笔者想苏拉的阿布Mallouh和弗雷德里克·法希姆用于测试的协议，理查德·普雷沃LaVision公司的技术支持，在初始运行，她的帮助，感谢NSERC（自然科学与工程理事会，加拿大）的资金，凯瑟琳Pagiatikis和Guy Cloutier联系蒙特利尔大学的贷款Dalsa公司高速摄像机。

1。微晶片制造第一步是创建或购买你的微通道。微芯片材料有很多的选择。 选择最常见的材料是聚（二甲基硅氧烷）（PDMS）。出版物有很多PDMS加工通过软光刻16,17,18的方向。 PDMS通道一旦被制造的，也有一些表面处理，以扭转其天然疏水性。含氧等离子体处理是一种常见的选择。 周，埃利斯，Voelcker（2009）给表面处理，以及它们如何影响PDMS评论。这些结果是水，但是，血液有不同的性质。研究已经做了什么，表面处理是指血液皮茨等人 （2012A）。 基于这里给出的结果，它们的微芯片的表面和载玻片键合到均暴露于含氧等离子体45秒，然后牢固地压合在一起造成永久粘合。 2。血液制剂<ol><li>收集血液样本认可的设施。例如猪血可以使用乙二胺四乙酸（EDTA）作为抗凝剂。添加1克乙二胺四乙酸，4毫升水，然后添加全血的1升的溶液，轻轻混合10倍。 </li></ol>当拿起血液样本，让它们慢慢冷却到室温。血液样本应该是新鲜的，理想使用的天收集血液的流变学特性，以节省。 冷藏样品可在室温下一次，然而没有抗凝全血冷冻后，将无法使用。红细胞上的抗凝血剂，可以保存在冰箱中长达42天，和全血可冷藏保存35天，但污染将有可能在一个非米兼具医疗设备21。 此外，要小心用牛或猪的样品采集方法，避免污染骨髓。 <ol start="2"><li>离心血液样品3次每次10分钟在3,000 rpm。第一次离心后，除去血浆和白膜，丢弃。它通常是最容易拆卸第一等离子体，然后丢弃或保留以供将来使用，然后以除去血沉棕黄层。 </li></ol>引入的移液管慢慢地，以便不使混回血液的血沉棕黄层。去除白膜后，加入约20毫升的磷酸盐缓冲液（PBS），轻轻混匀，recentrifuge。重复最后一步。第三次离心后，取出PBS和剩余的棕黄色大衣，丢弃。 它也可以使用本机的等离子代替PBS如果你想保持血液聚集性能。确保不能混合任何白膜或白色到血浆中的血细胞。 <ol start="3"><li>清洗红血细胞（红细胞），并悬浮在PBS或等离子在随意的浓度（血细胞比容）。检查离心比容（美国）FisherSci CritSpin，。 </li></ol>在10〜20％的血细胞比容的血应该是更容易的可视化比40或50％（生理血细胞比容）。血液微循环，一般是半宏循环的血细胞比容，所以H = 20是足够的15。 <ol start="4"><li>以所需浓度的血液样本，加入荧光示踪粒子。一般的规则是有10个颗粒，在相关窗口，它可以提前计算。 </li></ol>例如，30微升的颗粒被添加到视频中所示的设置的1毫升的血溶液。或者，可以被荧光标记的红细胞本身。 <ol start="5"><li>此外，进行校准溶液与水和流感颗粒orescing。这将是牛顿的解决方案，需要对系统进行校准。 </li></ol>例如，当使用10倍的目标与通道上的规模为100μm，合适的浓度为300μl的颗粒用15毫升的蒸馏水混合。另一种选择是使用用蒸馏水稀释甘油的粘度为3CP，这是更接近血液的宏观粘度。 3。 μPIV测量<ol><li>激光安全:检查温度和湿度。穿戴合适的激光安全眼镜。关闭激光窗帘或打开门不被暴露保护，以防止有人在实验室的激光标志。 </li><li>戴维斯软件程序在视频显示。欲了解更多详细信息，请参阅特定系统的用户手册。 </li><li>在获取数据之前，需要进行校准相机规模使用千分尺。 </li><li>为了降低系统的合规性，用最短的油管d为最小的刚性注射器可能的，诸如15或50微升汉密尔顿气密注射器。血液或进气口，以减少泄漏到系统中，密封管连接到注射器和芯片。这是可以做到用胶水，PDMS或凡士林（小心不要污染的血液）。 </li></ol>为了填补股价与示踪粒子与水的微量注射器使用回流的方法，因为微量注射器的体积通常是远小于卷以填充。 通过我们的回流方法，包括填充微量注射器和信道的信道使用的二次塑料注射器经由输出。对于这一点，首先除去微量注射器柱塞，然后推入的液体，采用经典的塑料注射器附着到出口的通道，让液体流出来的微量注射器，直到所有的微泡的微型注射器，管或芯片，终于把柱塞回，拔下塑料注射器。