Name: blood flow imaging with ultrafast doppler
Uploaded: 2020-10-14T13:00:00.000+00:00
Duration: 5 min 57 s
Description: Watch this Scientific Journal Video about Blood Flow Imaging with Ultrafast Doppler at JoVE.com

我们要感谢什雷亚·沙阿的校对和建议。

1. 多普勒幻影准备设置 （图 2A）
<ol><li>将腹腔泵、血液模拟液库、脉搏阻尼器和多普勒流幻影与塑料管连接起来。</li>
	<li>选择直径为 4 mm 的运河。</li>
	<li>将泵编程为弹出 720 mL/min 的液体 0.3 秒，然后弹出 50 mL/min 的 0.7 秒，分别模拟晶体和硅藻心脏相位</li>
	<li>运行泵并轻轻摇动管道以排出潜在的气泡。 注意:操作员可以选择不同的运河直径和不同的泵速率，但必须确保超声波序列足够快，以获得最快的流速。稍后提交的 Eq. 3 有助于设计序列。</li>
</ol>2. 超高速超声波扫描仪设置 （图 2A）
<ol><li>将支持超快的研究扫描仪与主机连接起来，并连接 PCI 快速链接。</li>
	<li>更改超声波扫描仪上的传感器适配器以匹配探头连接器，然后连接探头。</li>
	<li>运行 Matlab 并激活超声波扫描仪许可证。 注:本节及以下部分含蓄地假设使用威拉索尼奇万塔奇系统。</li>
</ol>3. 超声序列编程
<ol><li>使用示例脚本，设计用于探头定位的传统聚焦"B 模式"（即 echx）序列。<ol>
<li>将成像深度设置为 50 mm。</li>
		<li>将焦距深度设置为 35 mm。</li>
	</ol>
</li>
	<li>使用示例脚本，设计超快超声序列。<ol>
<li>将成像深度设置为 50 mm。</li>
		<li>程序 3 倾斜平面波在 [-3，0，3] 度。</li>
		<li>将脉冲重复频率 （PRF） 设置为 12 kHz。</li>
		<li>使用 4 个半周期进行超声波形式，中心频率取决于所使用的探头。此处假定中心频率为 5.2 MHz。</li>
		<li>将总持续时间设置为 1 s。</li>
	</ol>
</li>
</ol>4. 探头定位和数据采集
<ol><li>在探头的镜头上涂抹超声波凝胶。</li>
	<li>将探针放在幻影上，并启动B模式超声波序列。</li>
	<li>找到感兴趣的运河。液体看起来比周围的组织暗。将探头置于纵向视图中。</li>
	<li>手动将探头保持在感兴趣的位置。</li>
	<li>结束 B 模式序列并启动超快序列获取脚本。</li>
</ol>5. 图像重建 （图 2B）
<ol><li>序列结束后，保存原始数据（也称为射频数据"RF"）。</li>
	<li>使用超声波系统默认软件启动图像重建脚本。在过程结束时，应创建智商数据矩阵。 注:超声波回声记录在探头的每个元素和每个发射/接收，然后存储在 RF 数据矩阵中。图像重建将适当的延迟法应用于每个通道，并导致所谓的"IQ"（阶段/四重）矩阵。复杂的智商矩阵有三个维度:两个用于空间（图像深度和宽度），一个用于时间</li>
</ol>6. 杂乱无章的过滤 （图 2C）
注:有关步骤 6-7，请参阅 补充材料中提供的 Matlab 脚本。
<ol><li>将 3D（空间 x 空间 x 时间）智商矩阵重塑为 2D（空间 x 时间）卡索拉蒂矩阵，名为 IQr。</li>
	<li>计算 IQr 的奇数值分解15 （Eq. 1）。 <img alt="Equation 1" src="/files/ftp_upload/61838/61838equ01v3.jpg"> Eq. 1</li>
	<li>使用巴兰格等人描述的空间单向向量 U计算空间 相似性矩阵 C（II、D），并识别血液亚空间边界 N。</li>
	<li>使用此截止 N 来筛选德梅内等人15 （II，C） 中描述的智商数据。</li>
</ol>7. 流量可视化和速度测量 （图 2C）
<ol><li>通过沿时间维度（Eq.2）集成过滤数据 IQt 的信封来计算功率多普勒地图PD。3D 坐标 z、x 和 t 分别是深度、宽度和时间维度 ，nt 和获得的帧数。 <img alt="Equation 2" src="/files/ftp_upload/61838/61838equ02v5.jpg"> Eq. 2</li>
	<li>以对数比例显示PD地图。要设置动态范围，请计算运河外区域的平均 PD，并将 dB 中的此值用作动态范围的下界值。一个典型的动态范围是[-30，0]dB。</li>
	<li>在图像上定义包含 1 到 30 像素的圆形兴趣区域 （ROI）。</li>
	<li>平均 智商f 信号超过该 ROI 的像素，以获得 <img alt="Equation 3" src="/files/ftp_upload/61838/61838equ03v2.jpg"> nt 时间点的矢量。</li>
	<li><img alt="Equation 4" src="/files/ftp_upload/61838/61838equ04v2.jpg">使用短时间傅立刚变换 （STFT） 的平方级计算和显示多普勒光谱。<ol>
<li>将 STFT 窗口设置为 60 个样本的汉恩窗口。</li>
		<li>将STFT重叠设置为窗口长度的90%。</li>
	</ol>
</li>
	<li>在光谱图的每个时间点叠加中心频率。</li>
	<li>使用多普勒公式（Eq.3）将频率f值转换为血液轴向速度vz。c0是介质中的声音速度，fTW是传输超声波形的中心频率（此处为 5.2 MHz）。 <img alt="Equation 5" src="/files/ftp_upload/61838/61838equ05v4.jpg"> Eq. 3</li>
</ol>

