Name: phase contrast magnetic resonance imaging in the rat common carotid artery
Uploaded: 2018-09-05T15:30:00.000+00:00
Duration: 7 min 2 s
Description: Watch this Scientific Journal Video about Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery at JoVE.com

这项工作得到了台湾科学技术部授予的 MOST-105-2314-B-039-044-MY2 的赠款支持。

中国医科大学的机构护理和使用委员会 (IACUC) 批准了所有的程序。
1. 动物准备和监测
<ol><li>在开始进行 MRI 扫描的动物准备之前, 在扫描仪室外留下所有磁性敏感物品, 如钱包、钥匙、信用卡等。</li>
	<li>最初麻醉鼠 (2 月大的雄性大 (SD) 鼠, 280–350 g) 在一个感应箱中使用5% 异氟醚 (ISO) 和氧气 (2 升/分钟) 的混合物, 为3–5分钟, 必要时。</li>
	<li>当动物处于卧位时, 没有对尾巴或脚趾捏的反应, 停止 ISO 管理并将动物转移到扫描室。</li>
	<li>把老鼠放在 MRI 床上, 头先俯卧, 并通过鼻锥装置提供 2-3% ISO 以维持麻醉。</li>
	<li>通过在动物躯干下放置呼吸枕传感器来监测呼吸。</li>
	<li>将传感器连接到呼吸系统, 并检查每分钟40-50 次 (bpm) 的呼吸速率。</li>
	<li>用于电影门控的 PC MRI 采集, 分别在右侧前爪和左后爪上放置一个电极 (图 1a)。</li>
	<li>将心电图 (ECG) 电缆拧在一起。</li>
	<li>使用带有耳棒和咬条的头持有人来保护动物以限制头部运动。</li>
	<li>使用暖空气加热系统或纱布垫保持体温, 而在磁铁。</li>
	<li>确保心电图显示器上的 R 波清晰 (图 1b), 并将该动物放在扫描仪中。没有必要将表面线圈放置在动物颈部的顶端, 因为图像是由卷线圈获取的。</li>
</ol>2. MRI 采集
<ol><li>使用 2–3% ISO 在整个成像过程中保持麻醉。持续监测生理反应, 尽可能保持恒定。</li>
	<li>一旦将动物放置在扫描仪内并继续保持生理稳定, 就开始 MRI 扫描。在本研究中, 使用 7 T 小动物 mri 系统的梯度强度为 630 mT/米, 但其他领域的优势, 小动物 MRI 系统可以使用。</li>
	<li>从 MRI 扫描仪的控制台监视器中选择 "定位器"序列, 并使用任何快速的图像采集序列 (如快速旋转回波) 在所有三方向上获取侦察图像, 以创建冠状、轴向和矢状图像。.这些侦察图像的目的是确定成像平面。</li>
	<li>确保动物头部和颈部的中心位于磁铁的中心。如有必要, 调整动物的位置, 直到达到正确的位置。如果动物被重新定位, 重复扫描以获取侦察图像。</li>
	<li>从 MRI 扫描仪的控制台监控器中选择"飞行时间" 序列, 并首先获得2D 的脑血管造影, 以确定共同国家评估的精确解剖位置。使用以下扫描参数: 重复时间 (TR)/回波时间 (TE) = 22/4.87 ms, 翻转角度 = 90°, 视场 (FOV) = 40 x 40 毫米2, 基体大小 = 256 x 256, 切片厚度0.6 毫米, 与励磁的数量 = 1。 注意: 飞行序列的名称可以是特定于供应商的。用户可以在控制台监视器中插入这些参数。</li>