的存在可以验证ŗ没有微泡，用显微镜。 <ol start="5"><li>平注射器泵实现横向管。程序注射器泵所需的流量。 </li></ol>要意识到可能短暂影响，像"瓶颈效应"，刚性的系统或系统的合规性，修改实际流量。一个系统的特征时间可估计为一个函数的系统的材料和尺寸。 （第2章，第77-81页，Tabeling，2005年） <ol start="6"><li>显微镜舞台上放置微芯片，并启动泵。使用水与颗粒校准系统到中间的速度分布图和校准DT（脉冲图像之间的时间）。 </li></ol>粒子良好的相关性11 5和10之间移动的帧之间的像素。校准时，小心衡量，在中间的通道。在中间聚焦平面具有最高的速度8。 如果使用一个圆形通道，小心的阴影效果。 图2所示的图像样本，使用脉冲的摄像头，而最佳的图像是第一个脉冲和底部的图像是第二脉冲。可以看出，图中的最亮的点（荧光颗粒）是在焦。 <ol start="7"><li>可选:数据在不同的高度的三维速度分布可以重建成一个单一的图像通过添加不同媒介。视频提出了一种的例程被开发的过程自动化。 </li><li>当患者的血液中的数据时，填充注射器与所需量的血液中的水的方法相同的方法。编程注射泵以所需流速，并采取所需的数据。获得的原始图像的一个例子，提出了如图2所示 。小心红细胞沉降。加注射器每次运行或每其他的运行会降低红细胞的沉降。 </li><li>获取图像后，进行相互相关的图像对取得的图像之间的速度矢量场。重要的是要具有良好的图像，以具有良好的相关性。关联之前，可以做前处理，以消除背景噪音。 </li></ol>在相邻的图像，它可以是多种多样的大小和形状的影响相关的窗口之间进行相互相关。交叉相关性后，可以做图像后处理，删除错误向量或离群。 不同的可用选项及其精度的详细描述，可以发现在皮茨等人 （2012B），最好的处理血液被认为是"图像重叠"与窗口长度延长的方法，与流。这些操作可以像MATLAB程序中手动完成，或在您的系统软件包。该<html>软件并不重要，更重要的是背后的数学操作，每个操作可以影响最终速度的档案的准确性。 由此产生的向量在空间可被平均在整个信道取得瞬时速度分布，然后时刻再次平均，得到的平均的，有代表性的速度分布图。 kloosterman 等人（2011）得到大景深的μPIV测量中的错误的解释。这里介绍的数据处理错误的讨论中可以找到皮茨等人（2012B）的脉冲测量和Chayer 等人 （2012）的高速测量。 速度分布的实例列于图3和图4，图3给出一个单一的速度剖面的中心线10微升/小时流量的RBC在H = 10，在140μm宽的信道。 帐篷"这种单一的配置文件来实现的平均值在整个信道的相关的载体，得到的速度分布，然后取平均值得到有代表性的测量时间，在这种情况下，100对整个视场的时间的平均值。 水标定流量与编程为30微升/小时的流速在100平方微米的信道的三维重建轮廓的一个例子，在图4中找到。在图4中 ，以1微米的间隔测量的档案。 <ol start="10"><li>可选:在所描绘的高速图像设置可以在相同条件下通过切换摄像机（和数据采集系统）。用于可视化的无细胞层中的信道，并用于定量聚合，这可能是有用的。数据分析是略有不同的（Chayer， 等人，2012）。 </li></ol>白光图像与无红细胞聚集预选在图5中，与指向H = 20。最佳的图像显示H = 20除去的红细胞聚集的能力，在PBS中，在1微升/小时。底部图像是原生0.5微升/小时血浆H = 20。 ，聚集在底部的图像是可见的。 <ol start="11"><li>关闭系统时，以安全的方式测量已完成。使用适当的激光安全程序，直到完全关闭激光电源。 </li></ol>

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什么都没有透露。

使用μPIV规模的微循环血流量测量可以洞察到了大量的有关生物医药，机械和化工过程。部分的关键因素考虑到红细胞本身，红细胞聚集或运动的荧光微粒的聚集和变形性，和在通道中的RBC的沉降密度。所有这些都可以被占，则一般遵循上述指引。有一个基本的清单，要记住，使用这个系统的良好的测量。首先，确定有多少合规系统或建议系统。为了尽量减少遵守使用油管可能在最短的和尽可能?...

