Yury P. Sinichkin

In vitro and in vivo study of dye diffusion into the human skin and hair follicles

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.

A study of polarization decay as applied to improved imaging in scattering media

Polarization decay of linearly polarized light propagating in a multiply scattering isotropic medium with embedded model inhomogeneity (absorbing half-plane) is studied experimentally and by means of Monte Carlo simulation. Possibilities of polarization visualization and the location of inhomogeneities masked by scattering media are discussed on the basis of results obtained after comparison with direct measurements of the spatial distribution of the intensity of the scattered light.

Polarization-sensitive speckle spectroscopy of scattering media beyond the diffusion limit

A scattering-media-characterization method that uses partially coherent radiation and polarization discrimination of multiply scattered light is described. The method is based on an analysis of the dependence of speckle contrast on the coherence length of the probe light. Polarization discrimination of detected speckles makes it possible to select scattered-light components that propagate in the probed medium at different distances. A theoretical analysis of the polarization-dependent speckle contrast as influenced by the probe-light coherence and parameters of the probed medium is presented. Experimental results obtained with various nondiffuse scattering samples are presented.

Attenuated total reflection Fourier transform infrared and polarization spectroscopy of in vivo human skin ablated, layer by layer, by erbium:YAG laser

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).

Digital imaging of human skin

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.

Estimation of melanin content in iris of human eye: prognosis for 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.

Immersion optical clearing of the human skin: in vivo studies

Summary form only given. Controlling of skin optical properties related to the immersion of refractive indices of scatterers (keratinocytes components in epidermis, collagen and elastin fibers in dermis) and ground matter is a key technique for structural and functional imaging. For in vivo studies of clearing of the human skin two optical techniques were used: reflectance spectroscopy and OCT. The intra dermis injection of 40% glucose was applied as the immersion procedure. Based on our proposed skin clearing model, we suggest that the main contribution to clearing in the first stage (first hour) is due to the refractive index matching between collagen fibrils of the dermis (n = 1.46) and the interstitial space (initially n = 1.36) to which glucose (n = 1.39) diffuses.

Melanin spatial distribution in the iris of the human eye

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.

Effect of the skin optical anisotropy on the polarization state of transmitted light with initial linear polarization

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.

Polarization-sensitive low-coherence speckle spectroscopy of scattering media

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.