In this study, we present two methods for estimation of &pbeta;-carotene content in flour with use of color analysis of the flour samples. One method is based on the fact that the color parameter "chroma" (the color saturation) in the CIE1976 (L*a*b*) - system can be used as the "yellowness index" of the flour that is proportional to &pbeta;-carotene content in the flour. Another method is based on comparison of the flour diffuse reflection coefficients at 460 nm (absorption band of &pbeta;-carotene) and 650 nm. The value of contrast of absorption band manifestation can be also used as the "yellowness index" of the flour.
A simple polarization method for characterization of anisotropic scattering media is considered. Two sets of independent empirical characteristics entirely representing scattering properties of an examined specimen in the experimental geometry used are specified. Experimental examples showing the possibilities of the method are presented.
Based on the presented two-layer eye iris model, the iris diffuse reflectance has been calculated by Monte Carlo
technique in the spectral range 400-800 nm. The diffuse reflectance spectra have been recalculated in L*a*b* color
coordinate system. Obtained results demonstrated that the iris color coordinates (hue and chroma) can be used for
estimation of melanin content in the range of small melanin concentrations, i.e. for estimation of melanin content in blue
and green eyes.
Based on the experimental data obtained in vivo from digital analysis of color images of human irises, the mean melanin
content in human eye irises has been estimated. For registration of the color images a digital camera Olympus C-5060
has been used. The images have been obtained from irises of healthy volunteers as well as from irises of patients with
open-angle glaucoma. The computer program has been developed for digital analysis of the images. The result has been
useful for development of novel and optimization of already existing methods of non-invasive glaucoma diagnostics.
Based on the experimental data obtained in vivo from digital analysis of color images of human irises, the mean melanin
content in human eye irises has been estimated. For registration of the color images a digital camera Olympus C-5060
has been used. The images have been obtained from irises of healthy volunteers as well as from irises of patients with
open-angle glaucoma. The computer program has been developed for digital analysis of the images. The result has been
useful for development of novel and optimization of already existing methods of non-invasive glaucoma diagnostics.
We present experimental results on optical properties of the human skin controlled by administration ofthe 40%-glucose
solution. In vivo reflectance spectra of the human skin were measured. Results of the experimental study of influence of
the 40%-glucose solution on reflectance spectra of the human skin are presented. A significant decrease of reflectance of
the human skin under action of the osmotic agent is demonstrated. The experiments show that administration of the
glucose solution allows for effective control of tissue optical characteristics, that makes skin more transparent, thereby
increasing the ability of light penetration through the tissue. Laser Doppler flowmetry has been used for study of skin
blood microcirculation under the action of the glucose solution. Results of the experiments demonstrated that at the
action of the glucose solution blood perfusion and blood concentration increase, however the mean blood velocity does
not change. The presented results can be used in developing functional imaging techniques, including OCT and
reflectance spectroscopy. A potential benefit of the optical clearing technique is the improvement of laser therapeutic
techniques that rely on sufficient light penetration to a target embedded in tissue.
The reconstruction method of the human skin intrinsic fluorescence spectra distorted by "the screen effect" was proposed. The method is based on the fact that fluorescence and reflectance spectra are formed by the same absorption and scattering properties of the media. Therefore diffuse reflectance spectrum can be used for fluorescence spectrum reconstruction. The intrinsic fluorescence spectral profiles restoration was tested experimentally using scattering media (phantoms, solutions) with a fluorescent dye and hemoglobin as a strong absorber producing inner-filter distortions. The correction produces the fluorescence spectrum profiles same to the one measured from the corresponding sample with an infinitely low absorption. In this paper we present the results of the fluorescence spectra reconstruction using coefficient &sqrt;Rd(λ) as a correction factor.
Based on the experimental data obtained in vivo from digital analysis of color images of human irises, the mean melanin content in human eye irises has been estimated. For registration of the color images a digital camera Olympus C-5060 has been used. The images have been obtained from irises of healthy volunteers as well as from irises of patients with open-angle glaucoma. The computer program has been developed for digital analysis of the images. The result has been useful for development of novel and optimization of already existing methods of non-invasive glaucoma diagnostics.