	<li>确保饱和带是 "on", 并放置在顶部, 以避免干扰静脉信号。 注: 对于饱和带, 它通常带有飞行序列。如果显示器上没有显示饱和带, 请通知服务人员。</li>
	<li>在使用飞行后血管造影定位共同国家评估后, 将 PC MRI 的图像平面对准共同国家评估和定向的中心, 使切片垂直于血流方向 (图 2a)。</li>
	<li>确保呼吸和心电门连接到 mri 系统, 显示显示器计算机上的清晰信号 (图 1b), 并将触发模块设置为 "触发模式" , 从 mri 扫描仪的控制台监视器中 "启动"。</li>
	<li>确认动物的生理反应是稳定的, 然后开始从监控计算机的 PC MRI 扫描 (图 1b)。验证显示器计算机和 MRI 扫描仪的控制台监视器中的门选择是否 "on"。 注: 本研究使用的生理学监测系统由供应商提供。对于大多数动物扫描仪, 都提供了类似的生理监测系统和特定的供应商。</li>
	<li>从 mri 扫描仪的控制台显示器上选择 pc mri 序列序列, 并使用以下参数执行门控 pc mri 扫描: tr = 15.55/4.51 ms (最小 TR 和 TE), 翻转 angle=30°, FOV = 40 x 40 毫米2, 矩阵大小 = 192 x 192, 切片厚度 = 2 毫米, 速度编码 (VENC) = 120 厘米/秒, 带 NEX=8。单向 VENC 是通过平面方向获取的。 注: 扫描时间约为8.5 分钟, 但实际扫描时间可能略有不同的动物由于心脏循环的变化。</li>
	<li>重复步骤2.6–2.9 图像获取如果要将感兴趣的区域更改为共同国家评估中的另一个位置, 例如在分岔4中。</li>
	<li>在扫描完成后, 从扫描仪中取出该动物并将其返回到其恢复笼中。</li>
	<li>用暖气灯保暖动物以保持体温。保持灯至少15厘米远离动物, 以防止过热。</li>
	<li>当动物开始移动并表现出对尾巴或脚趾捏的反应时, 关掉暖气灯。</li>
</ol>3. 数据处理
<ol><li>保存数字成像和医学通讯中的 MRI 数据 (DICOM) 格式或任何其他特定于供应商的格式。生成具有两种类型图像的电影系列: 震级图像 (解剖图像) 和相位图像 (图 2b)。 注意: 在某些扫描仪中, 生成了第三种图像, 它可以是震级图像 x 相图或复数差分 (两种不同速度编码梯度的采集之间的复减法)。第三个映像是依赖于供应商的。</li>
	<li>预处理图像数据。将相位图像隐蔽到速度图中, 并更正相位偏移误差5。 注意: 相位图像有一个任意的 mr 单位的信号强度, 而不是真正的速度值, 但 mr 信号强度是线性比例的速度。相位图像的最大 MRI 信号通常被指定为 VENC 的值, 最小信号被分配为 VENC 的相对值。有关 Matlab 脚本的示例, 请参见补充代码文件 1, 然后按 "运行" 按钮。</li>
	<li>通过跟踪共同国家评估的边界, 仔细地描绘 ROI。当动脉在不同的心脏阶段可以扩张和构造时, 为每个时间框架描绘 ROIs。通过对动脉 ROI (即速度 x 区域) 的积分来计算血流量。结果每个动脉的血流都在毫升/秒的单位内。有关 Matlab 脚本的示例, 请参见补充代码文件 2, 然后按 "运行" 按钮。</li>
</ol>

