Sergey S. Ulyanov

Investigation of statistical properties of lymph-flow dynamics using speckle microscopy

At different pathological stages, the changes both of blood and lymph microcirculation parameters are observed. These parameters are of great importance in diagnostics. The type of these changes may indicate both the kind and the degree of disease. Investigation of the behavior of dynamic characteristics of these flows at different stages is of special interest. In this paper the peculiarities both of blood and lymph motion have been considered. The further development of speckle-interferometrical method has been carried out for the investigation of the dynamic characteristics of blood and lymph flows in microvessels. Analysis of two dynamic parameters which had been introduced in previous papers concerning this problem, is made in this paper. The influence of lymphotropic agent both on lymph flow and its dynamic characteristics is also discussed.

Pulse-wave monitoring by means of focused laser beams scattered by skin surface and membranes

The methods of the analysis of angular and shear cardiovibrations have been developed. The experimental results of vibration investigations using these methods are presented. The advantages and deficiencies of the methods are discussed.

Speckled speckle statistics with a small number of scatterers: implication for blood flow measurement.

Formulas relating to diffraction of the focused Gaussian beam from a narrow blood microvessel have been derived. A native vessel has been considered as a set of moving random screens. The correlation function of intensity fluctuations of statistically inhomogeneous speckled speckles has been studied with applications to flow measurement. Dependencies of statistical characteristics of biospeckles with a small number of scatterers on the number of scattering screens have been analyzed. It has been shown that the value of Doppler shift in the scattered light essentially depends on the spatial velocity distribution in the blood flow.

Blood-flow measurements with a small number of scattering events

Results of simulations of the diffraction of a laser beam by a small blood vessel imbedded in scattering tissue are presented. The form of the spectra of biospeckle intensity fluctuations is analyzed. The Doppler shift of intensity fluctuations of scattered light is investigated as a function of the laser beam radius, the radius of the blood vessel, the depth of the vessel in the tissue, and the scattering characteristics of flowing blood. A formula that serves as the basis for a method of absolute measurements of blood-flow velocity is derived.

Fundamentals and applications of dynamic speckles induced by focused laser beam scattering

Speckle intensity first-order statistics for a large-scale scattering structure is investigated. Results of computer simulation and experimental studies of coherent light diffraction by large-scale scattering objects are presented. The correlation characteristics of dynamic speckles induced by focused Gaussian beam diffraction is theoretically and experimentally analyzed.

Speckle interferometry for biotissue vibration measurement

We consider the mechanism of the speckle interlerometer output signal formation for biovibration measurements. Statistical characteristic analysis of the output signal amplitude is carried out. The factors creating amplitude-phase modulation of the output signal are investigated. The possibility of a differential homodyne speckle interferometer application in Tibetan pulse diagnostics is demonstrated.

New type of manifestation of the Doppler effect: an application to blood and lymph flow measurements

Based on theoretical and experimental analyses, it is shown that the spectrum of intensity fluctuations contains a high-frequency peak in the absence of a subsidiary reference wave at nonsmall angles of speckle observation. This phenomenon, interpreted as a new type of manifestation of the Doppler effect, is usual only for the case of strongly focused coherent beam scattering. The possibilities for using the observed effect in the measurements of blood and lymph flows in narrow native capillaries are discussed. The traditional Doppler method using strongly focused Gaussian beam scattering is also considered. It is shown that the frequency position of the Doppler peak in the spectrum of intensity fluctuations is defined not only by the angle of speckle observation but also by the relation between the waist beam diameter and the average size of flow inhomogeneities. This result was experimentally verified. It is concluded that the Doppler method of blood flow measurement using strongly focused Gaussian beam diffraction should be revised.

Correlation properties of multiple scattered light: implication to coherent diagnostics of burned skin

Modeling of skin burns has been performed in this study. Autocorrelation functions of intensity fluctuations of scattered light were measured for two-layered turbid media. The first layer served as a model for motionless scatterers (optically inhomogeneous gel film) whereas the second one simulated dynamic light scattering (Brownian motion of intralipid particles in aqueous suspension). This medium was used as a model of skin burns. A theory related quasi-elastic light scattering measurements to cutaneous blood flow was used. The dependencies of statistical properties of Doppler signal on the properties of burned skin as well as on the velocity of cutaneous blood flow have been investigated. Theoretical predictions have been verified by measurements both of dynamic and stationary light scattering in model media.

The application of speckle interferometry for the monitoring of blood and lymph flow in microvessels

This paper presents a brief overview of several techniques developed for the analysis of blood microcirculation in vivo. Both theoretical and experimental investigations have been performed using focused Gaussian beams, which are diffracted by blood capillaries with diameters slightly larger than the erythrocyte. Speckle interferometry, utilizing the diffraction of a focused Gaussian beam, was used for the analysis of lymph circulation in native microvessels. The spectra of scattered intensity fluctuations produced by diffraction in such capillaries are analysed, and variations in the envelope of the spectra induced by the influence of drugs on the lymph vessels have also been studied.

LASCA with a small number of scatterers: Application for monitoring of microflow

LASCA, combined with cross-correlation technique, has been applied for high-resolution measurements of the velocity of microflow and its structure in small blood capillaries in vivo. Such measurements have been carried out for the first time behind the resolution limit of the optical system.