The results of experimental study of influence of macroscopic optical anisotropy and scattering properties of tissue
samples on their optical polarization characteristics, which can be measured in simple polarirnetric experiment, are
presented. In-vitro samples of animal tissue (rat skin) were examined in these experiments. The experimental technique
used is based on the detection of the intensities of the co- and cross-polarized components of the light transmitted
through the scattered medium, which is rotated between two polarizes. It is shown that the whole rat skin has
macroscopic optical birefringence with the average difference ofrefractive indices Δn ~ 0.00024.
The results of an experimental study of the possibilities of monitoring erbium yttrium aluminum garnet laser-mediated ablation of human epidermis with the use of Fourier transform infrared (FTIR) spectroscopy and spectral polarization techniques are presented. The attenuated total reflection (ATR) method was used for FTIR spectroscopic measurements. Spectral polarization monitoring of the ablation was carried out by analyzing the spectra of the degree of residual linear polarization of a probe light diffusely reflected from the laser-treated region of skin. It was found that the analysis of FTIR spectra allows monitoring of the water and protein contents in the subsurface layers of the treated skin, while the degree of residual polarization measured at the wavelengths of maximal absorption of hemoglobin is sensitive to changes in the epidermis thickness and the blood content in the dermal layer (the degree of erythema).
We report a new method for quantitative analysis of erythema and pigmentation of the human skin using of the skin surface image. The erythema and pigmentation indices as well as the polarization degree of backscattered light are applied as the visualization parameters. The comparative analysis of the quality of various types of images is performed. Quality of reconstructed images was estimated in terms of image contrast. It is shown that the skin image contrast for the case of the erythema index as visualization parameter as well as the image contrast for the case of the pigmentation index as visualization parameter exceed at least in three times the similar values for the conventional color image or R, G, B image components. Maximum value of the contrast can be achieved in the case of using the polarization degree as the visualization parameter. The reported method of skin imaging can be used as an objective tool for diagnostics of the skin diseases.
The method of scattering media probing with the use of low-coherent light source with the controllable width of emission spectrum is considered. The contrast of partially coherent speckles is suggested as the diagnostical parameter. The additional polarization discrimination of detected speckles gives the possibility to select the components of scattered field which propagate in probed medium at different distances. Experimental results obtained for weakly ordered systems characterized by non-diffuse scattering regimes are presented.
The set of topically united practical works on in vivo reflectance and fluorescence spectroscopy of the human skin of the special training laboratory on optical biophysics for the undergraduate and postgraduate students specialized in biophysics, biochemical physics and medical physics is described.
Polarization imaging of superficial layers of multiply scattering medium with selective localized absorber is discussed. This method is based on the analysis of polarization spectra of backscattered partially polarized light. The polarization spectra of a backscattered light are studied for phantom scattering media and for in vivo tissues. The relations between media scattering properties, the depth of absorber location, and the polarization degree as well as polarization difference reflectance spectra are discussed. It is shown that polarization degree spectra and apparent optical density spectra have the similar behavior. The depth of location of absorbing object may be evaluated by use of analysis of polarization difference reflectance spectra. This analysis can be provided on the basis of the concept of polarization decay in scattering media.
Comparative analysis of manifestation of finite absorption in scattering media is carried out for different detection geometries. Reflectance spectra were studied for phantom scattering media containing blood and melanin as absorbers. Apparent optical density spectra of phantom media are compared with similar spectra of water solutions of the blood and melanin for same concentrations of absorbers. The influence of scattering properties on optical density spectra is discussed with use of the model of diffuse light propagation in semi-infinite media.
The set of topically united practical works on coherent optics of scattering media dn interferometry of random phase objects of the special training laboratory on optical biophysics for the undergraduate and postgraduate students specialized in biophysics, biochemical physics and medical physics is described. Presented materials were also discussed on SPIE's 7th International Conference on Education and Training in Optics and Photonics 2001, 26-30 November, 2001.
We present experimental results on the in vitro and in vivo
study of dye diffusion into human skin and hair follicles. We have
studied some commercially available dyes for potential using in the
laser selective thermolysis. The degree and the depth of hair follicle
dyeing inside the skin were determined. For hairs in different stages
the sebaceous gland was stated as a reservoir for a dye administration.