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没有什么可透露的。

MRI 是一种非侵入性和纵向评价血流的综合方法。本文提出了一种用于大鼠共同评价的 PC 磁共振成像的协议。本程序易于在任何动物 MRI 扫描仪中执行, 并显示良好的重现性。
PC MRI 技术在人类10、11以及动物研究中得到了越来越多的普及, 4、12。在这些研究中, 彭等的结果。4是特别感兴趣的, 因为他们的方法相似, 但当前工作的主要区别是使用0.21 毫米的空间分辨率, 与上述报告中的0.31 毫米相比。有限的空间分辨率大大减少了扫描时间, 但由此产生的局部体积效应可能会影响流量量化, 特别是对较小的船舶6,7。由于测量精度在优先级列表中, 因此在未来的动物研究中建议用更长的扫描时间进行0.21 毫米的空间分辨率。
非门控的 PC MRI 作为血液流量测量的替代方法, 在许多人的研究, 由于其扫描时间大大低于6,13,14,15。然而, 在用于临床前试验的动物中, 不建议使用非门控的 PC MRI, 因为大鼠的心率可以高达 400 bpm, 导致收缩期和舒张阶段之间的快速交替。非门控的 PC-MRI 可能错过关键信息在收缩期, 导致相对较低的流量值和更高的变化7;因此, 它只能用于到达在粗略估计的动物用于前临床试验。
许多扫描参数都与精确的 quantifications 有关, 而 VENC 是其中之一。VENC 低估导致了相位混淆16 , 但较高的 VENC 值将导致图像质量下降17。我们使用的 VENC 值为120厘米/秒, 适合正常成年 SD 大鼠。当预期的血管色调变化, 如不同的物种4, 应优化 VENC 值, 使更好的图像或评估可以获得。
应特别注意议定书的重要步骤, 以取得可靠的结果。首先, 为了避免谐振电路和 MRI 谐振频率的心电图信号的损坏, 建议将心电电缆拧在一起。第二, 大多数小动物 MRI 扫描仪结合循环温水回路, 以保持动物的体温, 而在磁铁。然而, 流动的水引入噪声, 因此, 干扰心电图信号。因此, 在这个封闭的 PC MRI 研究中, 我们建议使用温暖的空气加热系统或纱布垫, 而不是使用温水循环系统, 以提高浇口质量。
应该指出的是, 在这项工作中, 只有2D 的 PC-MRI 序列被用于数据采集。由于扫描时间缩短, 在标准扫描仪中易于实现, 电影门控 2D PC MRI 的基本技术已成为一种很有前途的血流量化工具。然而, 由于缺乏容量采集和可靠的流线跟踪, 因此缺少一些重要信息, 如湍流流动, 2D PC MRI 技术获得的数据是有限的。有时间分辨的 3D pc-mri 脉冲序列, 具有更先进的技术, 如加速电影 PC mri 与压缩传感和并行成像18,19应该在未来的大鼠评价实验中实施。这一改进将有助于提供对速度分布和流动结构的空间方面的洞察力。然而, 本报告中提出的动物制剂和监测协议仍然适用于这些4D 的 PC MRI 技术。
最后, 我们展示了一种简单而可靠的程序, 通过非侵入性的 PC MRI 测量大鼠的血流量。这种成像方法的进一步应用包括药理作用的测试, 病理生理学评估和脑血流动力学评价。

磁共振成像 (MRI) 是一种多功能的方法, 提供了有关内部身体结构和生理学的详细信息, 并越来越多地用于临床诊断和前期动物研究。动物模型是至关重要的, 以更好地了解相当多的临床意义1。由于动物模型在麻醉要求和生理参数方面与人类有很大的不同, 因此对这种动物的 MRI 程序进行优化具有重要意义。
磁共振成像 (mri) 是一种特殊类型的 mri, 利用流动旋转的速度来量化与流动相关的参数, 如血流。借助于 PC MRI, 利用动物模型对主要动脉中的流型进行映射可以帮助揭示心血管病理2。此外, PC MRI 可无创监测病理生理学情况下血液流动的内在变动3。这些观察表明, PC MRI 是一种有价值的方法, 可用于人类心血管疾病的动物模型。
在本报告中, 我们描述了一种定量的血流量在颈总动脉 (共同评估) 的大鼠。两种共同国家评估为头颈部提供含氧血, 颈动脉疾病是中风的主要原因。因此, 检测早期病理在共同国家评估中是至关重要的。这一过程的持续时间约为15分钟, 并可能适用于条件与血流动力学改变, 如动脉粥样硬化或中风。

<table><tbody><tr><td>7T small animal MRI system</td><td>Bruker</td><td></td><td></td></tr><tr><td>Isoflurane&amp;nbsp;</td><td>Baxter</td><td>1001936040</td><td>anesthetic</td></tr><tr><td>ECG lead&amp;nbsp;</td><td>3M</td><td>2269T</td><td></td></tr><tr><td>Matlab</td><td>MathWorks</td><td></td><td>sofeware for image processing</td></tr><tr><td>Monitoring and gating system</td><td>SA instruments, Inc</td><td>Model 1030</td><td></td></tr></tbody></table>

phase contrast magnetic resonance imaging in the rat common carotid artery

相衬磁共振成像 (PC MRI) 是一种无创的方法, 可以量化流量相关参数, 如血流。以前的研究表明, 异常的血流可能与系统性血管危险有关。因此, PC MRI 可以促进从心血管疾病动物模型获得的数据的翻译到相关的临床调查。在本报告中, 我们描述了用电影门控电脑 MRI 测量大鼠颈总动脉血流量的方法, 并讨论了相关的分析方法。这一程序可以在活体, 麻醉动物, 不需要安乐死后的程序。所提出的扫描参数产生可重复测量的血液流量, 表明了优良的重现性的结果。本文所描述的 PC MRI 程序可用于药理试验、病理生理学评估和脑血流动力学评价。

