Morphological changes in blood vessels produced by hyperosmotic agents and measured by optical coherence tomography

Optical tissue clearing by hyperosmotic chemical agents significantly increases light depth penetration in skin and may improve light-based therapeutics such as laser treatment of cutaneous vascular lesions. A feasibility study was conducted to evaluate the potential role of optical clearing by glycerol in laser treatment of cutaneous vessels. Optical imaging was performed to investigate the morphological effects of glycerol on blood vessels of skin. Blood vessels were imaged using Doppler optical coherence tomography in in vivo hamster skin treated with glycerol. Images were obtained from the subdermal side to assess morphological changes in the blood vessels caused by glycerol and from the epidermal side to assess enhanced Doppler imaging of blood vessels. Application of glycerol to the subdermis resulted in venule stasis and for prolonged treatment times, arteriole stasis. In cases where flow remained in arterioles, an improved Doppler signal was detected from blood vessels when imaging transepidermally compared with the native condition. Intensity images indicated changes in blood optical properties and improved contrast of skin cross sections after glycerol application. The observed optical and morphological effects were reversed upon hydration of the skin with phosphate-buffered saline. The combination of increased depth of light penetration and the temporary slowing or cessation of flow in blood vessels could mean improved laser treatment of vessels.     

Quantitative analysis in medicine using photoacoustic tomography

Photoacoustic imaging, or photoacoustic tomography, is a 2D or 3D optical imaging method based on localized optical absorption of pulsed laser radiation. By a spatially resolved detection of the following thermoelastic expansion, the local distribution of the absorption can be determined. The technique has been proven to have significant potential for the imaging of human and animal organs and single blood vessels, combining high contrast with good spatial resolution. The contrast is based on the specific optical absorption of certain components in the visible and near-infrared spectral range, for most applications of blood. Generally, the images represent the local distribution of blood in a qualitative or semiquantitative way. Although photoacoustic imaging is capable of revealing absolute and spatially resolved concentrations of endogenous (such as oxyhemoglobin and deoxyhemoglobin) or artificial (such as tumor markers) chromophores, only a very limited number of publications have dealt with this demanding task. In this report, the problems involved and possible solutions are reviewed and summarized.     

Optical sectioning for microfluidics: secondary flow and mixing in a meandering microchannel

Secondary flow plays a critical function in a microchannel, such as a micromixer, because it can enhance heat and mass transfer. However, there is no experimental method to visualize the secondary flow and the associated mixing pattern in a microchannel because of difficulties in high-resolution, non-invasive, cross-sectional imaging. Here, we simultaneously imaged and quantified the secondary flow and pattern of two-liquid mixing inside a meandering square microchannel with spectral-domain Doppler optical coherence tomography. We observed an increase in the efficiency of two-liquid mixing when air was injected to produce a bubble-train flow and identified the three-dimensional enhancement mechanism behind the complex mixing phenomena. An alternating pair of counter-rotating and toroidal vortices cooperated to enhance two-liquid mixing.     

LASER DOPPLER VELOCIMETRY TO QUANTIFY UV-B INDUCED INCREASE IN HUMAN SKIN BLOOD FLOW

Abstract— A laser Doppler velocimeter was used to quantify changes in cutaneous blood flow, in human subjects, after exposure to UV-B radiation. Studies with three subjects showed a peak increase in flow at 6 h post-irradiation. Dose-response studies, on 8 subjects, at 24 h post-irradiation showed that blood flow increased linearly with log UV-B dose over a range of about 0.5 to 5 MED. Comparative studies with pigmented and non-pigmented skins gave a quantitative measure of the photoprotective effect of melanin. The main advantage of the laser Doppler technique is that it allows easy quantification of a vascular response. However, there was no advantage when compared with detection of a visually determined threshold response, viz. a barely perceptible erythema.     

Remotely detected MRI velocimetry in microporous bead packs

Many NMR and MRI methods probe fluid dynamics within macro- and mesoporous materials, but with few exceptions, they report on its macroscopically averaged properties. MRI methods are generally unable to localize microscopic features of flow within macroscopic samples because the fraction of the enclosing detector volume occupied by these features is so small. We have recently overcome this problem using remotely detected MRI velocimetry, a technique in which spatial, chemical, and velocity information about elements of the flow is encoded with a conventional NMR coil and detected sensitively at the sample outflow by a volume-matched microdetector. Here, we apply this method to microporous model systems, recording MRI images that correlate local velocity, spin relaxation, and time-of-flight in microscopic resolution and three spatial dimensions. Our results illustrate that remotely detected MRI is an effective approach to elucidate flow dynamics in porous materials including bead pack microreactors and chromatography columns.     