It was found that the penetration depth of dyes is about 1.2 mm from
the skin surface. We have developed the biocompatible Indocyanine
Green lotions and the method for in vivo dyeing and dye in depth
monitoring. Shift on 16–21 nm of absorption peak of Indocyanine
Green to the longer wavelengths due to Indocyanine Green binding
with cell proteins in the human skin was found.
We have presented experimental data on in vivo and in vitro study on the optical clearing of the scleral tissue controlled by administration of the osmotic liquids. For example, administration of glucose induces matter diffusion and as a result equalization of the refractive indices of scleral tissue scatterers and interstitial fluid. The significant increase of transmittance and decrease of reflectance of the sclera under glucose solution action have been demonstrated. The glucose diffusion coefficient has been estimated. The results of in vitro study of polarization features of scleral optical transmittance at tissue clearing are also presented.
We present experimental results on optical properties of the rat skin controlled by administration of osmotic chemical, such as glycerol. Administration of glycerol induces matter diffusion and as a result equalization of the refractive indices of skin scatterers and interstitial fluid. The significant increase of the skin sample transmittance under action of glycerol has been demonstrated. The mean value of the glycerol diffusion coefficient has been estimated as(formula available in paper).
Study of influence of an absorption of scattering media on the residual polarization of backscattered linearly polarized light is carried out. Approximate expression describing dependence of the degree of residual linear polarization on optical properties of disordered media is obtained. Phenomenological theory of multiple scattered field formation due to superposition of partial components with different optical paths in multiply scattering medium and previously described similarity of various statistical moments of multiply scattered optical fields are used to estimate the degree of residual polarization. Suppression of partial components with large values of optical paths causes increase of this parameter for detected backscattered light. This effect is observed at the wavelengths of selective absorption of disordered media. Experimental results obtained for phantom scattering samples such as milk and in- vivo biological tissue (human skin) are presented.
On the basis of the Bragg diffraction model of coherent- optical interaction of laser radiation with ultrasonic wave, the influence of ultrasound axis position and ultrasound frequency value on the amplitude characteristics of ac photodetector current at the ultrasound frequency was theoretically analyzed. For intermediate scattering regime where the ballistic and low-step scattered light components are comparable in their values, the images of the absorbing squares were reconstructed on the base of the ac current amplitude at 3 MHz frequency and dc current distributions. The possibilities of the acousto-optical imaging of scattering medium were discussed on the basis of the results obtained after comparison with traditional measurements of dc photocurrent distributions.
A special training laboratory on optical biophysics for the undergraduate and postgraduate students specialized in biophysics, biochemical physics and medical physics in the framework of sub-specialties on biomedical optics, laser medicine, information technologies and mathematical modeling in medicine, and biomedical transducers and sensors is described. The laboratory consists of several sets of topically united practical works: (1) Electronics; (2) Coherent optics of scattering media and interferometry of random phase objects; (3) Coherent-domain optical methods in bio-medicine; (4) In vivo reflectance and fluorescence spectroscopy of human skin; (5) Educational-research setups for postgraduate students; (6) Tissue optics and spectroscopy.
Experimental results on in vivo and in vitro immersion clearing dynamics of the skin under action of the osmotic agent are presented. The significant decrease of the human skin reflectance in vivo under action of glucose solution is demonstrated. In vitro experiments with dyed immersion agents have shown that the immersion mostly penetrates into skin tissue though the dermal layer. Diffusion of the immersion agent through the stratum corneum barrier was insignificant. It was shown the hypodermic injection of the immersion agent is an effective way for the agent administration. The time-dependent contrast of the blood perfused areas in the cleared skin was estimated. The diffusion coefficient of 40%-glucose solution in skin in vivo was estimated as D equals (2.56+/- 0.13)(DOT)10-6cm2sec.
Theoretical and in vitro and in vivo experimental study of spectral and polarization characteristics of the human and rabbit eye tissues are presented. The possibility of control of optical properties of eye cornea, lens and sclera is discussed and realized experimentally for glucose solution as the refractive index matching factor.