正确的切片几何是确保 PC MRI 实验成功的关键。准确的图像平面定位产生一个 "圆形" 的动脉形状 (图 3a), 随着角度的增加,即, 当它与动脉垂直较少时, 产生的动脉几何变成卵球形, 导致较大的部分体积效果 (图 3b)。严重的局部体积效应会导致对血流的高估6,7。因此, 如果动脉形状为卵球形, 我们主张重新定位图像平面。
图 4显示了一个人心脏周期内血液流动时间变化的内扫描重现性。可见, 血流在收缩期达到最大值, 并在两节舒张期恢复基线。图 5a和5b显示了一个平淡的奥特曼情节和散布情节, 分别在两个血液测量之间的同一会话, 表明了良好的相关性测量 (R2= 0.7, P < 0.001)。通过所提出的扫描参数, 血液流量达到可重复测量, 显示了良好的重现性的结果。这一特点可以证明是有益的测试药理作用的主要动脉8,9。
由于 PC MRI 是一种无创的测量血液流量的方法, 它在需要纵向监测的协议中具有优越性。图 6显示了在2和4月内扫描的动物中一个心脏周期的时间路线, 表明共同国家评估中的血液流动明显依赖年龄, 提示大鼠的快速发育。这些对血液流量的定量评估对于更好地了解循环系统是必不可少的, 因此可以成为中风和动脉粥样硬化的前期研究的潜在有用工具。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57304/57304fig1v2.jpg"> 图 1: 动物监测.(a) 心电图电极放置在右前爪和左后爪上, 呼吸枕传感器放置在动物的躯干下。(b) 心电图和呼吸信号在显示器上明显可见。<a href="/files/ftp_upload/57304/57304fig1v2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57304/57304fig2v2.jpg"> 图 2: 说明 PC MRI 扫描和代表性图像的位置.(a) 从飞行时血管造影的角度对重建的矢状和冠状位置进行切片定位。蓝线表示在共同国家评估的中点水平上的图像平面。(b) 从有代表性的动物拍摄的电影系列图像的一个时间帧的震级和相位图像。红色箭头表示共同评估位置。<a href="/files/ftp_upload/57304/57304fig2v2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57304/57304fig3v2.jpg"> 图 3: 代表级图像.(a) 成像平面垂直于动脉, (b) 成像平面非垂直于动脉。如果成像平面与动脉不垂直, 则由圆形到卵球形的动脉形态发生变化。在红色框中放大包含共同国家评估的区域。<a href="/files/ftp_upload/57304/57304fig3v2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57304/57304fig4v2.jpg"> 图 4:有代表性大鼠血流的扫描内检测.<a href="/files/ftp_upload/57304/57304fig4v2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57304/57304fig5v2.jpg"> 图 5:血液流量测量的剖面内重现性。(a) 比较两个部分之间获得的血液流量测量的平淡-奥特曼情节。实线表示两个测量之间的平均差, 而虚线描述95% 置信区间。(b) 两个血流量测量的散布图。<a href="/files/ftp_upload/57304/57304fig5v2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/57304/57304fig6.jpg"> 图 6: 在2月和4月的老动物中进行纵向扫描, 显示共同国家评估中血液流动的年龄依赖性变化.

