Propagation of low-frequency waves in biological tissues and vessels

Elastic surface waves in biotissue are considered taking into account its structure, and dispersion dependences are presented. Effects of contact of vibroacoustic action on the soft tissue of a human’s arm are studied, and the biotissue activity manifests itself as a vibroreaction with different characteristic times. A thermodynamic approach to the construction of rheological relations of active mechanochemical media is described. Dispersion characteristics of acoustic processes in passive and active blood vessels are given.     

Continuous optical coherence tomography monitoring of nanoparticles accumulation in biological tissues

In this study, dynamics of nanoparticles penetrating and accumulating in biotissue (healthy skin) was investigated in vivo by the noninvasive method of optical coherence tomography (OCT). Gold nanoshells and titanium dioxide nanoparticles were studied. The processes of the nanoparticles penetration and accumulation in biotissue are accompanied by the changes in optical properties of skin which affect the OCT images. The continuous OCT monitoring of the process of the nanoparticles penetration into skin showed that these changes appeared in 30 min after application of nanoparticles on the surface; the time of accumulation of maximal nanoparticles concentration in skin was observed in period of 1.5–3 h after application. Numerical processing of the OCT signal exhibited the increase in contrast between upper and lower parts of dermis and contrast decay of the hair follicle border during 60–150 min. The transmission electron microscopy technique confirmed accumulation of the both types of nanoparticles in biotissue. The novelty of this study is presentation of OCT ability to in vivo monitor dynamics of nanoparticles penetration and their re-distribution within living tissues.     

Light scattering by dielectric bodies of irregular shape in a layered medium in problems of biomedical optics: I. Theory and computational model

A mathematical model is proposed for predicting optical characteristics (refractive index and absorption coefficient) of a biotissue being simulated, which is probed in vivo by a laser beam. Blood corpuscles in this case are simulated by particles of irregular shape and various sizes, which are oriented arbitrarily in free space.     

Control of optical properties of biotissues: I. spectral properties of the eye sclera

A method for computer modeling of transmission and diffuse reflection of a strongly scattering biotissue is described. Results of calculations of spectral characteristics for a model of the human eye sclera are presented and compared with experiments. The possibility to control optical properties of biotissues is theoretically substantiated and experimentally confirmed. Variations in color indices of biotissues are calculated using theoretical and experimental spectral characteristics obtained for the eye sclera.     

Light scattering by dielectric bodies of irregular shape in a layered medium in problems of biomedical optics: II. Numerical analysis

Using the mathematical model constructed earlier, optical characteristics (refractive index and absorption coefficient) of the biotissue being simulated, probed in vivo by a laser beam, are analyzed. The action spectra of the laser radiation power absorbed by oxihemoglobin and deoxihemoglobin of blood, which are associated with selectivity of absorption of radiation by these hemoglobin derivatives, are calculated.     

Simulation of the electrophysical characteristics of a biological tissue with allowance for large-scale inhomogeneities

An electrodynamic model of reflection of a plane wave from a layer simulating a biological structure with a slowly varying thickness is constructed with allowance for roughness in the case when the characteristic size of inhomogeneities on the surface is much larger than the wavelength. The model makes it possible to vary the size of inhomogeneities on the rough surface, the electrophysical parameters of the biological sample under investigation, and the geometrical parameters and to establish the dependences between these parameters and the biological properties of the biotissue being simulated.     

Improving image quality in reflection confocal microscopy involving gold nanoparticles and osmotically active immersion liquids

We consider the possibility of using gold nanoparticles to improve the image contrast of biotissue structures in reflection confocal laser microscopy. We present the results of experimental studies using gold nanospheres with a diameter of 60 nm compared to osmotically active immersion contrast agents based on glycerol.     

Detection of Arterial Occlusions Using Viscoelastic Wave Propagation

We consider the problem of detecting cardiac artery occlusions using stenosis driven viscoelastic (VE) waves propagated through biotissue to body surface sensors. We investigate possible statistical model formulations (ordinary least squares (OLS), generalized least squares (GLS)) and post analysis techniques (residual plots) to ascertain uncertainty in estimates as well as validity of the statistical models as part of a methodology for stenosis detection using viscoelastic waves.     

Mathematical simulation of electrophysical characteristics of multiply scattering media with a fibrillar structure. II. Numerical calculations

The optical characteristics (refractive index and absorption coefficient) of the biotissue being simulated (epidermis, upper layer of derma, lower layer of derma, and blood corpuscles) are obtained using the mathematical model constructed taking into account the fibrillar structure. The quantitative estimates based on this model can be used for predicting the variations in the optical properties of biological tissue samples, which are associated with various biophysical and biochemical processes occurring in it.     

Compression as a method for increasing the informativity of optical coherence tomography of biotissues

The efficiency of the mechanical compression of biotissues for improving the differentiation between pathological changes in the structure of a biotissue observed by the method of optical coherence tomography (OCT) is investigated. The effect of the compression in the OCT-images of samples of the human rectum affected by inflammation and carcinoma is studied ex vivo. It is shown that the use of compression makes it possible to differentiate between these pathological changes. To interpret experimental data, images of an inflamed part of rectum are modeled by the Monte Carlo method for different degrees of compression. The results of modeling agree qualitatively with the experimental data.     

Measurement of optical penetration depth and refractive index of human tissue

Experimental techniques for measurement of optical penetration depth and refractive index of humantissue are presented, respectively. Optical penetration depth can be obtained from the measurement ofthe relative fluence-depth distribution inside the target tissue. The depth of normal and carcinomatoushuman lung tissues irradiated with the wavelengths of 406.7, 632.8 and 674.4 nm in vitro are respectivelydetermined.In addition,a novel simple method based on total internal reflection for measuring therefractive index of biotissue in vivo is developed,and the refractive indices of skin from people of differentage, sex and skin color are measured.Their refractive indices are almost same and the average is 1.533.     