人体中含有许多血管直径小于50微米，这是主要的血液和组织之间的交流网站。这些血管的血流量的研究表示一个相当大的挑战，由于规模测量的血液的流体性质。这些测量值，包括在小动脉和小静脉的压力梯度，在墙上的剪切速度分布，是与生理反应的关键因素。现在有前所未有的机遇，以解决这些测量挑战，由于新的实验技术，在微观尺度上，研究了微循环和解决这一多尺度问题。 微观粒子的图像测速（μPIV）是一个基于粒子的流量可视化技术，用于评估血液流动的速度分布在微通道通过交叉相关。 μPIV，首先圣地亚哥等人开发的，已用于与血液流变学自杉井等人的研究，在2001年使用的手法是在100μm的圆形的玻璃管1,2测量血流量。不同的方法μPIV存在。可以使用高速摄像机相关联的运动的红血细胞（红细胞），脉冲的图片可被用来示踪粒子的运动相关联。这些选项可以配上直立或倒置显微镜，根据不同的应用。在这两种情况下，其结果是一个二维速度分布图。另一种方法是使用激光共聚焦显微镜实现2D和3D的配置文件。这种方法已被应用到血液3,4,5。 微观尺度PIV有多种并发症较宏观PIV。位宏PIV中的数据可以被限制为一个单一的平面的光通过片材，但在微观尺度上卷照明是必要的。卷照明成像微血流量是一个更大的问题，如红细胞本身相比要大的channels，使用的红细胞作为示踪粒子导致的深度的相关性（DOC），它可以显着降低的准确性的互相关结果6,7,8。继Wereley 等人（1998年）为40微米高的通道与RBC作为示踪剂的DOC是8.8微米，1微米示踪粒子DOC是6.7微米。改变通道高度和放大倍率时，这种差异变得更加明显。此外，红细胞是不透明的，并在流动的红细胞的密度增加会导致成像的困难。荧光示踪粒子，在第一圣地牙哥等人（1998）所使用的，已被作为一种工具，以减少聚焦粒子的影响，倡导使用尽可能最小的颗粒。使用直径为1微米的荧光的微粒用激光耦合的一种方法，可能会降低微血流显像10的深度的焦点问题。有几个当前的状态μPIVTEC评论的hnology，其中每一个突出的重要性μPIV血流研究11,12。几个重要的考虑，必须考虑到当使用血液μPIV。在微观层面上，改善微循环规模，血液可以不被认为是均匀的流体，因为是悬挂灵活的红血细胞（红细胞），大型白细胞，血小板及其他蛋白质悬浮在一个牛顿流体（血浆） 。 的速度分布测量信号可以用来测量微血流量的某些特性。的重要因素在microhemorheology是血液的流速的速度剖面的形状，容器的壁处的剪切应力。此信息具有临床意义，，改善微循环是网站在体内的养分交换，这种交换是剪切速率依赖。有几个目前的审查研究的微循环状态的研究，以及13，14,15。 这里介绍的是μPIV血流量测量中的聚二甲基硅氧烷（PDMS）微通道的协议。按照本协议第1条中的来源渠道，在内部制造PDMS。获得认可的屠宰场猪血液样本和清理后，该协议的第2条。使用LaVision MITAS的μPIV系统，该协议第3条中所描述的所有数据。设置包括一个Nd:YAG激光（新浪潮研究，美国）和CCD照相机（图像激烈，Lavision）由一个可编程触发单元，在荧光显微镜加上3轴载物台移动中，和一台计算机控制的，除了到一个高速照相机（1M150 Dalsa公司，荷兰）溶液中加入红细胞本身的可视化。这两款相机连接到2端口光纤盒（德国蔡司定制）。在典型的在体内的血流量测量，直立的显微镜是用来跟踪的红细胞mselves，而在典型的体外应用倒置显微镜是用来跟踪示踪粒子。在这个独特的双重设置，允许两个示踪剂使用倒置显微镜成像光学框。通过高精密注射器泵的微芯片（Nexus3000，Chemyx公司，美国）被引入到血液。该系统示于图1中 ，图中的顶部部分表示为140μm，40μm的矩形通道的PDMS制作的图表，和底部代表整个系统，包括摄像机，激光，注射泵和显微镜。 电流μPIV集起坐，通常与专有软件，包括TSI，丹特克动力，LaVision。标准的交叉相关算法可以通过众多的软件选项，包括MATLAB的实现。该软件是不是关键，了解的对话方块对应以数学将成为使用ŗ好得多。在这个协议中戴维斯，LaVision的专有软件或MATLAB利用。此协议是不特定的软件，但菜单选项可能会在不同的地方，不同的软件包。