On the basis of the suggested model of coherent-optical interaction of laser radiation with ultrasonic wave, the influence of geometry of experiment on the amplitude and phase characteristics of ac photo-detector current at the ultrasound frequency was experimentally and theoretically analyzed. For intermediate scattering regime where the ballistic and low-step scattered light components are measurable their contributions to ac photocurrent were separated by experimental data processing. With a use of theoretically predicted and experimentally confirmed optimal conditions of the measurement, the images of the absorbing half-plane were reconstructed in weak scattering media with use of the distributions of the ac amplitude of the current at 3 MHz ultrasound frequency and dc current. The possibilities of the acousto-optical imaging of multiply scattering medium were discussed on the basis of the results obtained after comparison with traditional measurements of dc photocurrent distributions.
Existence of non-zero residual polarization in case of backscattering of linearly polarized coherent light from semi-infinite disordered half-space is considered. This effect is caused by the significant contribution of the low- step scattered components for the backscattering mode and can be described phenomenologically by using the concept of distribution of effective optical paths of scattered light partial components. Influence of effective optical path statistics on the residual polarization degree was studied in the experiments with various phantom multiply scattering media. Corresponding results are presented.
Method of polarization visualization of superficial layers of multiply scattering medium containing macroinhomogeneities based on the analysis of polarization patterns of a backscattered linearly polarized light is discussed. The polarization properties of a backscattered light were studied for phantom scattering media (diluted milk with low concentrations). The influence of media scattering properties on inhomogeneity image is obtained by use of polarization degree and normalized scattered intensity as visualization parameters is discussed. Quality of reconstructed images was estimated in terms of spatial resolution and image contrast. Depth resolution of the considered polarization imaging in the backscattering mode is discussed. Phenomenological description of the polarization image formation is carried out by means of the concept of statistical distribution of effective optical paths of partial components of scattered optical field.
Ultrasound modulation of scattered laser light was studied to develop the technique of acoustooptical visualization of the objects imbedded in scattering media. The focused ultrasound wave intersected the laser radiation in a medium. They passed through the medium laser light was collected by a photo-detector. The ac current characterized the optical properties of the zone of intersection of laser and sound beams. On the basis of the suggested model of coherent- optical interaction of laser radiation with ultrasonic wave, the expression for ac current was derived taking account of finite size of the laser beam diameter and the Gaussian distribution of the laser beam intensity, when the Bragg angle was much less than 1. The influence of medium scattering properties and geometry of experiment on the ac photo-detector current and signal to noise ratio was analyzed. With a use of theoretically predicted and experimentally confirmed results, the images of the absorbing half-plane using distributions of the ac amplitude of the current at 3 MHz ultrasound frequency and dc signal were reconstructed in weak scattering media. The possibilities of the acoustooptical imaging were discussed on the basis of the results obtained after comparison with traditional measurements of dc photocurrent distributions.
Method of polarization visualization of superficial layers of multiply scattering medium containing macroinhomogeneities based on the analysis of polarization patterns of a backscattered linearly polarized light is discussed. The polarization properties of a backscattered light were studied for phantom scattering media (diluted milk with low concentrations). The influence of media scattering properties on inhomogeneity image obtained by use of the polarization degree and normalized scattered intensity as visualization parameters is discussed. Quality of reconstructed images was estimated in terms of spatial resolution and image contrast. Depth resolution of the considered polarization imaging in the backscattering mode is discussed. Phenomenological description of the polarization image formation is carried out by means of the concept of statistical distribution of effective optical paths of partial components of scattered optical field. Some peculiarities of the polarization characteristics of backward multiply scattered light, which influence on the polarization images formation, are discussed.
We presented RGB video microscopic system for in vitro monitoring of optical properties of hair shaft and follicle and experimental results of study of the hair optical and geometrical properties using RGB analysis techniques.
We describe the fabrication, characterization and possible application of a new type of optical material -- a 2- dimensional air-glass photonic crystal.
