Biomedical subjects

Alexander P Sviridov

Publications and source records attributed to Alexander P Sviridov.

6 recordsLinked to original sources

PubMed2006

Monitoring of tissue thermal modification with a bundle-based full-field speckle analyzer.

Speckle-contrast monitoring of laser-mediated tissue modification is examined for the specific case of delivery of speckle-modulated light from the tissue to detector (CCD camera) with a fiber-optic element (bundle). The influence of the transfer properties of a bundle-based optical system on the decorrelation rate of detected dynamic speckles is analyzed. Compared with the widely used method on the base of speckle-contrast analysis in the image plane, the considered technique is characterized by a more pronounced correlation between variations of the contrast of time-averaged speckle patterns and changes in the temperature of the modified tissue. The possibility of characterization of the modification kinetics (in particular, by the evaluation of the characteristic activation energy) using the developed speckle technique is demonstrated.

Animals↗

PubMed2003

Temperature alterations of infrared light absorption by cartilage and cornea under free-electron laser radiation.

Like pure water, the water incorporated into cartilage and cornea tissue shows a pronounced dependence of the absorption coefficient on temperature. Alteration of the temperature by radiation with an IR free-electron laser was studied by use of a pulsed photothermal radiometric technique. A computation algorithm was modified to take into account the real IR absorption spectra of the tissue and the spectral sensitivity of the IR detector used. The absorption coefficients for several wavelengths within the 2.9- and 6.1-microm water absorption bands have been determined for various laser pulse energies. It is shown that the absorption coefficient for cartilage decreases at temperatures higher than 50 degrees C owing to thermal alterations of water-water and water-biopolymer interactions.

Animals↗

PubMed2002

Speckle-contrast monitoring of tissue thermal modification.

Measurements of the contrast value of time-averaged speckle-modulated images of cartilage tissue are used to study tissue thermal modification in the case of laser-light treatment. This modification is related to thermally induced internal stress relaxation in the matrix of the treated tissue. The specific feature of the evolution of time-averaged speckle contrast with a change in the current temperature of modified collagen tissue is the typical looplike form of the contrast-temperature dependencies associated with irreversible changes in tissue structure and correlated with changes in the tissue diffuse transmittance and the tissue internal stress mentioned by other researchers.

Animals↗

PubMedDate not supplied

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).

Algorithms↗

PubMedDate not supplied

Enhancement of hidden structures of early skin fibrosis using polarization degree patterns and Pearson correlation analysis.

The skin of athymic nude mice is irradiated with a single dose of x-ray irradiation that initiated fibrosis. Digital photographs of the irradiated mice are taken by illuminating the mouse skin with linearly polarized probe light of 650 nm. The specific pattern of the surface distribution of the degree of polarization enables the detection of initial skin fibrosis structures that were not visually apparent. Data processing of the raw spatial distributions of the degree of polarization based on Fourier filtering of the high-frequency noise improves subjective perception of the revealed structure in the images. In addition, Pearson correlation analysis provides information about skin structural size and directionality.

Algorithms↗

PubMedDate not supplied

Visualization of biological texture using correlation coefficient images.

Subsurface structural features of biological tissue are visualized using polarized light images. The technique of Pearson correlation coefficient analysis is used to reduce blurring of these features by unpolarized backscattered light and to visualize the regions of high statistical similarities within the noisy tissue images. It is shown that under certain conditions, such correlation coefficient maps are determined by the textural character of tissues and not by the chosen region of interest, providing information on tissue structure. As an example, the subsurface texture of a demineralized tooth sample is enhanced from a noisy polarized light image.

Humans↗