<table><tbody><tr><td>poly(dimethylsiloxane) (PDMS), &lt;em&gt;i.e.&lt;/em&gt; Sylgard-184</td><td>Dow-Corning</td><td>3097358-1004</td><td></td></tr><tr><td>ethylenediaminetetraacetic acid (EDTA)</td><td>Sigma Aldrich</td><td>E9884-100G</td><td></td></tr><tr><td>poshpate buffered saline (PBS)</td><td>Sigma Aldrich</td><td>P5368-10PAK</td><td></td></tr><tr><td>fluorescing micro particles</td><td>Microgenics/FisherSci</td><td>R900</td><td></td></tr><tr><td>glycerol (OPTIONAL)</td><td>Sigma Aldrich</td><td>G6279-500 ml</td><td></td></tr><tr><td>microcentrifuge, &lt;em&gt;i.e.&lt;/em&gt; CritSpin</td><td>FisherSci</td><td>22-269-291</td><td></td></tr><tr><td>syringe, &lt;em&gt;i.e.&lt;/em&gt; 50 &amp;mu;l Gastight</td><td>Hamilton</td><td>80965</td><td></td></tr><tr><td>camera, &lt;em&gt;i.e.&lt;/em&gt; Imager Intense, high speed</td><td>LaVision, Dalsa</td><td>Imager Intense</td><td></td></tr><tr><td>microscope, &lt;em&gt;i.e.&lt;/em&gt; MITAS</td><td>LaVision</td><td>MITAS</td><td></td></tr><tr><td>Nd:YAG laser</td><td>New Wave Research</td><td>Solo-II</td><td></td></tr><tr><td>syringe pump, &lt;em&gt;i.e.&lt;/em&gt; Nexus3000</td><td>Chemyx, Inc.</td><td>Nexus-3000</td><td></td></tr><tr><td>flexible tubing, &lt;em&gt;i.e.&lt;/em&gt; Tygon</td><td>FisherSci</td><td>14-169-1A</td><td></td></tr><tr><td>data processing software, &lt;em&gt;i.e.&lt;/em&gt; DaVis</td><td>LaVision</td><td>DaVis</td><td></td></tr><tr><td>centrifuge, &lt;em&gt;i.e.&lt;/em&gt; Thermo Scientific CL2</td><td>Thermo Scientific</td><td>004260F</td><td></td></tr></tbody></table>

micro-particle image velocimetry for velocity profile measurements of micro blood flows

微观粒子图像测速（μPIV）是用于可视化成对的图片，接种在血液流动的微颗粒。图像互相关，给出一个准确的流速剖面。一个协议为μPIV测量血流量在微。规模的微循环，血液不能被认为是一种均匀的流体，因为它是一个灵活的粒子悬浮液悬浮在血浆中，牛顿流体。从这些测量中，可以推导出剪切速率下，最大速度，速度分布图的形状，和流速。如震源深度，粒子浓度，系统符合的几个关键参数，随着各种血细胞比容和流量条件下的实施例和代表性的结果，以确保准确的，有用的数据。

在所有的数字中，流是左到右的原始图像，并在计算速度剖面向上。与血液血细胞比容H = 10以10微升/小时的流动获得的原始数据，例如， 如图2所示。上游的数据可能会被交叉没有任何的数据处理，以实现速度分布密切相关。皮茨， 等人，（2012B）的前处理和数据处理方法的影响进行了讨论。 = 10和10微升/小时的流速得到的速度分布图，从与图2相似在hematorcrit H的数...

