Development of Magnetic Resonance Imaging of Neuronal activity and its application to functional brain imaging

我们尝试利用核磁共振成像（MRI）技术发展神经元活动的地形成像，以应用于新的脑功能制图。其基本思路是通过微成像和超快速扩散磁共振成像相结合，检测神经元电活动过程中神经元细胞膜间的水扩散。研究项目由三部分组成。首先是发展了利用核磁共振成像技术对神经元活动进行成像的技术。第二个是将这项技术应用于实验动物的研究，并检验它是否可以应用于大脑功能绘图。第三是将该技术应用于临床1.5T MRI扫描仪，并研究人类应用的可能性。在最初的两年里，研究的重点是开发实验核磁共振成型机的硬件（7.0 Unity INOVA300SWB, Varian， USA）。由于预算的削减，我们无法获得超强的梯度…更多的线圈（20高斯/厘米）。我们采用传统的梯度线圈（2Gaus/cm）和新引进的成像阵列处理器开发了微成像系统。在此基础上，我们尝试制作了新推出的微成像阵列处理器。在本研究之外，我们尝试在临床MRI扫描仪磁体中工作的小型实验MRI系统（Mrmics, Jyonan-Denshi, Tukuba）上进行微成像。我们开发的脉冲序列是基于回波平面成像（EPI）。90度脉冲后，180度制备脉冲前后分别施加扩散探测梯度，检测水在神经元细胞膜上扩散对信号的影响。利用常规梯度法可以获得矩阵尺寸为10微米的超快速扩散加权微像。但到目前为止，我们还无法在实验动物身上获得这种扩散显微图像。原因可能是梯度强度不足以得到更小的基体和更强的扩散梯度功率。因此，我们最初要求的超强梯度是进行这种实验所必需的。同样对于临床扫描仪的应用，它需要更强的梯度和更强的磁场，如3.0T或4.0T。最后，我们想强调的是，如果我们有更强大的扫描仪，将有可能通过MRI获得神经元活动图像。少

We tried to develop the topographic imaging of neuronal activity by using magnetic resonance imaging (MRI) techniques for applying to new functional brain mapping. The basic idea is to detect the water diffusion associated between the neuronal cell membrane during the neuronal electrical activity by the combination with microimaging and ultra-fast diffusion MR imaging. The research projects consisted of three parts. The first was to develop the technique of imaging of neuronal activity by using MRI method. The second was to apply this technique to study the experimental animals and to examine if this can be applied to the brain functional mapping. The third was to apply this technique to the clinical 1.5T MRI sacnner and to examine the possibility of human application. During initial two years, the study was focused on developing the hardware of experimental MRI machine (7.0 Unity INOVA300SWB, Varian, USA). Due to the cut of the budget, we could not get the ultra-super strong gradient … More coil (20Gause/cm). We developed the microimaging system using the conventional gradient coil (2Gaus/cm) and the imaging array processor which was newly intoduced. In addition to this study, we tried to make the microimaging array processor which was newly intoduced. In addition to this study, we tried to make the microimaging on the small experimental MRI system (Mrmics, Jyonan-Denshi, Tukuba) which works in the magnet of clinical MRI scanner. The pulse sequence we developed is based on the Echo Planar Imaging (EPI). Following the 90 degree pulse, diffusion probing gradients were applied before and after 180 degree preparation pulse and signal which affected by the diffusion of water across the neuronal cell membrane was detected. We could obtain the ultra-fast diffusion weighted microimage with matrices size of 10 mirometer each by using the conventional gradient. But so far, we could not get this kind of diffusion microimage on the experimental animal. The reason would be that the gradient strength is not enough to get more small matrix and more strong diffusion gradient power. Therefore, the ultra-super strong gradient which we initially required is essential to perform this kind of experiment. Also for the application to the clinical scanner, it requires the more strong gradient and more strong magnetic field such as 3.0T or 4.0T. Finally, we would like to stress that it will be possible to obtain the neuronal activity image by using MRI if we can get more powerful scanner. Less