measure of the cutaneous response to the insult. To present a new implementation of a method for objective in vivo measurement of erythema and pigmentation. The method is based on acquisition of reflectance spectra in the visible range using a commercially available spectrophotometer. The probe of this instrument incorporates an integrating sphere that captures the light remitted from the skin in a wide range of angles. We corrected the acquired reflectance spectra for the contribution of specular reflections by an amount given by the Fresnel equation and verified this correction experimentally. This correction is particularly important when measurements are performed on heavily pigmented skin. The corrected reflectance spectra are then transformed into absorbance spectra. To analyse these spectra, we developed an algorithm which can be used to calculate apparent concentrations of oxyhaemoglobin, deoxyhaemoglobin and melanin. This method was tested in clinical studies of skin reactions induced by exposure to UV radiation. These experiments involved three groups of subjects with progressively darker complexion (constitutive pigmentation). Each group consisted of 10 subjects. Erythema was measured 1 day after UV exposure, and pigmentation (melanin content) 1 week later. Results Distinct apparent absorbance spectra were obtained for dark, intermediate and fair skin. There was good agreement between reconstructed spectra and experimental data at relevant wavelengths. Difference absorption spectra were able to show the dose dependence of UV-induced responses, and erythema and pigmentation values obtained by the spectroscopic method showed good correlation with those derived by subjective visual grading. The results demonstrate that the presented methodology provides an objective noninvasive way of measuring UV-induced reactions independently of the level of constitutive pigmentation.