Watch this Scientific Journal Video about Micro-particle Image Velocimetry for Velocity Profile Measurements of Micro Blood Flows at JoVE.com

Micro-particle Image Velocimetry for Velocity Profile Measurements of Micro Blood Flows

微观粒子图像测速（μPIV）是用来配对接种于血流量，给出一个准确的流速剖面互相关微颗粒的图像可视化。剪切速率下，最大速度，速度分布图的形状，和流速，每个都具有临床应用，可以是来自于这些测量。

微观粒子图像测速技术，微血液流动的速度剖面测量

Micro-particle image velocimetry (&mu;PIV) is used to visualize paired images of micro particles seeded in blood flows. The images are cross-correlated to ...

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17.2K 次观看.  University of Ottawa. 微观粒子图像测速（μPIV）是用来配对接种于血流量，给出一个准确的流速剖面互相关微颗粒的图像可视化。剪切速率下，最大速度，速度分布图的形状，和流速，每个都具有临床应用，可以是来自于这些测量。

视频: Micro-particle Image Velocimetry for Velocity Profile Measurements of Micro Blood Flows

Echo Particle Image Velocimetry

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 Consequently, a prerequisite for understanding, predicting, and controlling fluid flows is the capability to measure the velocity field with adequate spatial and temporal resolution.2 For velocity measurements in optically opaque fluids or through optically opaque geometries, echo particle image velocimetry (EPIV) is an attractive diagnostic technique to generate "instantaneous" two-dimensional fields of velocity.3,4,5,6 In this paper, the operating protocol for an EPIV system built by integrating a commercial medical ultrasound machine7 with a PC running commercial particle image velocimetry (PIV) software8 is described, and validation measurements in Hagen-Poiseuille (i.e., laminar pipe) flow are reported.
For the EPIV measurements, a phased array probe connected to the medical ultrasound machine is used to generate a two-dimensional ultrasound image by pulsing the piezoelectric probe elements at different times. Each probe element transmits an ultrasound pulse into the fluid, and tracer particles in the fluid (either naturally occurring or seeded) reflect ultrasound echoes back to the probe where they are recorded. The amplitude of the reflected ultrasound waves and their time delay relative to transmission are used to create what is known as B-mode (brightness mode) two-dimensional ultrasound images. Specifically, the time delay is used to determine the position of the scatterer in the fluid and the amplitude is used to assign intensity to the scatterer. The time required to obtain a single B-mode image, t, is determined by the time it take to pulse all the elements of the phased array probe. For acquiring multiple B-mode images, the frame rate of the system in frames per second (fps) = 1/&delta;t. (See 9 for a review of ultrasound imaging.)
For a typical EPIV experiment, the frame rate is between 20-60 fps, depending on flow conditions, and 100-1000 B-mode images of the spatial distribution of the tracer particles in the flow are acquired. Once acquired, the B-mode ultrasound images are transmitted via an ethernet connection to the PC running the PIV commercial software. Using the PIV software, tracer particle displacement fields, D(x,y)[pixels], (where x and y denote horizontal and vertical spatial position in the ultrasound image, respectively) are acquired by applying cross correlation algorithms to successive ultrasound B-mode images.10 The velocity fields, u(x,y)[m/s], are determined from the displacements fields, knowing the time step between image pairs, &Delta;T[s], and the image magnification, M[meter/pixel], i.e., u(x,y) = MD(x,y)/&Delta;T. The time step between images &Delta;T = 1/fps + D(x,y)/B, where B[pixels/s] is the time it takes for the ultrasound probe to sweep across the image width. In the present study, M = 77[&mu;m/pixel], fps = 49.5[1/s], and B = 25,047[pixels/s]. Once acquired, the velocity fields can be analyzed to compute flow quantities of interest.

An echo particle image velocimetry (EPIV) system capable of acquiring two-dimensional fields of velocity in optically opaque fluids or through optically opaque geometries is described, and validation measurements in pipe flow are reported.

回声粒子图像测速技术

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 ...

科研

工程学

High-speed Particle Image Velocimetry Near Surfaces

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. 
Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (&gt; 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows.
A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included.

A procedure for studying transient flows near boundaries using high-resolution, high-speed particle image velocimetry (PIV) is described here. PIV is a non-intrusive measurement technique applicable to any optically accessible flow by optimizing several parameter constraints such as the image and recording properties, the laser sheet properties, and analysis algorithms.

表面附近的高速粒子图像测速

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The ...