We present experimental results on optical properties of the rat skin controlled by administration of osmotically active chemical, such as the 40%-glucose solution. In vivo reflectance and in vitro transmittance spectra of the rat skin were measured. Result of the experimental study of influence of the 40%-glucose solution on reflectance and transmittance spectra of the rat skin are presented. The significant increase of transmittance and decrease of reflectance of the rat skin under action of osmotical agent are demonstrated. The average value of glucose solution diffusion coefficient was estimated as 1.101(DOT)10-6+/- 0.153(DOT)10-6 cm2/sec.
We present experimental results on in vitro and in vivo investigation of dye diffusion into the human skin and hair follicles. It was shown that dyeing as a method of enhancement of the absorption coefficient of hair follicle tissue components can be used for selective photodestruction of hair follicle and surrounding tissues. Strength and depth of hair follicle dyeing inside the skin were determined for various dyes.
We present experimental results and computer modeling of investigation on the optical properties of the human dura mater controlled by administration of osmotically active chemical, such as mannitol and glucose solutions with various concentrations. Administration of chemical agent induces diffusion of matter and as a result equalization of the refractive indices of collagen and ground material. Results of experimental study of influence of osmotical liquids (mannitol and glucose solutions) on reflectance and transmittance spectra of the human dura mater are presented. The significant decreasing of the reflectance and increasing of the transmittance of the human dura mater samples under action of osmotical solutions were demonstrated.
We present experimental results on optical properties of the rat skin controlled by administration of osmotically active chemical, such as glycerol. In vivo reflectance and in vitro reflectance and transmittance spectra of the rat skin were measured. Results of experimental study of influence of glycerol on reflectance spectra of the rat skin are presented. The significant increase of transmittance and decrease of reflectance of the rat skin under action of osmotical agent are demonstrated. Basing on mathematical modeling the optical parameters of the rat skin are determined.
Different techniques for diagnostics and visualization of the inhomogeneous scattering media by means of the statistical analysis of spatial-temporal fluctuations of scattered light are considered: (1) polarization diagnostics and imaging based on the application of the polarization degree as visualization parameter; (2) imaging techniques on the basis of measurements of the contrast of multiply scattered speckles induced by partially coherent light scattering in the probed object; (3) modification of the speckle imaging technique based on the statistical analysis of time-integrated electronic images of the speckle patterns under coherent light illumination. Comparison of these methods with traditional approaches to the diagnostics and imaging of macroscopically inhomogeneous multiply scattering objects is made. Experimental results obtained with phantom scattering media and illustrating the potentialities of the discussed approaches are presented.
Basing on such fundamental optical phenomena as elastic and quasi-elastic light scattering, diffraction, and interference of optical fields we have designed coherent optical methods offering much promise for biomedical applications. The scope of research includes the development of photon-correlation spectroscopy, speckle-interferometry, coherent micro-topography of living tissues, and study of optical images contrasting due to reduction of scattering properties of surrounding medium using immersion liquids.
Different techniques for diagnostics and visualization of the inhomogeneous scattering media by means of the statistical analysis of spatial-temporal fluctuations of scattered light are considered: (1) polarization diagnostics and imaging based on the application of the polarization degree as visualization parameter; (2) imaging techniques on the basis of measurements of the contrast of multiply scattered speckles induced by partially coherent light scattering in the probed object; (3) modification of the speckle imaging technique based on the statistical analysis of time-integrated electronic images of the speckle patterns under coherent light illumination. Comparison of these methods with traditional approaches to the diagnostics and imaging of macroscopically inhomogeneous multiply scattering objects is made. Experimental results obtained with phantom scattering media and illustrating the potentialities of the discussed approaches are presented.
Results of experimental and theoretical study of the optical properties of the eye sclera controlled by administration of osmotically active chemical, such as glucose, are presented. Glucose administration induces the diffusion of matter and as a result the equalization of the refractive indices of collagen fibrils and base material, and corresponding changes of transmittance spectra of scleral tissue. Transmittance spectra of the human scleral samples impregnated by glucose were measured. The significant increase of transmittance under action of osmotic liquid was observed. The diffusion coefficient of glucose within scleral tissue was estimated; the average value is 3.45 X 10-6 +/- 4.59 X 10-7 cm2/sec. The results are general and can be used to describe many other fibrous tissues impregnated by osmotically active chemical agents.