Folding dynamics of tethered giant DNA under strong flow

Using a microfluidic device, we investigate the folding dynamics of individual linear long DNA, whose one end is tethered under a strong flow in the presence of a condensing agent. Direct observations of the folding process of DNA molecules reveal a characteristic dynamics with pronounced non-monotonic velocity of the folded part at the free end against the flow. We discuss this unique dynamics in relation to the inhomogeneous spatial fluctuation and the structure change at the multiple order levels along the stretched DNA, which is induced by the increasing tension due to the build-up of the hydrodynamic drag force.     

丙烯酸化超支化聚异酞酸酯制作微透镜

微透镜及其阵列在光学通讯、医学诊断,特别是大规模集成光路板等领域具有广泛的应用前景。目前,微透镜及其阵列的制作方法已有很多报道,如热压纹法、模型法和刻蚀法等。但制作高质量、低成本的微透镜及其阵列仍是当前研究的一个热点课题,利用丙烯酸化超支化聚合物较少链缠绕、粘度低、反应活性高等特点,在光引发剂存在下,使其快速固化成型,制得所需尺寸的微透镜。该方法的特点是在二维可移动水平玻璃基板上,树脂液滴由于其重力和表面张力而迅速形成平凸形,经紫外光曝光固化成型,形成规整的微透镜及其阵列。     

电子断层三维重构技术在材料微观结构分析中的应用

电子断层三维重构技术是在透射电镜基础上发展起来的,用以解析材料三维结构的一种技术。本文以美国FEI公司Tecnai G~2 F20透射电镜三维重构系统——Xplore 3D系统为例,探讨了样品制备与取向的选择、样品漂移问题的成因与校正、降低缺失锲存在造成的模型失真及空间分辨率的提高等问题,从以上四个方面详细介绍电子断层三维重构技术的要点及在材料微观结构方面的应用经验。     

透射电镜三维重构确定金纳米粒子的立体结构

贵金属纳米颗粒具有局域表面等离激元这一特性使其具有丰富的光学性质,而这一特性受制于纳米颗粒所形成的立体几何形状,而透射电镜和扫描电镜的二维图像不能真切地观测和确定纳米颗粒所形成的立体几何结构。透射电镜三维重构技术可作为一种确定纳米颗粒立体结构的直观有效的方法。本文利用透射电镜的三维重构技术,选择合适的参数进行二维图像的采集、图像匹配对中及重构、立体模型的构建,从而通过构建的模型对两种金纳米颗粒样品的不同几何形状所产生的边界形态进行了确认和分析。     

Theoretical and computational investigations of nonlinear wave propagations in arteries. (I)--A theoretical model of nonlinear pulse wave propagations

In this paper, a new theoretical model of nonlinear wave propagations in arteries with surrounding tissues was put forward. The equations of motion for the blood vessels and their peripheral tissues as a system have been derived. These equations were expressed in terms of the stresses of the vessel wall and fluid, and the geometry of the blood vessel. They can be used to solve numerically the problems for the propagations of nonlinear pulse waves in arteries together with the momentum and continuity equations of incompressible-viscous flow, as well as the constitutive equations of fluid and vessel wall. The numerical solutions can involve pressure, velocities and flowrate of the blood flow, as well as displacements, velocities and stresses of the vessel wall. These physical variables of propagations of pulse waves in arteries are all of significance physiologically and clinically.     

THEORETICAL AND COMPUTATIONAL INVESTIGATIONS OF NONLINEAR WAVE PROPAGATIONS IN ARTERIES (Ⅰ)——A THEORETICAL MODEL OF NONLINEAR PULSE WAVE PROPAGATIONS

In this paper, a new theoretical model of nonlinear wave propagations in arteries with surrounding tissues was put forward. The equations of motion for the blood vessels and their peripheral tissues as a system have been derived. These equations were expressed in terms of the stresses of the vessel wall and fluid, and the geometry of the blood vessel. They can be used to solve numerically the problems for the propagations of nonlinear pulse waves in arteries together with the momentum and continuity equations of incompressible-viscous flow, as well as the constitutive equations of fluid and vessel wall. The numerical solutions can involve pressure, velocities and flowrate of the blood flow, as well as displacements, velocities and stresses of the vessel wall. These physical variables of propagations of pulse waves in arteries are all of significance physiologically and clinically.     