Watch this Scientific Journal Video about Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery at JoVE.com

Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery

本程序的总体目标是采用无创相磁共振成像技术对大鼠颈总动脉血流进行测量。

大鼠颈总动脉的相位对比磁共振成像

Phase contrast magnetic resonance imaging (PC-MRI) is a noninvasive approach that can quantify flow-related parameters such as blood flow. Previous ...

phase-contrast-magnetic-resonance-imaging-rat-common-carotid

Nanyang Technological University

Research

JoVE Journal

Medicine

9.4K 次观看.  Chang Gung Memorial Hospital. 本程序的总体目标是采用无创相磁共振成像技术对大鼠颈总动脉血流进行测量。

视频: Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery

Focal Cerebral Ischemia Model by Endovascular Suture Occlusion of the Middle Cerebral Artery in the Rat

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable clinical state; in the development of animal models of focal ischemia, however, achieving reproducibility of experimentally induced infarct volume is essential. The rat is a widely used animal model for stroke due to its relatively low animal husbandry costs and to the similarity of its cranial circulation to that of humans2,3. In humans, the middle cerebral artery (MCA) is most commonly affected in stroke syndromes and multiple methods of MCA occlusion (MCAO) have been described to mimic this clinical syndrome in animal models. Because recanalization commonly occurs following an acute stroke in the human, reperfusion after a period of occlusion has been included in many of these models. In this video, we demonstrate the transient endovascular suture MCAO model in the spontaneously hypertensive rat (SHR). A filament with a silicon tip coating is placed intraluminally at the MCA origin for 60 minutes, followed by reperfusion. Note that the optimal occlusion period may vary in other rat strains, such as Wistar or Sprague-Dawley. Several behavioral indicators of stroke in the rat are shown. Focal ischemia is confirmed using T2-weighted magnetic resonance images and by staining brain sections with 2,3,5-triphenyltetrazolium chloride (TTC) 24 hours after MCAO.

Surgical induction of ischemic brain damage in the rat is a widely used model for stroke research. Here we demonstrate the induction of focal cerebral ischemia by occlusion of the middle cerebral artery. Visualization of the resulting infarct by histological staining and magnetic resonance imaging is also shown.

焦距脑缺血模型大鼠大脑中动脉的血管内缝合闭塞

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable ...

科研

神经科学

Optimized System for Cerebral Perfusion Monitoring in the Rat Stroke Model of Intraluminal Middle Cerebral Artery Occlusion

The translational potential of pre-clinical stroke research depends on the accuracy of experimental modeling. Cerebral perfusion monitoring in animal models of acute ischemic stroke allows to confirm successful arterial occlusion and exclude subarachnoid hemorrhage. Cerebral perfusion monitoring can also be used to study intracranial collateral circulation, which is emerging as a powerful determinant of stroke outcome and a possible therapeutic target. Despite a recognized role of Laser Doppler perfusion monitoring as part of the current guidelines for experimental cerebral ischemia, a number of technical difficulties exist that limit its widespread use. One of the major issues is obtaining a secure and prolonged attachment of a deep-penetration Laser Doppler probe to the animal skull. In this video, we show our optimized system for cerebral perfusion monitoring during transient middle cerebral artery occlusion by intraluminal filament in the rat. We developed in-house a simple method to obtain a custom made holder for twin-fibre (deep-penetration) Laser Doppler probes, which allow multi-site monitoring if needed. A continuous and prolonged monitoring of cerebral perfusion could easily be obtained over the intact skull.

Cerebral perfusion monitoring has been demonstrated to improve accuracy in ischemic stroke models. Technical difficulties often limit the use of this essential tool for cerebrovascular research. In this video, an optimized system is shown to obtain a single or multi-site hemodynamic monitoring during intraluminal middle cerebral artery occlusion in rats.

优化系统的脑灌注监测在中风模型大鼠的大脑中动脉闭塞腔内

The translational potential of pre-clinical stroke research depends on the accuracy of experimental modeling. Cerebral perfusion monitoring in animal ...

医学

Diffusion Imaging in the Rat Cervical Spinal Cord

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a diagnostic and prognostic tool in cases of disease or injury. Diffusion weighted imaging (DWI), is sensitive to the thermal motion of water molecules and allows for inferences of tissue microstructure. This report describes a protocol to acquire and analyze DWI of the rat cervical spinal cord on a small-bore animal system. It demonstrates an imaging setup for the live anesthetized animal and recommends a DWI acquisition protocol for high-quality imaging, which includes stabilization of the cord and control of respiratory motion. Measurements with diffusion weighting along different directions and magnitudes (b-values) are used. Finally, several mathematical models of the resulting signal are used to derive maps of the diffusion processes within the spinal cord tissue that provide insight into the normal cord and can be used to monitor injury or disease processes noninvasively.

