Measurement of tissue optical properties in the context of tissue optical clearing.

Nowadays, dynamically developing optical (photonic) technologies play an ever-increasing role in medicine. Their adequate and effective implementation in diagnostics, surgery, and therapy needs reliable data on optical properties of human tissues, including skin. This paper presents an overview of recent results on the measurements and control of tissue optical properties.

Quantitative mapping of collagen fiber alignment in thick tissue samples using transmission polarized-light microscopy.

Immersion optical clearing makes it possible to use transmission polarized-light microscopy for characterization of thick (200 to 2000  μm) layers of biological tissues. We discuss polarization properties of thick samples in the context of the problem of characterization of collagen fiber alignment in connective tissues such as sclera and dermis. Optical chirality caused by azimuthal variations of the macroscopic (effective) optic axis of the medium across the sample thickness should be considered in polarization mapping of thick samples of these tissues.

Resonant scattering and absorption in the titanate-based nanoplatelet dispersions in near ultraviolet region.

Extinction enhancement and nonlinear near-resonant absorption of potassium polytitanate nanoplatelets were experimentally studied in the near-UV region. Phenomenological models such as the one-oscillator Lorentz model for dielectric function and the two-level model with the depleted ground state were used to interpret the experimental data. The introduced model parameters demonstrate the adequately high sensitivity to variations in nanoplatelet morphology and chemical environment.

[Potentialities of autofluorescent spectroscopy in diagnosis of laryngeal and pharyngeal tumors].

Laryngeal and pharyngeal mucosa of 50 patients with malignant (n=56%) and benign (n=44%) laryngeal and pharyngeal tumors was examined with autofluorescent spectroscopy using nitrogen laser LGI-505 (337,1 nm). It was found that autofluorescent spectrum of malignant tumors is significantly less intensive than relevant spectrum of healthy mucosa and benign tumors.

Random media characterization using the analysis of diffusing light data on the basis of an effective medium model.

The transport properties of dense random media such as rutile powder layers and polyball suspensions are analyzed in visible and near infrared on the basis of experimental data on coherent backscattering, diffuse transmittance, and low-coherence interferometry. The developed technique of retrieval of the transport parameters of examined scattering media allows the evaluation of the transport mean free path l* and the effective refractive index n(ef) of the medium without a priori knowledge of the optical properties of the scattering particles. It is found that with decreasing wavelength lambda(0) the value of localization parameter 2pin(ef)l*/lambda(0) of the studied rutile samples abruptly drops and approaches approximately 2.

Optical clearing of skin using flash lamp-induced enhancement of epidermal permeability.

Background And Objectives: Strong light scattering in skin prevents precise targeting of optical energy in therapeutic and diagnostic applications. Optical immersion based on matching refractive index of scattering centers with that of surrounding matter through introduction of an exogenous index-matching agent can alleviate the problem. However, slow diffusion of the index-matching agent through skin barrier makes practical implementation of this approach difficult.