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硬件问题 如果用户提供其自定义主机，主板和计算机的情况必须有一个可用的PCI快递插槽。CPU 还必须有足够的 PCIe 通道来处理所有设备。
探头选择 超声波探头（也称为传感器）是根据所需的空间分辨率和视场的几何形状选择的。探头的中心频率越高，空间分辨率越高，但成像深?...

超声成像是临床实践和研究活动中最常用的成像技术之一。生物组织中超声波发射与后散射回波记录相结合，可以重建解剖图像，即所谓的"B模式"。这种方法完全适用于软组织成像，如生物组织，通常允许超声波穿透几厘米以上，传播速度为≈1540m/s。根据超声波探头的中心频率，可获得分辨率从 30μm 到 1 mm 的图像。此外，众所周知，声源的运动会影响相关波的物理特性。特别是，波相对于其源速的频率变化之间的联系被描述为多普勒效应1，其最简单的表现是移动救护车的警报器的音调变化。超声成像长期以来一直利用这种物理效应来观察移动中的红血球2，并提出了各种通常称为"多普勒成像"的成像模式。这些模式能够评估血液流动在非常不同的应用和器官，如大脑，心脏，肾脏或周围动脉。
值得注意的是，目前大多数可用的超声波系统都依赖于同样的技术，即传统的超声波。基本原理如下:声束使视野发音，并沿着超声波传感器孔径扫射。对于光束的每个位置，回声都会被记录下来并转换成最终图像的行。通过沿传感器逐步移动光束，整个视场可以按线成像（图 1，左面板）。这一战略很好地适应了21世纪初一直存在的电气限制和计算能力。尽管如此，它还是有几个缺点。其中，最终帧速率受光束扫描过程限制为每秒几百张图像。在血流量方面，这种相对较低的帧速率会影响可以检测到的最大流速，这是由香农-奈奎斯特3的采样标准决定的。此外，传统的多普勒必须处理复杂的权衡。为了评估特定感兴趣区域（ROI）的血流量速度，必须连续记录来自该投资回报率的几个回声。这意味着超声波束暂时保持在固定位置。回声合奏的时间越长，对投资回报率的速度估计就越好。但是，要生成视场的完整图像，光束必须扫描介质。因此，人们可以感觉到这两个约束之间的冲突:按住光束精确评估一条线的速度，或者移动光束以生成图像。不同的传统多普勒模式（即彩色多普勒或脉冲波多普勒）直接反映了这种权衡。通常，彩色多普勒会生成用于定位船只4的低保真流图，然后使用脉冲波多普勒准确量化先前标识的容器5中的流量。
这两个限制（低帧率和本地化/量化权衡）都通过非常高帧率的新兴技术来克服。其中，合成孔径方法6或多线传输技术可引证7。在这项研究中，我们专注于所谓的超快超声波方法。二十年前推出的8、9、10，这种方法也依赖于超声波的发射/接收，但模式完全不同。事实上，超高速成像不是使用扫描聚焦光束，而是使用平面波或分散波，这些波能够用单个发射来使视野发出共鸣。在单次发射之后，相关电子产品还能够接收和处理来自整个视野的大量回波。最后，图像可以从单个发射/接收模式11（图 1，右面板）进行重建。由于声能的扩散，这些未聚焦的排放可能具有低信号与噪声比 （SNR）。这可以通过发射几个标题的平面波（或不同来源的发散波）和添加由此产生的图像来解决。这种方法被命名为"连贯复合"12。出现了两个主要后果。首先，帧速率仅取决于飞行的超声波时间，可以达到 1 到 10 kHz 的典型值。