The goal of this protocol is to obtain high-quality diffusion weighted magnetic resonance imaging (DWI) of the rat spinal cord for noninvasive characterization of tissue microstructure. This protocol describes optimizations of the MRI sequence, radiofrequency coil, and analysis methods to enable DWI images free from artifacts.

在大鼠颈脊髓弥散成像

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a ...

Simultaneous PET/MRI Imaging During Mouse Cerebral Hypoxia-ischemia

Dynamic changes in tissue water diffusion and glucose metabolism occur during and after hypoxia in cerebral hypoxia-ischemia reflecting a bioenergetics disturbance in affected cells. Diffusion weighted magnetic resonance imaging (MRI) identifies regions that are damaged, potentially irreversibly, by hypoxia-ischemia. Alterations in glucose utilization in the affected tissue may be detectable by positron emission tomography (PET) imaging of 2-deoxy-2-(18F)fluoro-&#7429;-glucose ([18F]FDG) uptake. Due to the rapid and variable nature of injury in this animal model, acquisition of both modes of data must be performed simultaneously in order to meaningfully correlate PET and MRI data. In addition, inter-animal variability in the hypoxic-ischemic injury due to vascular differences limits the ability to analyze multi-modal data and observe changes to a group-wise approach if data is not acquired simultaneously in individual subjects. The method presented here allows one to acquire both diffusion-weighted MRI and [18F]FDG uptake data in the same animal before, during, and after the hypoxic challenge in order to interrogate immediate physiological changes.

The method presented here uses simultaneous positron emission tomography and magnetic resonance imaging. In the cerebral hypoxia-ischemia model, dynamic changes in diffusion and glucose metabolism occur during and after injury. The evolving and irreproducible damage in this model necessitates simultaneous acquisition if meaningful multi-modal imaging data are to be acquired.

同时PET / MRI成像在小鼠脑缺氧缺血

Dynamic changes in tissue water diffusion and glucose metabolism occur during and after hypoxia in cerebral hypoxia-ischemia reflecting a bioenergetics ...

A Magnetic Resonance Imaging Protocol for Stroke Onset Time Estimation in Permanent Cerebral Ischemia

MRI provides a sensitive and specific imaging tool to detect acute ischemic stroke by means of a reduced diffusion coefficient of brain water. In a rat model of ischemic stroke, differences in quantitative T1 and T2 MRI relaxation times (qT1 and qT2) between the ischemic lesion (delineated by low diffusion) and the contralateral non-ischemic hemisphere increase with time from stroke onset. The time dependency of MRI relaxation time differences is heuristically described by a linear function and thus provides a simple estimate of stroke onset time. Additionally, the volumes of abnormal qT1 and qT2 within the ischemic lesion increase linearly with time providing a complementary method for stroke timing. A (semi)automated computer routine based on the quantified diffusion coefficient is presented to delineate acute ischemic stroke tissue in rat ischemia. This routine also determines hemispheric differences in qT1 and qT2 relaxation times and the location and volume of abnormal qT1 and qT2 voxels within the lesion. Uncertainties associated with onset time estimates of qT1 and qT2 MRI data vary from &plusmn; 25 min to &plusmn; 47 min for the first 5 hours of stroke. The most accurate onset time estimates can be obtained by quantifying the volume of overlapping abnormal qT1 and qT2 lesion volumes, termed 'Voverlap' (&plusmn; 25 min) or by quantifying hemispheric differences in qT2 relaxation times only (&plusmn; 28 min). Overall, qT2 derived parameters outperform those from qT1. The current MRI protocol is tested in the hyperacute phase of a permanent focal ischemia model, which may not be applicable to transient focal brain ischemia.

A protocol for stroke onset time estimation in a rat model of stroke exploiting quantitative magnetic resonance imaging (qMRI) parameters is described. The procedure exploits diffusion MRI for delineation of the acute stroke lesion and quantitative T1 and T2 (qT1 and qT2) relaxation times for timing of stroke.

脑缺血中风发作时间估计的磁共振成像协议

MRI provides a sensitive and specific imaging tool to detect acute ischemic stroke by means of a reduced diffusion coefficient of brain water. In a rat ...

