We study fluorescence lifetime of indocyanine green (ICG) using femtosecond laser and sensitive detection based on time-correlated single-photon counting. A time-resolved multichannel spectral system is constructed and applied for determination of the fluorescence lifetime of the ICG in different solvents. Emission properties of ICG in water, milk, and 1% intralipid solution are investigated. Fluorescence of the fluorophore of different concentrations (in a range of 1.7-160 μM) dissolved in different solutions is excited by femtosecond pulses generated with the use of Ti:Sa laser tuned within the range of 740-790 nm. It is observed that fluorescence lifetime of ICG in water is 0.166 ± 0.02 ns and does not depend on excitation and emission wavelengths. We also show that for the diffusely scattering solvents (milk and intralipid), the lifetime may depend on the dye concentration (especially for large concentrations of ICG). This effect should be taken into account when analyzing changes in the mean time of arrival of fluorescence photons excited in ICG dissolved in such optically turbid media.
The paper presents a practical study of several methods of image analysis applied to polarimetric images of regular and
malignant human tissues. The images of physiological and pathologically changed tissues from body and cervix of
uterus, intestine, kidneys and breast were recorded in transmitted light of different polarization state. The set up of the
conventional optical microscope with CCD camera and rotating polarizer's were used for analysis of the polarization
state of the light transmitted through the tissue slice for each pixel of the camera image. The set of images corresponding
to the different coefficients of the Stockes vectors, a 3×3 subset of the Mueller matrix as well as the maps of the
magnitude and in-plane direction of the birefringent components in the sample were calculated. Then, the statistical
analysis and the Fourier transform as well as the autocorrelation methods were used to analyze spatial distribution of
birefringent elements in the tissue samples. For better recognition of tissue state we proposed a novel method that takes
advantage of multiscale image data decomposition The results were used for selection of the optical characteristics with
significantly different values for regular and malignant tissues.
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