Listen to the chemical and histological information in biological tissue

Photoacoustic imaging (PAI), as an emerging biomedicine diagnostic technique that has been developed quickly in the past decade, inherits the high spatial resolution of ultrasonography in imaging deep tissue and the high sensitivity of optical imaging in evaluating tissue chemical and physiological information. In this paper, after introducing the basic principles of PAI including both photoacoustic tomography and photoacoustic microscopy, we will review some recent progress of PAI in biomedicine and demonstrate the capability of PAI in detecting the chemical compositions and in evaluating the histological microstructures in biological tissue.     

Polymer melt flow measurements by laser doppler velocimetry

Laser Doppler velocimetry (LDV) is a new tool for fluid dynamics studies. Using LDV the velocity vector field can be measured without disturbing the flow itself. However, in polymer melt fluid dynamics difficulties arise because of temperature problems, the relatively high pressure involved, and the often extremely slow flows. In this paper a LDV system is described which was set up especially for polymer melt flow investigations.     

Blood flow and oxygen transfer rate of an outside blood flow membrane oxygenator

We evaluated effects of the number of tied hollow fibers of an outside blood flow membrane oxygenator with cross-wound hollow fibers on the blood flow pattern and oxygen transfer rate. The number of tied hollow fibers in a bundle was varied from one to six, and the blood flow pattern was observed by X-ray computed tomography. The oxygen transfer rate and blood pressure drop were measured by in vitro experiments using bovine blood. Uniform blood flow patterns were obtained for each number of tied hollow fibers. A decrease in the number of tied hollow fibers caused more effective contact of blood with the tied hollow fibers and oxygen transfer rate was enhanced, demonstrating that single hollow fiber was the most effective. Empirical equations were obtained based on these results and optimum structure parameters of the membrane oxygenator were determined by simulation analysis. Optimum membrane surface area and axial jacket length of the oxygenator were 3.0 m² and 320 mm, respectively, at a hollow fiber outside diameter of 250 μm.     

Fundamental imaging properties of transillumination laser computed tomography based on coherent detection imaging method.

The coherent detection imaging (CDI) method uses the optical heterodyne detection technique. CW and single frequency lasers having long coherence lengths are used to exploit the maximum advantages of heterodyne detection, such as high directionality, selectivity and sensitivity. The CDI method based on optical heterodyne detection enables selective filtering of the directional coherence-retaining emergent photons, which leads to image reconstruction from projections, similar to X-ray computed tomography (CT). So far we have demonstrated the advantages and capabilities of the measurement technique for transillumination optical computed tomography in biomedicine. Here, we investigate the fundamental imaging properties of CDI method, such as its high directionality and quantitativeness, with preliminary physical phantom experiments. The results show that the CDI method satisfies the requirements for CT reconstruction under the first order approximation, and enables quantitative measurements in the sense that the relationship between estimated and actual concentration retains a satisfactory linearity.     

Longitudinal 3D Blood Flow Distribution Provided by Diffuse Correlation Tomography during Bone Healing in a Murine Fracture Model

Noninvasive monitoring of vascularization can potentially diagnose impaired bone healing earlier than current radiographic methods. In this study, a noncontact diffuse correlation tomography (DCT) technique was employed to measure longitudinal blood flow changes during bone healing in a murine femoral fracture model. The three-dimensional distribution of the relative blood flow was quantified from one day pre-fracture to 48 days post-fracture. For three mice, frequent DCT measurements were performed every other day for one week after fracture, and then weekly thereafter. A decrease in blood flow was observed in the bone fracture region at one day post-fracture, followed by a monotonic increase in blood flow beyond the pre-injury baseline until five to seven days post-fracture. For the remaining 12 mice, only weekly DCT measurements were performed. Data collected on a weekly basis show the blood flow for most mice was elevated above baseline during the first two post-fracture weeks, followed by a subsequent decrease. Torsional strength of the excised femurs was measured for all 15 mice after 7 weeks of healing. A metric based on the early blood flow changes shows a statistically significant difference between the high strength group and the low strength group.     