Quantitative MRI of Endothelial Permeability and (Dys)function in Atherosclerosis

Cardiovascular diseases are the leading causes of death worldwide. A permeable/leaky and dysfunctional endothelium is considered the earliest marker of vascular damage and thought to drive atherosclerosis. A method to identify these changes in vivo would be desirable in the clinic. Magnetic resonance imaging (MRI)-based tools and other technologies have enabled a profound understanding of the role of the endothelium in cardiovascular diseases and risk in vivo. There is, however, a need for reproducible and simple approaches for extracting quantifiable data reflective of endothelial damage from a single imaging study. A non-invasive, easy-to-implement, and quantitative MRI workflow was developed to acquire and analyze images that allow the quantification of two imaging biomarkers of arterial endothelial damage (leakiness/permeability and dysfunction). Here, the protocol describes the application of this method in the brachiocephalic artery of atherosclerotic ApoE-/- mice using a clinical MRI scanner. First, late gadolinium enhancement (LGE) and Modified Look-Locker Inversion Recovery (MOLLI) T1 mapping protocols to quantify endothelial leakage using an albumin-binding probe are described. Second, anatomic, and quantitative blood flow sequences to measure endothelial dysfunction, in response to acetylcholine are described. Importantly, the method outlined here allows the acquisition of high-spatial-resolution 3D images with large volumetric coverage enabling accurate segmentation of vessel wall structures to improve inter- and intra-observer variability and to increase reliability and reproducibility. Additionally, it provides quantitative data without the need for high-temporal resolution for complex kinetic modeling, making it model-independent and even allowing for imaging of highly mobile vessels (coronary arteries). Therefore, the approach simplifies and expedites data analysis. Finally, this method can be implemented on different scanners, can be extended to image different arterial beds, and is clinically applicable for use in humans. This method could be used to diagnose and treat patients with atherosclerosis by adopting a precision-medicine approach.

Quantitative MRI of Endothelial Permeability and Dysfunction in Atherosclerosis

We have developed an accurate, non-invasive, and easy-to-use method to quantify endothelial permeability and dysfunction in the arteries using Magnetic Resonance Imaging (MRI), named qMETRIC. This technique enables assessing vascular damage and cardiovascular risk associated with atherosclerosis in preclinical models and humans.

Cardiovascular diseases are the leading causes of death worldwide. A permeable/leaky and dysfunctional endothelium is considered the earliest marker of ...

生物工程

Ferric Chloride-induced Canine Carotid Artery Thrombosis: A Large Animal Model of Vascular Injury

Occlusive arterial thrombosis leading to cerebral ischemic stroke and myocardial infarction contributes to ~13 million deaths every year globally. Here, we have translated a vascular injury model from a small animal into a large animal (canine), with slight modifications that can be used for pre-clinical screening of prophylactic and thrombolytic agents. In addition to the surgical methods, the modified protocol describes the step-by-step methods to assess carotid artery canalization by angiography, detailed instructions to process both the brain and carotid artery for histological analysis to verify carotid canalization and cerebral hemorrhage, and specific parameters to complete an assessment of downstream thromboembolic events by utilizing magnetic resonance imaging (MRI). In addition, specific procedural changes from the previously well-established small animal model necessary to translate into a large animal (canine) vascular injury are discussed.

Here, we present the modifications necessary to a well characterized and commonly used small animal ferric chloride-induced (FeCl3) carotid artery injury model for use in a large animal vascular injury model. The resulting model can be utilized for pre-clinical trial assessment of both prophylactic and thrombolytic pharmacological and mechanical interventions.

氯化铁诱导的犬颈动脉血栓形成: 一种大的血管损伤动物模型

Occlusive arterial thrombosis leading to cerebral ischemic stroke and myocardial infarction contributes to ~13 million deaths every year globally. Here, ...

