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

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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