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a standard fluid dynamic diagnostic, particle image velocimetry (PIV), to measure: i) velocities of individual particles (grains), extant on short, grain-collision time-scales, ii) velocities of systems of particles, on both short collision-time- and long, continuum-flow-time-scales, iii) collective hydrodynamic modes known to exist in dense molecular fluids, and iv) short- and long-time-scale velocity autocorrelation functions, central to understanding particle-scale dynamics in strongly interacting, dense fluid systems. The basic system is composed of an imaging system, light source, vibrational sensors, vibrational system with a known media, and PIV and analysis software. Required experimental measurements and an outline of the theoretical tools needed when using the analog technique to study molecular-scale hydrodynamic processes are highlighted. The proposed technique provides a relatively straightforward alternative to photonic and neutron beam scattering methods traditionally used in molecular hydrodynamic studies.

An experimentally accessible analog method for studying molecular hydrodynamic processes in dense fluids is presented. The technique uses particle image velocimetry of vibrated, high-restitution grain piles and allows direct, macroscopic observation of dynamical processes known and predicted to exist in strongly interacting, high density gases and liquids.

一种研究稠密气体和液体分子流体力学过程的模拟宏观技术

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a ...

Controlled Microfluidic Environment for Dynamic Investigation of Red Blood Cell Aggregation

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white blood cells and platelets that are suspended in blood plasma. Due to the abundance of the RBCs (40% to 45% of the blood volume), their behavior dictates the rheological behavior of blood especially in the microcirculation. At very low shear rates, RBCs are seen to assemble and form entities called aggregates, which causes the non-Newtonian behavior of blood. It is important to understand the conditions of the aggregates formation to comprehend the blood rheology in microcirculation. The protocol described here details the experimental procedure to determine quantitatively the RBC aggregates in microcirculation under constant shear rate, based on image processing. For this purpose, RBC-suspensions are tested and analyzed in 120 x 60 &#181;m poly-dimethyl-siloxane (PDMS) microchannels. The RBC-suspensions are entrained using a second fluid in order to obtain a linear velocity profile within the blood layer and thus achieve a wide range of constant shear rates. The shear rate is determined using a micro Particle Image Velocimetry (&#181;PIV) system, while RBC aggregates are visualized using a high speed camera. The videos captured of the RBC aggregates are analyzed using image processing techniques in order to determine the aggregate sizes based on the images intensities.

The protocol described details an experimental procedure to quantify Red Blood Cell (RBC) aggregates under a controlled and constant shear rate, based on image processing techniques. The goal of this protocol is to relate RBC aggregate sizes to the corresponding shear rate in a controlled microfluidic environment.

微流控控制环境的红细胞聚集动态调查

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white ...

生物工程

Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine micro-organisms, and/or sediments in the ocean, or fluidized bed reactors and combustion processes in engineered systems. In order to study the effect of turbulence on the kinematics of particles in such flows, simultaneous measurements of both the flow and particle kinematics are required. Non-intrusive, optical flow measurement techniques for measuring turbulence, or for tracking particles, exist but measuring both simultaneously can be challenging due to interference between the techniques. The method presented herein provides a low cost and relatively simple method to make simultaneous measurements of the flow and particle kinematics. A cross section of the flow is measured using a particle image velocimetry (PIV) technique, which provides two components of velocity in the measurement plane. This technique utilizes a pulsed-laser for illumination of the seeded flow field that is imaged by a digital camera. The particle kinematics are simultaneously imaged using a light emitting diode (LED) line light that illuminates a planar cross section of the flow that overlaps with the PIV field-of-view (FOV). The line light is of low enough power that it does not affect the PIV measurements, but powerful enough to illuminate the larger particles of interest imaged using the high-speed camera. High-speed images that contain the laser pulses from the PIV technique are easily filtered by examining the summed intensity level of each high-speed image. By making the frame rate of the high-speed camera incommensurate with that of the PIV camera frame rate, the number of contaminated frames in the high-speed time series can be minimized. The technique is suitable for mean flows that are predominantly two-dimensional, contain particles that are at least 5 times the mean diameter of the PIV seeding tracers, and are low in concentration.

The technique described herein offers a low cost and relatively simple method to simultaneously measure particle kinematics and turbulence in flows with low particle concentrations. The turbulence is measured using particle image velocimetry (PIV), and particle kinematics are calculated from images obtained with a high-speed camera in an overlapping field-of-view.

流成像技术同时测量湍流和粒子运动学

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine ...