其次，这确保了空间和时间维度的数据连续性，也称为空间相干性。因此，传统的本地化/量化权衡被打破。这种高帧速率和空间相干性组合对超声波检测血流的能力有着巨大的影响。与传统的超声波相比，超高速超声波提供了血流3的完整特征。实际上，用户可以访问图像中每个像素的速度时间过程，在整个采集过程中（通常为 ≈1 s），其时间刻度由帧速率给出（通常，帧速率为 5 kHz，时间分辨率为 200μs）。这种高帧速率使该方法适合广泛的应用，如快速流动的器官，如心脏室13或心肌与冠状微注14。此外，它已被证明，其空间的一致性强烈地提高了它的能力，分离缓慢的血液流动从背景移动组织，从而增加了对微血管流15的敏感性。这种能力使16号动物和17号动物都能接触到大脑的微血管。
因此，超高速超声波非常适合在各种情况下的图像血流。它仅限于软生物组织，并将受到硬接口（如骨骼或气腔，如肺）的存在的强烈影响。超声波序列物理参数的调整允许研究减速（下降到1毫米/s 11，16）和快速流动（高达几米/s）。空间分辨率和渗透深度之间存在权衡。通常，分辨率为 50 μm，成本为 5 mm 左右。相反，渗透可以扩展到15-20厘米，成本分辨率为1毫米。值得注意的是，大多数超高速扫描仪，如本文中使用的扫描仪，只提供2D图像。
在这里，我们提出了一个简单的协议，引入超快多普勒成像的概念，使用可编程研究超声波扫描仪和多普勒幻象模仿血管（动脉或静脉）嵌入生物组织。

<table><tbody><tr><td>Blood-mimicking fluid</td><td>CIRS Inc, Norfolk, Virginia, USA</td><td>069DTF</td><td></td></tr><tr><td>Doppler flow phantom</td><td>CIRS Inc, Norfolk, Virginia, USA</td><td>ATS523A</td><td></td></tr><tr><td>Matlab</td><td>MathWorks, Natick, Massachusetts, United States</td><td></td><td></td></tr><tr><td>Peristaltic pump / Doppler flow pump</td><td>CIRS Inc, Norfolk, Virginia, USA</td><td>769</td><td>Include tubings and pulse dampener</td></tr><tr><td>Transducer adpter</td><td>Verasonics, Kirkland, Washington, USA</td><td>UTA 408-GE</td><td></td></tr><tr><td>Ultrafast ultrasound research scanner</td><td>Verasonics, Kirkland, Washington, USA</td><td>Vantage 256</td><td></td></tr><tr><td>Ultrasound probe/transducer</td><td>GE Healthcare</td><td>GE 9L-D</td><td></td></tr></tbody></table>

