Svetlana P. Chernova

Dynamics of optical clearing of human skin in vivo

Two ways of improving the skin permeability to clearing agents has been suggested and tested: i. Removal of upper layers of epidermis by glue stripping, ii. Electrophoretic administration of clearing agent into intact skin. Alterations in light scattering by skin under continuous contact with the agent were monitored by the measurement of diffuse reflectance of tissue at 830nm.

Physical modeling of tissue fluorescence: phantom development

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).

Special training laboratory on optical biophysics

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.

Autofluorescence of human epidermis under UV irradiation in vitro

We studied autofluorescence of the layers of normal human epidermis in the course of the development of less invasive technique for assessment of tissue state. Surface epidermal stripping technique was applied to spectrofluorimetric study of epidermis. Three bands (280 plus or minus 20 nm, 360 plus or minus 20 nm, 435 plus or minus 20 nm) were used for excitation of sample fluorescence. Some well reproducible autofluorescence bands were observed over all samples. Data averaged over the group of volunteers are indicative of the decrease of intrinsic epidermis fluorophores content with depth. Alterations in fluorescence of samples of different epidermal layers under storage were studied as well as the dynamics of autofluorescence degradation in just taken strippings under continuous UV irradiation.

Optical testing of human epidermis

Technology for human epidermis optical parameters determination is described. This technology includes: (1) epidermis upper layers glue stripping; (2) in vitro measurements of total transmission, diffuse reflection, and angular light scattering of strippings; (3) absorption and scattering coefficients reconstruction using inverse calculating technique based on 4-flux approximation of radiation transport theory or inverse Monte Carlo simulation method. Epidermis stripping autofluorescence spectra were acquired under different excitation wavelengths: dependence of sample autofluorescence on some external factors was followed.

One approach to the description of multilayer tissue fluorescence

The adequacy of simple optical model of three-layer fluorescent phantom of biotissue with optically thick lowest layer has been shown. In the series of samples with varied epithelium thickness, epithelium scatterer concentration, and stromal blood content, the differences between model predictions and recorded fluorescence spectra were reasonably small.

Photobleaching of fluorescence of NADH in gelatin gel

The process of photobleaching of fluorescence of NADH in gelatin gel under UV irradiation has been studied. An attempt to evalute the NADH fluorescence contribution to 460-480 nm fluorescence of the samples from bleaching data has been made.

Contribution of glue layer into epidermis sample fluorescence dynamics

In this work, the temporal behavior of autofluorescence of epidermis samples under UV-irradiation has ben studied. The samples were prepared using surface epidermis stripping technique. Fluorescence spectra and kinetic curves of fluorescence intensity have been obtained. It has been concluded that the glue composition used allows the measurement of epidermis fluorescence dynamics with the first 60 min of experiment.

Ex-vivo and phantom fluorescence spectra of human cervical tissue

In present work, fluorescence spectra of normal cervical tissue as well as some benign lesions were obtained ex vivo with 365 +/- 20 nm and 405 +/- 30 excitation. In all case of ectopia emissions from normal area appeared more intensive than from pathological one. Intensive fluorescence with specific spectral lineshape was observed on the posttraumatic scars, the main contribution to the spectrum was attributed to collagen. On the base of phantom measurement, explanation of appearance of a weak peak at 505-515 nm in tissue fluorescence spectra was proposed.

Layered Gel-Based Phantoms Mimicking Fluorescence of Cervical Tissue

In recent decades autofluorescence spectroscopy has proved its potential to distinguish between neoplasia and tumors and normal human tissue. When combined with endoscopic techniques and instrumentation the method has become an effective tool for noninvasive diagnosis of neoplasia and early tumors in human epithelium and subepithelium which are the tissues easily accessible to endoscopic optical probing [1–7].