FUNCTIONAL IMAGING OF BRAIN

本项目的目标是开发MRI技术， 监测大脑功能。 这项工作是通过开发一个 灌注MRI技术依赖于动脉自旋标记， 内源性水作为灌注示踪剂。 在过去的五年里， 这类灌注MRI技术已经被确立为有用的 用于测量休息时大脑中的局部血流量， 激活，以及在人类和动物模型中的疾病状态。 这项技术可以定量测量局部血流 随着MRI的空间和时间分辨率在各种 组织中 这类技术的进一步发展正在进行中。 进行了旨在扩展策略的实验， 动脉自旋标记，利用标记的水作为探针， 水提取到组织中，并使其成为常规，以获得快速 小鼠大脑中的三维图像。 此外，当 应用于大脑，这类灌注成像技术应该 对大脑绘图研究有用，特别是， BOLD技术的补充。 目前，所有功能性MRI 技术监测神经元激活的血液动力学后果 而不是神经元活动的直接影响。 的级联 导致神经元激活的事件是 神经递质，去极化，钙内流，释放 神经递质等。血液动力学变化作为一种反应发生， 来维持体内平衡 更直接的MRI测量 神经元激活可能非常有用。 初步结果 提示Mn ~（2+）可能是一种优良造影剂 在动物模型中与神经元活动相关的钙内流。 在 此外，Mn 2 ~-似乎一旦被激活就充当顺行神经元示踪剂。 进入神经元。 这两个令人兴奋的结果打开了 扩展脑功能MR技术的可能性。

The objectives of this project are to develop MRI techniques for monitoring of brain function. This work was begun by development of a perfusion MRI technique that relies on arterial spin labeling of endogenous water as a perfusion tracer. Over the past five years, this class of perfusion MRI technique has been established as useful for measuring regional blood flow in the brain during rest, task activation, and in disease states in both humans and animal models. This technique makes quantitative measurements of regional blood flow with the spatial and temporal resolution of MRI in a variety of tissues. Further development of this class of techniques is being carried out with experiments designed to extend strategies for arterial spin labeling, make use of the labeled water as a probe of water extraction into tissue, and make it routine to acquire rapid three dimensional images in the mouse brain. Furthermore, when applied to the brain, this class of perfusion imaging technique should be useful for brain mapping studies and, in particular, forms a complement to BOLD techniques. Presently, all functional MRI techniques monitor the hemodynamic consequences of neuronal activation rather than a direct effect of neuronal activity. The cascade of events that lead to neuronal activation are release of neurotransmitter, depolarization, influx of calcium, release of neurotransmitter, and so on. Hemodynamic changes occur as a response of the brain to maintain homeostasis. A more direct MRI measure of neuronal activation might be very useful. Preliminary results indicate that Mn2~ might be an excellent contrast agent to probe calcium influx associated with neuronal activity in animal models. In addition, Mn2~ appears to act as an anterograde neuronal tracer once it enters neurons. Both of these exciting results open the possibility of extending functional MR techniques for the brain.