blood flow imaging with ultrafast doppler

脉冲-多普勒效应是临床血液造影中用于评估血流量的主要技术。适用于传统的聚焦超声多普勒模式，它有几个限制。首先，需要微调信号过滤操作，以区分血液流动与周围移动组织。其次，操作者必须在定位血流或量化血流之间做出选择。在过去的二十年里，超声波成像经历了一个范式的转变，超高速超声波的出现使用了未聚焦的波。除了帧速率增加一百倍（高达 10000 赫兹）外，这项新技术还打破了传统的量化/本地化权衡，为视场提供了完整的血流映射，并同时在单像素级别（降至 50μm）获得精细速度测量。这种空间和时间维度的数据连续性有力地改善了组织/血液过滤过程，从而提高了对小血流量速度的敏感度（降至 1 mm/s）。本文旨在介绍超快多普勒的概念及其主要参数。首先，我们总结了无聚焦波成像的物理原理。然后，我们介绍多普勒信号处理的主要步骤。特别是，我们解释关键组织/血流量分离算法的实际实施，以及从这些过滤数据中提取速度。这种理论描述辅之以体外经验。用流动的血液模拟液嵌入运河的组织幻影与研究可编程超声系统进行成像。获得血流图像，并在运河中显示数个像素的流量特征。最后，建议对体内应用进行审查，在若干器官中举例，如胡萝卜素、肾脏、甲状腺、大脑和心脏。

收购和后期处理的质量首先通过目视检查进行评估。运河的形状必须在功率多普勒图像中清晰可见，组织区域必须显得黑暗。如果多普勒信号的功率不限于运河，则可能意味着杂乱的滤波步骤出错（SVD 阈值太低），或者探测器在获取过程中经历了强烈的移动。
目视检查后，对运河内光谱的研究可以提供实验成败的良好信息。光谱图应是片面的（所有值高于或低于零）。如果?...

Watch this Scientific Journal Video about Blood Flow Imaging with Ultrafast Doppler at JoVE.com

Blood Flow Imaging with Ultrafast Doppler

此协议显示如何应用超高速超声多普勒成像来量化血液流动。经过 1 秒的长收购后，实验者可以访问具有轴向速度值的全视野电影，每个像素每≈0.3 毫秒（取决于飞行的超声波时间）。

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 ...

blood-flow-imaging-with-ultrafast-doppler

Research

Education

JoVE Journal

JoVE Core

Electrical Engineering

Anatomy and Physiology

Bioengineering

Unit 1

Sampling

Blood Vessels and Circulation

SCIENTISTS IN ACTION

7.4K 次观看.  The Hospital for Sick Children, PGCRL Research Institute. 此协议显示如何应用超高速超声多普勒成像来量化血液流动。经过 1 秒的长收购后，实验者可以访问具有轴向速度值的全视野电影，每个像素每≈0.3 毫秒（取决于飞行的超声波时间）。

视频: Blood Flow Imaging with Ultrafast Doppler

Doppler Optical Coherence Tomography of Retinal Circulation

Noncontact retinal blood flow measurements are performed with a Fourier domain optical coherence tomography (OCT) system using a circumpapillary double circular scan (CDCS) that scans around the optic nerve head at 3.40 mm and 3.75 mm diameters. The double concentric circles are performed 6 times consecutively over 2 sec. The CDCS scan is saved with Doppler shift information from which flow can be calculated. The standard clinical protocol calls for 3 CDCS scans made with the OCT beam passing through the superonasal edge of the pupil and 3 CDCS scan through the inferonal pupil. This double-angle protocol ensures that acceptable Doppler angle is obtained on each retinal branch vessel in at least 1 scan. The CDCS scan data, a 3-dimensional volumetric OCT scan of the optic disc scan, and a color photograph of the optic disc are used together to obtain retinal blood flow measurement on an eye. We have developed a blood flow measurement software called "Doppler optical coherence tomography of retinal circulation" (DOCTORC). This semi-automated software is used to measure total retinal blood flow, vessel cross section area, and average blood velocity. The flow of each vessel is calculated from the Doppler shift in the vessel cross-sectional area and the Doppler angle between the vessel and the OCT beam. Total retinal blood flow measurement is summed from the veins around the optic disc. The results obtained at our Doppler OCT reading center showed good reproducibility between graders and methods (&lt;10%). Total retinal blood flow could be useful in the management of glaucoma, other retinal diseases, and retinal diseases. In glaucoma patients, OCT retinal blood flow measurement was highly correlated with visual field loss (R2&gt;0.57 with visual field pattern deviation). Doppler OCT is a new method to perform rapid, noncontact, and repeatable measurement of total retinal blood flow using widely available Fourier-domain OCT instrumentation. This new technology may improve the practicality of making these measurements in clinical studies and routine clinical practice.