The diffusion of glucose with various concentrations through human sclera and cerebral membrane in vitro was studied. The dynamics of this process was monitored by time-dependent weight and optical measurements. Glucose administration induces the diffusion of matter and as a reslut the equalization of the refractive indices of collagen fibrils and ground material, and corresponding changes of transmittance spectra of fibrous tissue. Transmittance spectra of the human scleral and cerebral membrane samples impregnated by glucose were measured. Investigation of diffusion process in scleral samples, previously dried and swelled in distillated water was performed. Experimental results are presented.
The theoretical analyze of coherent acousto-optical interaction in the turbid medium resulting in the appearance of ultrasound modulation of the photo-detector current has been fulfilled. Analysis of the influence of tissue scattering properties and geometry of experiment on spatial resolution of technique of acousto-optical imaging by using of considered model is made. The relations between amplitude and phase of the ac current and the receiver system parameters are derived. The optimal conditions for measurements of the ac current on ultrasound frequency are determined. The experimental testing of these conditions have been accomplished with focused ultrasound wave at 3 MHz. The noise characteristics of detection system were studied as well.
Experimental results on the optical properties of the human eye sclera controlled by administration of osmotically active chemicals, such as propylene glycol and glucose are presented. Administration of chemical agents induces diffusion of matter and as a result equalization of the refractive indices of collagen and ground material. Experimental study of influence of propylene glycol and glucose on reflectance and transmittance spectra of human eye sclera was performed. In vitro diffusion reflectance spectra of the whole human eye and transmittance spectra of the sclera samples were investigated. In vivo measurements were fulfilled on a rabbit eyes. The significant increase of transmittance and decrease of reflectance of human eye sclera and rabbit eye under action of osmolytic liquids was demonstrated. The matter diffusion coefficient for the scleral samples impregnated by glucose solution was estimated; the average value is 1.27x10-5 ± 2.26x10-6 cm2/sec. The results are general and can be used to describe many other fibrous tissues.
Simple optical model of three-layer fluorescent phantom of biotissue with optically thick lowest layer was proposed. In the series of samples with varied 'epithelium' thickness and 'stromal' blood content the tendencies predicted by the model were observed.
Technique of polarization imaging of multiple scattering tissues which contain the embedded large-scale inhomogeneous is discussed. This method is based on the measurements of the spatial distribution of the polarization degree of light scattered by tissue under study. Analysis of the influence of tissue scattering properties and geometry of experiment on the contrast and spatial resolution of reconstructed images by using the concept of optical paths distribution for partial components of scattered field is made. Interrelation between forms of spatial distributions of polarization degree and intensity distributions is discussed on the basis of theoretical analysis and experimental results obtained with model objects. Possibilities of the increase of contrast of reconstructed image as well as the restrictions of this technique are discussed.
Experimental study and computer simulation were used to analyze tissue optics during a process of optical clearing due to refractive index matching. Tissue samples of the human and bovine sclera and the collagen sponge as a phantom were investigated. Osmotically active solutions, such as verografin and propylene glycol, were used as chemicals. A characteristic time response of human scleral optical clearing in the range 1 to 20 min was determined. The matter diffusion coefficient for the scleral samples to impregnated by verografin solution were experimentally estimated; the average value is 1.27 (DOT) 10-5 +/- 3.77 (DOT) 10-6 cm2/sec. The results are general and can be used to describe many other fibrous tissues.
When spectrofluorimetry is applied to the problem of diagnosis, correlation techniques relating spectral features to biotissue status should be used. But the coefficients of correlation equation should account for the relationship of spectral parameters with biochemical and morphological changes associated with the pathology. As a search for these dependencies in actual biotissue is difficult, we offer to employ tissue phantoms -- the physical models mimicking, under conditions of measurement, optical characteristics of the natural object. To model human cervix tissue, we used a three- layer planar structure, with upper 0.3 - 1.0 mm layer simulating epithelium, middle 0.03 - 0.1 mm layer representing basal membrane, and greater than 1.0 mm lower layer modeling subepithelial tissue. As a mechanical base of the structure we used 10% (per weight) gelatin gel. To simulate light scattering by biotissue, the nonabsorbing and nonluminiscent scatters were added to the upper and lower layers. NADH, FAD, and Protoporphyrin IX were added to upper layer. Collagen, as dried thin gelatin film, modeled basal membrane. To reproduce modulation of autofluorescence spectrum by reabsorption within the tissue, we added solution of human hemoglobin to the lower layer. Spectrofluorimetric measurement was performed using various excitation wavelengths (337 nm, 365 plus or minus 20 nm, and 405 plus or minus 20 nm).