The Origin and Dynamics of Soft X‐Ray‐Excited Optical Luminescence of ZnO

The distinct optical emission from ZnO materials, nanoneedles and microcrystallites synthesized with different sizes and morphologies by a flow deposition technique, is investigated with X‐ray excited optical luminescence (XEOL) and time‐resolved X‐ray excited optical luminescence (TR‐XEOL) from a synchrotron light source at the O K and Zn L_3,2 edges. The innovative use of XEOL, allowing site‐specific chemical information and luminescence information at the same time, is fundamental to provide direct evidence for the different behaviour and the crucial role of bulk and surface defects in the origin of ZnO optical emission, including dynamics. XEOL from highly crystalline ZnO nanoneedles is characterized by a sharp band‐gap emission (～380 nm) and a broad red luminescence (～680 nm) related to surface defects. Luminescence from ZnO microcrystallites is mostly dominated by green emission (～510 nm) associated with defects in the core. TR‐XEOL experiments show considerably faster decay dynamics in nanoneedles compared to microcrystallites for both band‐gap emission and visible luminescence. Herein we make a fundamental step forward correlating for the first time the interplay of size, crystallinity, morphology and excitation energy with luminescence from ZnO materials.     

Tumor blood-flow changes following protoporphyrin IX-based photodynamic therapy in mice and humans

The effects of aminolevulinic acid (ALA)-based photodynamic therapy (PDT) on tumor blood flow are controversial. This study examines the effects of ALA and Photofrin-based PDT on blood flow of Colon-26 tumors implanted in mice as well as the effects of ALA-based PDT on blood flow of human colorectal carcinomas and a carcinoid tumor in situ. Tumors are implanted in both flanks of mice. One tumor of each animal serves as a control. Blood flow is measured using a laser Doppler method. Tumor blood flow in mice not receiving a photosensitizer but treated with three different light fluences (50, 100 and 150 J/cm2) does not differ significantly from blood flow in the untreated tumor in the opposite flank. PDT after ALA administration using the three different light fluences does not significantly affect blood flow. In contrast, PDT after Photofrin administration causes a significant decrease in tumor blood flow with each light fluence, but this change is not as dramatic as reported in other studies. In contrast to mice, six patients who receive ALA prior to surgery all show a decrease in blood flow (mean = 51.8%, p < 0.001) after PDT using 100 J/cm2. Comparison with other published results suggests that it is likely that flow measurement by the laser Doppler method underestimates the effects of PDT on tumor blood flow due to the depth of laser penetration. Nevertheless, the present observations on blood flow suggest that the effects of ALA-based PDT on adenocarcinomas of the colon and rectum as well as an intra-abdominal carcinoid tumor in humans are more pronounced than would be predicated by some animal studies.     

Monitoring morphological and optical properties on hybrid porous polymer films

This work focuses on an optical and morphological comparative study of hybrid functional polymer porous films on glass substrates using the spin coating technique. The covering of these membranes, by a predeposited Zn²⁺ seed layer, was done applying the dip casting technique, which allows the synthesis of a large area and the control of the orientation of ZnO nanoparticles. It was possible to observe changes on the optical properties and surface morphology, which were attributed to both the spatial structure of the macromolecule and their interaction with the inorganic nanoparticles. It was also clear that hybrid porous matrices exhibit a blueshift with decreasing particle size.     

Adhesion behaviors of human trophoblast cells by contact with endothelial cells

Although it is still not clear whether migratory trophoblasts reach the spiral arteries by migration within blood vessels against blood flow or by a mechanism of directional cell division/proliferation, this process involves the attachment and adhesion of trophoblasts to endothelial cells lining the blood vessel walls. This raises the possibility that the cell–cell contact with endothelial cells may regulate trophoblast cell adhesion behaviors according to the surrounding flow condition. To test this, the adhesion forces of early gestation human trophoblast cells (TCs) cultured on glass slides coated with type I rat collagen or cultured with human umbilical vein endothelial cells (HUVECs) were measured quantitatively using a micropipette aspiration technique. Then, the resistance of TCs co-cultured with HUVECs to flow-induced shear stress was assessed with a flow chamber technique. The results showed that the adhesion force of TCs to glass slides coated with collagen was positively correlated with the concentration of collagen. By contact with endothelial cells, the adhesion force and the resistance to shear stress for the TCs were significantly enhanced. The interdiction of integrin β1 interaction remarkably reduced the adhesion forces of TCs to endothelial cells, hence their resistance to shear stress. The results therefore suggest that the contacts of TCs with endothelial cells enhance the adhesion forces of human TCs, partially by regulating with the integrin β1 according to the flow condition (i.e., the shear stress) in such a way to prevent the TCs from being carried downstream by flowing blood.