Total retinal blood flow is measured by Doppler optical coherence tomography and semi-automated grading software.

多普勒光学相干断层扫描视网膜循环

Noncontact retinal blood flow measurements are performed with a Fourier domain optical coherence tomography (OCT) system using a circumpapillary double ...

科研

医学

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

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 give an accurate velocity profile. A protocol is presented for &mu;PIV measurements of blood flows in microchannels. At the scale of the microcirculation, blood cannot be considered a homogeneous fluid, as it is a suspension of flexible particles suspended in plasma, a Newtonian fluid. Shear rate, maximum velocity, velocity profile shape, and flow rate can be derived from these measurements. Several key parameters such as focal depth, particle concentration, and system compliance, are presented in order to ensure accurate, useful data along with examples and representative results for various hematocrits and flow conditions.

Micro-particle image velocimetry (&mu;PIV) is used to visualize paired images of micro particles seeded in blood flows which are cross-correlated to give an accurate velocity profile. Shear rate, maximum velocity, velocity profile shape, and flow rate, each of which has clinical applications, can be derived from these measurements.

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 ...

生物工程

Using Laser Doppler Imaging and Monitoring to Analyze Spinal Cord Microcirculation in Rat

Laser Doppler flowmetry (LDF) is a noninvasive method for blood flow (BF) measurement, which makes it preferable for measuring microcirculatory alterations of the spinal cord. In this article, our goal was to use both Laser Doppler imaging and monitoring to analyze the change of BF after spinal cord injury. Both the laser Doppler image scanner and the probe/monitor were being employed to obtain each readout. The data of LDPI provided a local distribution of BF, which gave an overview of perfusion around the injury site and made it accessible for comparative analysis of BF among different locations. By intensely measuring the probing area over a period of time, a combined probe was used to simultaneously measure the BF and oxygen saturation of the spinal cord, showing overall spinal cord perfusion and oxygen supply. LDF itself has a few limitations, such as relative flux, sensitivity to movement, and biological zero signal. However, the technology has been applied in clinical and experimental study due to its simple setup and rapid measurement of BF.

Here we present a combination of laser Doppler perfusion imaging (LDPI) and laser Doppler perfusion monitoring (LDPM) to measure spinal cord local blood flows and oxygen saturation (SO2), as well as a standardized procedure for introducing spinal cord trauma on rat.

激光多普勒成像与监测在大鼠脊髓微循环分析中的应用

Laser Doppler flowmetry (LDF) is a noninvasive method for blood flow (BF) measurement, which makes it preferable for measuring microcirculatory ...

行为学

A Novel Application of Musculoskeletal Ultrasound Imaging

Ultrasound is an attractive modality for imaging muscle and tendon motion during dynamic tasks and can provide a complementary methodological approach for biomechanical studies in a clinical or laboratory setting. Towards this goal, methods for quantification of muscle kinematics from ultrasound imagery are being developed based on image processing. The temporal resolution of these methods is typically not sufficient for highly dynamic tasks, such as drop-landing. We propose a new approach that utilizes a Doppler method for quantifying muscle kinematics. We have developed a novel vector tissue Doppler imaging (vTDI) technique that can be used to measure musculoskeletal contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities using ultrasound. The goal of this preliminary study was to investigate the repeatability and potential applicability of the vTDI technique in measuring musculoskeletal velocities during a drop-landing task, in healthy subjects. The vTDI measurements can be performed concurrently with other biomechanical techniques, such as 3D motion capture for joint kinematics and kinetics, electromyography for timing of muscle activation and force plates for ground reaction force. Integration of these complementary techniques could lead to a better understanding of dynamic muscle function and dysfunction underlying the pathogenesis and pathophysiology of musculoskeletal disorders.

We describe a new ultrasound-based vector tissue Doppler imaging technique to measure muscle contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities. This approach provides complementary measurements of dynamic muscle function and could lead to a better understanding of mechanisms underlying musculoskeletal disorders.

肌肉骨骼超声成像的一种新应用

Ultrasound is an attractive modality for imaging muscle and tendon  motion during dynamic tasks and can provide a complementary methodological  approach ...