Analysis of reflectance and autofluorescence spectra of in vivo human skin with eruthema was done. Monte Carlo simulation was used to model the tissue R and AF measurements. As a result the information about qualitative and quantitative changes of the main human skin chromophores, such as hemoglobin and melanin are, distribution within the skin tissue during the process of UV irradiation of the skin was obtained. The metabolic nature of investigated nonlinear process of UV radiation influence on the skin tissue can call interest as a problem of nonlinear dynamics.
The most frequently used techniques in the human skin diagnostics are reflectance and fluorescence spectroscopy. Technique of chromametry is based on color perception of the reflected from the skin white light. In CIE1976 (L*a*b*) color space the quantity estimation of color-difference between different states of the human skin have been defined by changes in parameters of brightness, hue and chroma of reflected light. This report focuses on the use of the perception of the color difference between autofluorescence of the human skin under different conditions for the purpose of skin diagnostics.
The methods available for testing the efficacy of topical sunscreens have improved considerably in recent years. Nevertheless, so far no simple and rapid test has been proposed to measure in vivo transmission spectra of sunscreens in the UVA region. Spectral changes that occur after sunscreen application were measured with a fluorescence spectrometer (LS 50B, Perkin Elmer, UK) equipped with a Y-shape quartz guide for in vivo measurements. Three sunscreens with different protection factors in the UVA range were tested. The excitation-emission maps of human collagen, skin, and sunscreens were analyzed. Visual demonstrations of the protective effects of sunscreens were also performed with photo- and video imaging techniques. As a consequence of the human skin and sunscreen's fluorescence map analysis, the optimal spectral regions (both for direct and indirect fluorescence measurements) were detected. In vivo fluorescence and remittance spectroscopy were used to investigate the time dependence in transmission spectra of epidermis with applied sunscreens. We also evaluate the feasibility of in vivo fluorescence measurements for the investigation of the sunscreen's water-resistance. The procedure is simple, and values obtained can be used to predict UVA protection on the basis of the mathematical algorithms.
Reflectance and fluorescence spectroscopy are successfully used for skin disease diagnostics. Human skin optical parameters are defined by its turbid, scattering properties with nonuniform absorption and fluorescence chromophores distribution, its multilayered structure, and variability under different physiological and pathological conditions. Theoretical modeling of light propagation in skin could improve the understanding of these condition and may be useful in the interpretation of in vivo reflectance and autofluorescence (AF) spectra. Laser application in medical optical tomography, tissue spectroscopy, and phototherapy stimulates the development of optical and mathematical light-tissue interaction models allowing to account the specific features of laser beam and tissue inhomogeneities. This paper presents the version of a Monte Carlo method for simulating of optical radiation propagation in biotissue and highly scattering media, allowing for 3D geometry of a medium. The simulation is based on use of Green's function of medium response to single external pulse. The process of radiation propagation is studied in the area with given boundary conditions, taking into account the processes of reflection and refraction at the boundaries of layers inside the medium under study. Results of Monte Carlo simulation were compared with experimental investigations and demonstrated good agreement.
Erythema and pigmentation are the most important visible phenomenons in the ultraviolet irradiated skin. The diffuse reflection has long been used to in vivo monitor skin chromophores (hemoglobin and melanin). In this paper, the temporal behavior of the autofluorescence spectra (excitation wavelength 337 nm) of the human skin under ultraviolet irradiation (4 MED) are presented. A simple model of the skin was used for analysis of blood content in different skin layers. In vivo autofluorescence measurements are suggested for improving the precise detection of blood and melanin content in the human skin.
