FUNCTIONAL IMAGING IN RODENT BRAIN USING INTRAVASCULAR IRON OXIDE CONTRAST

使用血管内氧化铁对比进行啮齿动物大脑功能成像

• 批准号: 6310009
• 负责人: ALEXANDER D CRESPIGNY
• 金额: $ 1.55万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6310009
• 关键词: Mammalia; bioimaging /biomedical imaging; biomedical resource; magnetic resonance imaging; technology /technique

INTRODUCTION: High resolution functional magnetic resonance imaging (fMRI) of the rat cortex provides a valuable technique for investigating plasticity and functional recovery following trauma. fMRI has been used to demonstrate cortical activation in anaesthetized animals by exploiting the BOLD effect and the signal intensity changes typically seen are in the order of a few percent. METHODS: Six male rats were anesthetized with halothane in oxygen for venous and arterial catheterization then switched to a-chloralose for the remainder of the experiment and images were obtained on a 4.7T Varian INOVA system. Gradient echo (GRE) images were acquired every 6 seconds. For comparison high speed T2-weighted spin echo (SE) fMRI was performed using a RARE sequence. To increase the sensitivity to microscopic magnetic susceptibility variations, the first echo time was increased to 56ms. The fMRI activation paradigm consisted of off-on-off sequence with each period lasting 60s. Forepaw stimulation was performed with a train of 3V pulses of 3ms duration at 3Hz, delivered via a pair of small needle electrodes inserted subcutaneously in the left paw. Experiments were performed with both the GRE and RARE sequences before and after injection of Combidex*. RESULTS: A 4-5% increase in signal intensity was seen with the GRE imaging (BOLD effect) during activation. Following injection of Combidex*, there was a dramatic 15-20% decrease in signal intensity during activation reflecting a change in CBV. Using these optimal conditions higher resolution 128x128 pixel GRE images with in plane resolution of greater 250mm could be readily obtained. The signal change measured with the RARE sequence during activation was comparable to that seen with the GRE sequence using the BOLD mechanism. However, after injection of contrast agent 4-5% reduction in activation signal change was detected. CONCLUSIONS: High resolution functional maps of the rat cortex following sensory stimulation can be readily obtained using GRE sequences or fast SE sequences in conjunction with Combidex*. Tailored MR protocols can be made selective for different vascular components of the activation response. This approach is relatively insensitive to macroscopic susceptibility and is thus ideally suited to high fields fMRI experiments in animals.

简介：高分辨率功能磁共振 大鼠皮层的功能磁共振成像（fMRI）提供了一种有价值的技术， 研究创伤后的可塑性和功能恢复。 功能磁共振成像已被用来证明皮层激活麻醉 动物通过利用BOLD效应和信号强度的变化 通常看到的数量级为百分之几。 方法：6名男性 大鼠用氟烷在氧气中麻醉， 动脉导管插入术，然后切换到a-氯醛糖为 实验的剩余部分和图像在4.7T Varian上获得 INOVA系统。 梯度回波（GRE）图像采集每6 秒 为了比较，高速T2加权自旋回波（SE）fMRI 使用RARE序列进行。 为了提高对 微观磁化率变化，第一回波时间 增加到56 ms。 功能磁共振成像激活模式包括 开关时序，每个周期持续60 s。 前爪刺激 用3 Hz下持续时间为3 ms的一系列3V脉冲进行， 通过一对插入的小针电极输送 左爪皮下注射。 实验用两种 注射Combidex* 前后的GRE和RARE序列。 结果：GRE信号强度增加4- 5 激活期间的成像（BOLD效应）。 注射后 Combidex*，信号强度显著降低15-20% 反映CBV的变化。 利用这些最佳 条件更高的分辨率128 x128像素GRE图像， 可以容易地获得大于250 mm的分辨率。 信号 在激活过程中使用RARE序列测量的变化是 与使用BOLD的GRE序列所见的结果相当 机制 然而，注射造影剂后， 检测到激活信号变化。 结论：高 大鼠皮层的分辨功能图 使用GRE序列或快速SE可以容易地获得刺激 序列与Combidex* 结合。 定制的MR协议可以 对激活的不同血管成分进行选择性 反应 这种方法对宏观的相对不敏感 因此非常适合高场fMRI 动物实验。