Ultrasound Assessment of Flow-Mediated Dilation of the Brachial and Superficial Femoral Arteries in Rats

Arterial vasodilation to increases in wall shear rate is indicative of vascular endothelial function. In humans, the non-invasive measurement of endothelial function can be achieved by employing the flow-mediated dilation technique, typically performed in the brachial or superficial femoral artery. Briefly, a blood pressure cuff placed distal to an ultrasound probe is inflated to a suprasystolic pressure, which results in limb ischemia. After 5 min of occlusion the cuff is deflated, resulting in reactive hyperemia and increases in wall shear rate that signal vasodilatory molecules to be released from the endothelium eliciting vasodilation. Despite the thousands of studies performing flow-mediated dilation in humans, surprisingly, no studies have performed this technique non-invasively in living rats. Considering the recent shift in focus to translational research, the establishment of guidelines for non-invasive measurement of flow-mediated dilation in rats and other rodents would be extremely valuable. In the following article, a protocol is presented for the non-invasive measurement of flow-mediated dilation in brachial and superficial femoral arteries of rats, as those sites are most commonly measured in humans.

Non-invasive assessment of endothelial function in humans can be determined by the flow-mediated dilation technique. Although thousands of studies have used this technique, no study has performed this technique non-invasively in rats. The following article describes non-invasive measurement of flow-mediated dilation in the brachial and superficial femoral arteries of rats.

肱血流介导的扩张和大鼠股浅动脉超声评估

Arterial vasodilation to increases in wall shear rate is indicative of vascular endothelial function. In humans, the non-invasive measurement of ...

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, ...

A Novel Approach to Overcome Movement Artifact When Using a Laser Speckle Contrast Imaging System for Alternating Speeds of Blood Microcirculation

The laser speckle contrast imager (LSCI) provides a powerful yet simple technique for measuring microcirculatory blood flow. Ideal for blood dynamic responses, the LSCI is used in the same way as a conventional Laser Doppler Imager (LDI). However, with a maximum skin depth of approximately 1 mm, the LSCI is designed to focus on mainly superficial blood flow. It is used to measure skin surface areas of up to 15 cm x 20 cm. The new technique introduced in this paper accounts for alternating speeds of microcirculations; i.e. both slow and fast flow flux measurement using the LSCI. The novel technique also overcomes LSCI&#39;s biggest shortcoming, which is high sensitivity to artifact movement. An adhesive opaque patch (AOP) is introduced for satisfactory recording of microcirculatory blood flow, by subtracting the LSCI signal from the AOP from the laser speckle skin signal. The optimal setting is also defined because the LSCI is most powerful when flux changes are measured relative to a reference baseline, with blood microcirculatory flux expressed as a percentage change from the baseline. These changes may be used for analyzing the status of the blood flow system.

This study introduces a novel technique for the measurement and analysis of alternating speeds of blood microcirculation in a single experiment using a laser speckle contrast imager.

用激光散斑对比成像系统克服运动伪影的新方法血液微循环的交替速度

The laser speckle contrast imager (LSCI) provides a powerful yet simple technique for measuring microcirculatory blood flow. Ideal for blood dynamic ...

Human Fetal Blood Flow Quantification with Magnetic Resonance Imaging and Motion Compensation

Magnetic resonance imaging (MRI) is an important tool for the clinical assessment of cardiovascular morphology and heart function. It is also the recognized standard-of-care for blood flow quantification based on phase contrast MRI. While such measurement of blood flow has been possible in adults for decades, methods to extend this capability to fetal blood flow have only recently been developed.
Fetal blood flow quantification in major vessels is important for monitoring fetal pathologies such as congenital heart disease (CHD) and fetal growth restriction (FGR). CHD causes alterations in the cardiac structure and vasculature that change the course of blood in the fetus. In FGR, the path of blood flow is altered through the dilation of shunts such that the oxygenated blood supply to the brain is increased. Blood flow quantification enables assessment of the severity of the fetal pathology, which in turn allows for suitable&#160;in utero&#160;patient management and planning for postnatal care.
The primary challenges of applying phase contrast MRI to the human fetus include small blood vessel size, high fetal heart rate, potential MRI data corruption due to maternal respiration, unpredictable fetal movements, and lack of conventional cardiac gating methods to synchronize data acquisition. Here, we describe recent technical developments from our lab that have enabled the quantification of fetal blood flow using phase contrast MRI, including advances in accelerated imaging, motion compensation, and cardiac gating.