Reflectance and fluorescence spectroscopy are successfully used for skin disease diagnostics. Human skin optical parameters are defined by its turbid, scattering properties with nonuniform absorption and fluorescence chromophores distribution, its multilayered structure, and variability under different physiological and pathological conditions. Theoretical modeling of light propagation in skin could improve the understanding of these conditions and may be useful in the interpretation of in vivo reflectance and autofluorescence spectra. In the present work the temporal behavior of in vivo reflectance and autofluorescence (excitation wavelength 337 nm) spectra of human skin under ultraviolet irradiation and external mechanical pressure were investigated. Experimental results and Monte Carlo modeling of light distribution in skin were compared and demonstrated good agreements. Combination of diffuse reflectance and autofluorescence measurements is a very promising technique for precise erythema and pigmentation of the human skin evaluation.
The advantages of optical spectroscopy in skin are discussed. The basis for fluorescence spectroscopy (FS) is briefly presented. The potential for in vitro and in vivo FS of biotissues is significant, but not yet well developed. Resolution of autofluorescence spectra into discrete excitation-emission bands is presented, related to various skin fluorophores.
Determination of the optical parameters of tissues is a necessary element of laser medical diagnostics and therapy planning. In this work a mathematical model of the photon migration in tissues is considered in the assumption of the harmonic modulation of the incident laser light. The scattering coefficient and the photon's life time in virtually absorbed state can be calculated from the modulation coefficient and phase shift between incident and scattered light. Frequency-domain measurements were performed using two laser diodes (wavelengths 805 and 850 nm) as light-modulated sources and fiber-optic light guides for delivering the light to tissues surface and collecting the back scattering output. It is shown that measured difference in phase shift of scattered light intensity is proportional to difference in mean pathlength of photons at two wavelengths.
The advantages of optical spectroscopy in skin are discussed. The basis for fluorescence spectroscopy is briefly presented. The potential for in vitro and in vivo fluorescence spectroscopy of biotissues is significant, but not yet well developed. With the help of fluorescence spectroscopy and layer-by-layer skin surface strippings technique the important knowledge for autofluorescence spectra from different skin layers have been obtained. Resolution of autofluorescence spectra into discrete excitation-emission bands is presented, related to various skin fluorophores.
In this paper, demonstrating necessity to take into consideration the erythema as a factor, leading to distortion of skin autofluorescence spectra during in vivo investigations of skin by the method of fluorescence spectroscopy, are presented.
Experiments on the determination of the possibilities of laser fluorescent spectroscopy for detecting the spatial distribution and time of presence of methoxypsoralens in human epidermis have been carried out.
Experiments on the determination of the possibilities of laser fluorescent spectroscopy for detecting the distribution and time of presence of methoxypsoralens (chemical substances of furocoumarin class) in human epidermis have been carried out.
In the present paper the method and apparatus for percutaneous laser irradiation of blood (PLIB) in vessels (veins) and for irradiation of not large skin tumors are described. The problems of laser light dosimetry by irradiation of tissues are discussed. Results of clinical investigations of biostimulating effects under PLIB by red laser light (633 nm) in Cubiti and Saphena Magna veins are presented.
Intravascular and percutaneous irradiation of blood by low power light of He-Ne laser (wavelength 632.8 nm) is used for therapy of a wide range of diseases. Proof and optimization of photobiostimulation of human organism depends on the results of investigations in the following areas: (1) clarification of the physical and chemical mechanisms of biostimulation; (2) development of mathematical and physical methods of laser light dosimetry within tissues; and (3) accumulation of impartial clinical information. In the paper, a short survey of the hypotheses of red laser light biostimulating effect on blood is made, the problems of dosimetry during percutaneous laser treatment of blood are discussed and some results of clinical investigations are presented.
When assessing the quality of plant-growing products, besides determining their main constituents, such as protein, oil, carbohydrates, moisture, it is often necessary to analyze the content of biologically active compounds, which
are present in considerably lower amounts. Among them, carotenoids are the natural pigments, whose biological
value is connected with a provitamine activity as well as with an effective participation in the processes of photosynthesis
and prevention of singlet oxygen photogeneration. The presence of carotenoids determines the semolina
color, which is one of the important criteria for raw material quality in the production of paste.
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