Control of tissue mechanics upon the repetitive-pulse laser heating of cartilage

The viscoelastic properties of laser-irradiated cartilages are studied with optoacoustic methods upon the thermal excitation of mechanical oscillations by repetitive-pulse laser radiation. The effect of laser power, pulse duration, repetition rate, and irradiation time on the shape of the optoacoustic signal is analyzed. It is demonstrated that the optoacoustic response of the cartilage to the repetitive-pulse radiation of a fiber laser depends on the softening of the tissue upon the variation in its shape. Under repetitive-pulse laser irradiation, the optoacoustic response of the cartilage depends on the mechanical characteristics of the biotissue (elastic modulus, hydraulic permeability, and thickness). A simple model that makes it possible to estimate the contribution of the viscoelastic properties to the formation of the optoacoustic response at various laser repetition rates is proposed.     

Influence of Low-Intensity Laser Radiation on the Rheological Characteristics of Human Blood

The influence of low-intensity laser radiation (LLR) on the rheological characteristics of human blood has been investigated. The results of the investigation of the blood velocity in the human skin capillaries, the erythrocyte aggregation time, and the spectral width of scattering intensity fluctuations depending on the irradiation time are presented. It has been shown that laser irradiation leads to a decrease in the degree of aggregation of erythrocytes and, accordingly, to an increase in the velocity of blood microcirculation, which can be used for laser therapy and diagnostics and treatment of cardiovascular diseases (CVD). To explain the results obtained, a method of the LLR–biotissue interaction is proposed.     

光动力治疗中热效应的理论分析与计算

基于Pennes传热方程，从理论上分析了光动力治疗中激光作用所引起的组织温升的变化.结果表明，激光照射在生物组织内形成热源，该热源在一维生物组织空间引起组织的温升一般随时间呈指数形式增大，随激光照射处的距离呈指数减少.激光照射生物组织产生热效应，存在一个最小阈值光剂量，仅当照射的激光剂量大于阈值光剂量时，才能产生热效应.阈值光剂量大小由生物组织的光学参量和热物性参量决定，并随激光照射处的距离呈指数增加     

Laser swelling of soft biological tissue by IR pulses

The temporal dynamics of biological tissue swelling under the effect of mid-IR laser radiation is considered theoretically following the experimental investigation published earlier. The probable mechanism of laser swelling is suggested. This mechanism consists of deformation of tissue protein base by vapor pressure, which appears due to evaporation of tissue water. The formation and relaxation of a hump on the surface was determined by both mechanical properties (elastic, plastic) and porosity of material providing water vapor transfer within tissue. It is found that these mechanisms can lead to the formation of both transient and stationary hump structures on the surface. To describe the hump relaxation, we consider a new, evaporation-condensation, mechanism of heat transfer within the region of biotissue with microchannels. This mechanism allows us to explain the value of relaxation time of the hump measured in experiment. PACS 42.62.-b; 44.30.+v; 81.40.-z     

时域光声谱技术及其在生物组织检测中的应用

当强度调制的光束照射于吸收物质,周期性热流使周围的介质热胀冷缩而激发声波,这种将光能转化为声能的现象称为光声效应。基于光声效应的时域光声谱技术将光学和声学有机地结合,为生物组织的无损检测技术提供了新的检测手段。该技术能够实现类似光学技术的高对比度和近似于声学技术的高精度和穿透深度,在生物医学检测中具有广阔的应用前景。文章介绍时域光声谱技术的原理及其在生物组织成分检测和层析成像检测中的应用。     

Noninvasive optical method for determining the scattering coefficients and the specific volume of blood in biological tissue <Emphasis Type="Italic">in vivo</Emphasis>

We propose a method for determining the scattering coefficients of biological tissue and changes in the relative volume of blood. The method is based on the difference of the parameters of optical radiation that has passed through a biological tissue and the radiation scattered by it in the opposite direction. The obtained correlations between the ratio of the scattered light modulation coefficients at two wavelengths and the biotissue parameters permits determination of the tissue characteristics directly in the living organism. The scattering coefficients at different wavelengths and the values of the relative volume of blood for different anatomical zones and its changes during physiological loads have been calculated.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 119–123, January–February, 2005.     

肿瘤射频热疗SAR场与瞬时温度分布模拟

本文针对非侵入性射频热疗的SAR场及瞬态温度分布进行建模和数值模拟计算。采用了能正确反映电磁波在生物组织中衰减的电磁场模型。在温度场模拟中考虑了血液灌流项随组织温度变化和肿瘤区低血液灌流的特点,这些措施使模拟计算结果更加符合临床实际。还对射频热疗电磁能量分布和温度分布的特点及其影响因素等作了细致的分析和讨论。     

Dynamic laser prototyping for biomimetic nanofabrication

Micronanofabrication technologies developed so far pursue faithful conversion from digital models to matter structures. This is vital for microdevices in optics, mechanics, and electronics, where device shape and size matter. However, biotissues grow under rich environmental factor interactions, as demands novel manufacturing approaches for biomimetic and biological fabrication. Here, a concept of dynamic laser prototyping is reported, which is based on a new finding of a multilayered three‐dimensional (3D) wrinkling phenomenon. The 3D wrinkling started with formation of a photocrosslinked hydrogel sheet by femtosecond laser direct writing. It was followed by spontaneous self‐bending of the sheet, caused by a purposely designed sheet–substrate stress mismatch. The flower blooming process has been successfully mimicked, indicating broader usages of the technology in biotissue‐growth‐related manufacturing.