Here we present a protocol for measuring fetal blood flow rapidly with MRI and retrospectively performing motion correction and cardiac gating.

通过磁共振成像和运动补偿进行人胎儿血流定量

Magnetic resonance imaging (MRI) is an important tool for the clinical assessment of cardiovascular morphology and heart function. It is also the ...

Ultrafast Doppler Ultrasound for Hepatic Microvasculature Analysis in Mice

Imaging and Quantification of the Hepatic Vasculature of Mice Using Ultrafast Doppler Ultrasound

Non-invasive in vivo imaging of the vasculature is a powerful tool for studying disease mechanisms in rodents. To achieve high sensitivity imaging of the microvasculature using Doppler ultrasound methods, imaging modalities employing the concept of ultrafast imaging are preferred. By increasing the frame rate of the ultrasound scanner to thousands of frames per second, it becomes possible to improve the sensitivity of the blood flow down to 2 mm/s and to obtain functional information about the microcirculation in comparison to a sensitivity of around 1 cm/s in conventional Doppler modes. While Ultrafast Doppler ultrasound (UFUS) imaging has become adopted in neuroscience, where it can capture brain activity through neurovascular coupling, it presents greater challenges when imaging the vasculature of abdominal organs due to larger motions linked to breathing. The liver, positioned anatomically under the diaphragm, is particularly susceptible to out-of-plane movement and oscillating respiratory motion. These artifacts not only adversely affect Doppler imaging but also complicate the anatomical analysis of vascular structures and the computation of vascular parameters. Here, we present a qualitative and quantitative imaging analysis of the hepatic vasculature in mice by UFUS. We identify major anatomical vascular structures and provide graphical illustrations of the hepatic macroscopical anatomy, comparing it to an in-depth anatomical assessment of the hepatic vasculature based on Doppler readouts. Additionally, we have developed a quantification protocol for robust measurements of hepatic blood volume of the microvasculature over time. To contemplate further research, qualitative vascular analysis provides a comprehensive overview and suggests a standardized terminology for researchers working with mouse models of liver disease. Furthermore, it offers the opportunity to apply ultrasound as a non-invasive complementary method to inspect hepatic vascular defects in vivo and measure functional microvascular alterations deep within the organ before unraveling blood vessel anomalies at the micron scale levels using ex vivo staining on tissue sections.

Ultrafast Doppler ultrasound (UFUS) with high spatial resolution (100 &#956;m) and sensitivity represents a suitable noninvasive imaging modality for obtaining a comprehensive qualitative overview of the hepatic vasculature. UFUS also facilitates quantitative measurements of the microvasculature, aiming to enhance our understanding of vascular disease mechanisms.

Non-invasive in vivo imaging of the vasculature is a powerful tool for studying disease mechanisms in rodents. To achieve high sensitivity imaging of the ...

Deep Vascular Imaging in the Eye with Flow-Enhanced Ultrasound

The retina within the eye is one of the most energy-demanding tissues in the body and thus requires high rates of oxygen delivery from a rich blood supply. The capillary lamina of the choroid lines the outer surface of the retina and is the dominating source of oxygen in most vertebrate retinas. However, this vascular bed is challenging to image with traditional optical techniques due to its position behind the highly light-absorbing retina. Here we describe a high-frequency ultrasound technique with subsequent flow-enhancement to image deep vascular beds (0.5-3 cm) of the eye with a high spatiotemporal resolution. This non-invasive method works well in species with nucleated red blood cells (non-mammalian and fetal animal models). It allows for the generation of non-invasive three-dimensional angiographies without the use of contrast agents, and it is independent of blood flow angles with a higher sensitivity than Doppler-based ultrasound imaging techniques.

We present a non-invasive ultrasound technique for generating three-dimensional angiographies in the eye without the use of contrast agents.

使用流量增强超声进行眼部深层血管成像

The retina within the eye is one of the most energy-demanding tissues in the body and thus requires high rates of oxygen delivery from a rich blood ...