Intravital Video Microscopy Measurements of Retinal Blood Flow in Mice

Alterations in retinal blood flow can contribute to, or be a consequence of, ocular disease and visual dysfunction. Therefore, quantitation of altered perfusion can aid research into the mechanisms of retinal pathologies. Intravital video microscopy of fluorescent tracers can be used to measure vascular diameters and bloodstream velocities of the retinal vasculature, specifically the arterioles branching from the central retinal artery and of the venules leading into the central retinal vein. Blood flow rates can be calculated from the diameters and velocities, with the summation of arteriolar flow, and separately venular flow, providing values of total retinal blood flow. This paper and associated video describe the methods for applying this technique to mice, which includes 1) the preparation of the eye for intravital microscopy of the anesthetized animal, 2) the intravenous infusion of fluorescent microspheres to measure bloodstream velocity, 3) the intravenous infusion of a high molecular weight fluorescent dextran, to aid the microscopic visualization of the retinal microvasculature, 4) the use of a digital microscope camera to obtain videos of the perfused retina, and 5) the use of image processing software to analyze the video. The same techniques can be used for measuring retinal blood flow rates in rats.

Intravital microscopy can be used in animals to visualize and measure retinal vascular diameters, bloodstream velocities, and total retinal blood flow.

视网膜血流小鼠活体视频显微镜测量

Alterations in retinal blood flow can contribute to, or be a consequence of, ocular disease and visual dysfunction. Therefore, quantitation of altered ...

医学

A Microfluidic Model of Biomimetically Breathing Pulmonary Acinar Airways

Quantifying respiratory flow characteristics in the pulmonary acinar depths and how they influence inhaled aerosol transport is critical towards optimizing drug inhalation techniques as well as predicting deposition patterns of potentially toxic airborne particles in the pulmonary alveoli. Here, soft-lithography techniques are used to fabricate complex acinar-like airway structures at the truthful anatomical length-scales that reproduce physiological acinar flow phenomena in an optically accessible system. The microfluidic device features 5 generations of bifurcating alveolated ducts with periodically expanding and contracting walls. Wall actuation is achieved by altering the pressure inside water-filled chambers surrounding the thin PDMS acinar channel walls both from the sides and the top of the device. In contrast to common multilayer microfluidic devices, where the stacking of several PDMS molds is required, a simple method is presented to fabricate the top chamber by embedding the barrel section of a syringe into the PDMS mold. This novel microfluidic setup delivers physiological breathing motions which in turn give rise to characteristic acinar air-flows. In the current study, micro particle image velocimetry (&#181;PIV) with liquid suspended particles was used to quantify such air flows based on hydrodynamic similarity matching. The good agreement between &#181;PIV results and expected acinar flow phenomena suggest that the microfluidic platform may serve in the near future as an attractive in vitro tool to investigate directly airborne representative particle transport and deposition in the acinar regions of the lungs.

Soft-lithography was utilized to produce a representative true-scale model of pulmonary alveolated airways that expand and contract periodically, mimicking physiological breathing motion. This platform recreates respiratory acinar flows on a chip, and is anticipated to facilitate experimental investigation of inhaled aerosol dynamics and deposition in the pulmonary acinus.

仿生的微流体模型肺呼吸腺泡航空公司

Quantifying respiratory flow characteristics in the pulmonary acinar depths and how they influence inhaled aerosol transport is critical towards ...

Meso-Scale Particle Image Velocimetry Studies of Neurovascular Flows In Vitro

Particle image velocimetry (PIV) is used in a wide variety of fields, due to the opportunity it provides for precisely visualizing and quantifying flows across a large spatiotemporal range. However, its implementation typically requires the use of expensive and specialized instrumentation, which limits its broader utility. Moreover, within the field of bioengineering, in vitro flow visualization studies are also often further limited by the high cost of commercially sourced tissue phantoms that recapitulate desired anatomical structures, particularly for those that span the mesoscale regime (i.e., submillimeter to millimeter length scales). Herein, we present a simplified experimental protocol developed to address these limitations, the key elements of which include 1) a relatively low-cost method for fabricating mesoscale tissue phantoms using 3-D printing and silicone casting, and 2) an open-source image analysis and processing framework that reduces the demand upon the instrumentation for measuring mesoscale flows (i.e., velocities up to tens of millimeters/second). Collectively, this lowers the barrier to entry for nonexperts, by leveraging resources already at the disposal of many bioengineering researchers. We demonstratethe applicability of this protocol within the context of neurovascular flow characterization; however, it is expected to be relevant to a broader range of mesoscale applications in bioengineering and beyond.