Middle Cerebral Artery Occlusion Allowing Reperfusion via Common Carotid Artery Repair in Mice

The ischemic stroke is a major cause of adult long-term disability and death worldwide. The current treatments available are limited, with only tissue plasminogen activator (tPA) as an approved drug treatment to target ischemic strokes. Current research in the field of ischemic stroke focuses on better understanding the pathophysiology of stroke, to develop and investigate novel pharmaceutical targets. Reliable experimental stroke models are crucial for the progression of potential treatments. The middle cerebral artery occlusion (MCAO) model is clinically relevant and the most frequently used surgical model of ischemic stroke in rodents. However, the outcomes of this model, such as lesion volume, are associated with high levels of variability, particularly in mice. The alternative MCAO model described here allows the reperfusion of the common carotid artery (CCA) and the increased perfusion of the middle cerebral artery (MCA) territory, using a tissue pad with fibrinogen-based sealant to repair the vessel, and the improved welfare of the mice by avoiding external carotid artery (ECA) ligation. This reduces the reliance on the Circle of Willis, which is known to be highly anatomically variable in mice. Representative data show that using this alternative surgical approach decreases the variability in lesion volumes between the traditional MCAO approach and the alternative approach described here.

Intraluminal filament occlusion of the middle cerebral artery is the most frequently used in vivo model of experimental stroke in rodents. An alternative surgical approach to allow common carotid artery repair is performed here, which allows the reperfusion of the common carotid artery and a full reperfusion to the middle cerebral artery territory.

颅内动脉闭塞允许经普通颈动脉修复再灌注的研究

The ischemic stroke is a major cause of adult long-term disability and death worldwide. The current treatments available are limited, with only tissue ...

Cardiac Magnetic Resonance Imaging

Source: Frederick W. Damen and <a href="https://www-jove-com.remotexs.ntu.edu.sg/author/Craig+J._Goergen">Craig J. Goergen</a>, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
In this video, high field, small-bore magnetic resonance imaging (MRI) with physiological monitoring is demonstrated to acquire gated cine loops of the murine cardiovascular system. This procedure provides a basis for assessing left-ventricular function, visualizing vascular networks, and quantifying motion of organs due to respiration. Comparable small animal cardiovascular imaging modalities include high-frequency ultrasound and micro-computed tomography (CT); however, each modality is associated with trade-offs that should be considered. While ultrasound does provide high spatial and temporal resolution, imaging artifacts are common. For example, dense tissue (i.e., the sternum and ribs) can limit imaging penetration depth, and hyperechoic signal at the interface between gas and liquid (i.e., pleura surrounding the lungs) can blur contrast in nearby tissue. Micro-CT in contrast does not suffer from as many in-plane artifacts, but does have lower temporal resolution and limited soft-tissue contrast. Furthermore, micro-CT uses X-ray radiation and often requires the use of contrast agents to visualize vasculature, both of which are known to cause side effects at high doses including radiation damage&#160; and renal injury. Cardiovascular MRI provides a nice compromise between these techniques by negating the need for ionizing radiation and providing the user with the ability to image without contrast agents (although contrast agents are often used for MRI).
This data was acquired with a triggering Fast Low Angle SHot (FLASH) MRI sequence that was gated off of the R-peaks in the cardiac cycle and expiratory plateaus in respiration. These physiological events were monitored through subcutaneous electrodes and a pressure-sensitive pillow that was secured against the abdomen. To ensure the mouse was properly warmed, a rectal temperature probe was inserted and used to control the output of a MRI-safe heating fan. Once the animal was inserted into the bore of the MRI scanner and navigation sequences were run to confirm positioning, the gated FLASH imaging planes were prescribed and data acquired. Overall, high field MRI is a powerful research tool that can provide soft tissue contrast for the study of small animal disease models.

Cardiac MRI: Principle and Imaging

心脏磁共振成像

Source: Frederick W. Damen and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
In this video, high ...

教育

JoVE Science Education

工程学

生物医学工程

 Phase Contrast Magnetic Resonance Imaging to Assess Blood Flow in the Arteries of a Rat

<a href='https://app-jove-com.remotexs.ntu.edu.sg/v/57304/phase-contrast-magnetic-resonance-imaging-rat-common-carotid'>Source: Chiu, S., et al. Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery. J. Vis. Exp. (2018).</a>This video demonstrates phase contrast magnetic resonance imaging (PC-MRI) to measure blood flow in the common carotid artery of a rat. After securing an anesthetized rat on the MRI bed and ensuring stable physiological parameters, the common carotid artery is scanned to capture images at defined intervals. Blood flow is then computed from these images to evaluate changes throughout the cardiac cycle.

Source: Chiu, S., et al. Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery. J. Vis. Exp. (2018).This video demonstrates phase ...