ABSTRACT
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. The issues reported comprise a brief review of optical properties of biological tissues and efficacy of optical clearing (OC) method in application to monitoring of diabetic complications and visualization of blood vessels and microcirculation using a number of optical imaging technologies, including spectroscopic, optical coherence tomography, and polarization- and speckle-based ones. Molecular modeling of immersion OC of skin and specific technique of OC of adipose tissue by its heating and photodynamic treatment are also discussed.
Subject(s)
Optical Imaging/methods , Skin , Animals , Blood Vessels/chemistry , Blood Vessels/diagnostic imaging , Cerebral Cortex/blood supply , Cerebral Cortex/diagnostic imaging , Collagen/chemistry , Glycerol/chemistry , Humans , Male , Mice , Rabbits , Rats , Refractometry , Skin/blood supply , Skin/diagnostic imaging , Tail/blood supply , Tail/diagnostic imagingABSTRACT
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. We experimentally evaluate to what extent the optical chirality affects the measurement results in typical situations and show under what conditions it can be easily taken into account and does not hinder, but rather helps, in characterization of collagen fiber alignment.
Subject(s)
Collagen/analysis , Collagen/chemistry , Image Processing, Computer-Assisted/methods , Microscopy, Polarization/methods , Animals , Rats , Sclera/chemistry , Skin/chemistry , SwineABSTRACT
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.
Subject(s)
Models, Theoretical , Nanoparticles/chemistry , Titanium/chemistry , Absorption , Algorithms , Light , Scattering, Radiation , Spectrophotometry, Ultraviolet/methodsABSTRACT
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 2.6 at 473 nm. This peculiarity is caused by the very large scattering efficiency of scatterers in the vicinity of the first Mie resonance.