Meso-Scale Particle Image Velocimetry Studies of Neurovascular Flows In Vitro

Here we present simplified methods for fabricating transparent neurovascular phantoms and characterizing the flow therein. We highlight several important parameters and demonstrate their relationship to field accuracy.

神经血管流动的中尺度粒子图像测速研究

Particle image velocimetry (PIV) is used in a wide variety of fields, due to the opportunity it provides for precisely visualizing and quantifying flows ...

Spatial Temporal Analysis of Fieldwise Flow in Microvasculature

Changes in blood flow velocity and distribution are vital in maintaining tissue and organ perfusion in response to varying cellular needs. Further, appearance of defects in microcirculation can be a primary indicator in the development of multiple pathologies. Advances in optical imaging have made intravital microscopy (IVM) a practical approach, permitting imaging at the cellular and subcellular level in live animals at high-speed over time. Yet, despite the importance of maintaining adequate tissue perfusion, spatial and temporal variability in capillary flow is seldom documented. In the standard approach, a small number of capillary segments are chosen for imaging over a limited time. To comprehensively quantify capillary flow in an unbiased way we developed Spatial Temporal Analysis of Fieldwise Flow (STAFF), a macro for FIJI open-source&#160;image analysis software. Using high-speed image sequences of full fields of blood flow within capillaries, STAFF produces&#160;images that represent motion over time called kymographs for every time interval for every vascular segment. From the kymographs STAFF calculates velocities from the distance that red blood cells move over time, and outputs the velocity data as a sequence of color-coded spatial maps for visualization and tabular output for quantitative analyses. In normal mouse livers, STAFF analyses quantified profound differences in flow velocity between pericentral and periportal regions within lobules. Even more unexpected are the differences in flow velocity seen between sinusoids&#160;that are side by side and fluctuations seen within individual vascular segments over seconds. STAFF is a powerful new tool capable of providing novel insights by enabling measurement of the complex spatiotemporal dynamics of capillary flow.

To quantify microvascular flow from high speed capillary flow image sequences, we developed STAFF (Spatial Temporal Analysis of Fieldwise Flow) software. Across the full image field and over time, STAFF evaluates flow velocities and generates a sequence of color-coded spatial maps for visualization and tabular output for quantitative analyses.

微血管中场流的空间时间分析

Changes in blood flow velocity and distribution are vital in maintaining tissue and organ perfusion in response to varying cellular needs. Further, ...

Blood Flow Imaging with Ultrafast Doppler

The pulsed-Doppler effect is the main technique used in clinical echography to assess blood flow. Applied with conventional focused ultrasound Doppler modes, it has several limits. Firstly, a finely tuned signal filtering operation is needed to distinguish blood flows from surrounding moving tissues. Secondly, the operator must choose between localizing the blood flows or quantifying them. In the last two decades, ultrasound imaging has undergone a paradigm shift with the emergence of ultrafast ultrasound using unfocused waves. In addition to a hundredfold increase in framerate (up to 10000 Hz), this new technique also breaks the conventional quantification/localization trade-off, offering a complete blood flow mapping of the field of view and a simultaneous access to fine velocities measurements at the single-pixel level (down to 50 &#181;m). This data continuity in both spatial and temporal dimensions strongly improves the tissue/blood filtering process, which results in an increase sensitivity to small blood flow velocities (down to 1 mm/s). In this method paper, we aim to introduce the concept of ultrafast Doppler as well as its main parameters. Firstly, we summarize the physical principles of unfocused wave imaging. Then, we present the Doppler signal processing main steps. Particularly, we explain the practical implementation of the critical tissue/blood flow separation algorithms and on the extraction of velocities from these filtered data. This theoretical description is supplemented by in vitro experiences. A tissue phantom embedding a canal with flowing blood-mimicking fluid is imaged with a research programmable ultrasound system. A blood flow image is obtained and the flow characteristics are displayed for several pixels in the canal. Finally, a review of in vivo applications is proposed, showing examples in several organs such as carotids, kidney, thyroid, brain and heart.

This protocol shows how to apply ultrafast ultrasound Doppler imaging to quantify blood flows. After a 1 s long acquisition, the experimenter has access to a movie of the full field of view with axial velocity values for each pixel every &#8776;0.3 ms (depending on the ultrasound time of flight).

血流成像与超快多普勒

The pulsed-Doppler effect is the main technique used in clinical echography to assess blood flow. Applied with conventional focused ultrasound Doppler ...