Study on the metabolism underlying brain function using an ultra high field multinuclear MRI

我们在4.7T高场磁系统中利用液晶投影仪、非磁性显示器或LED护目镜实现了视觉引导或刺激装置。在每种情况下，显示器都通过TTL或RF触发与EPI测量同步。利用该视觉显示系统进行了手指敲击或棋盘格视觉刺激的fMRI测量，为了提高人脑局部^1H MRS测量的灵敏度，我们设计并制作了两种多通道RF线圈。一种是使用4个回路元件的半体积线圈，另一种是使用8个微带线元件的全体积线圈。在任一种情况下，与常规TEM型正交RF线圈相比，利用水体模进行自旋激发所需的RF功率小得多，我们还发展了一种脑代谢物的绝对定量方法，该方法以水共振作为内标，对从局部区域（VOI）获得的^1H谱进行去卷积，在人类大脑中。基于组织分割，根据GM、WM和CSF在VOI中的分布估计VOI中的体内水浓度。通过这种方法，我们可以在10分钟内定量9种代谢物，在3 x 3 x 3 cm VOI中，2.7 min内产生7种代谢物。在视觉刺激过程中，我们使用前面描述的方法在位于枕叶的VOI中进行了1H/31 P双核测量。我们发现，有15个主要代谢产物的VOI之间的刺激和休息期间没有变化。这意味着在大脑运作过程中大脑代谢的强大稳态。在给予38 × 152 g乙醇的脑中证实了类似的强稳态。

We implemented visual guiding or stimulating apparatus in the 4.7T high field magnet system utilizing liquid crystal projector, non-magnetic display, or LED goggles. In each case the display is synchronized with EPI measurements via TTL or RF triggering. By using this visual display system we performed fMRI measurements with a paradigm of finger tapping or checkerboard visual stimulation.In order to improve the sensitivity in localized ^1H MRS measurements in human brain we designed and manufactured two kinds of multi-channel RF coils. One is a half volume coil using 4 loop elements, and another is a, full volume coil using 8 microstrip line elements. In either case the required RF power for spin excitation with a water phantom was considerably smaller compared with a conventional TEM type quadrature RF coil, which means an improvement in the signal to noise ratio in the human brain measurement.We also developed an absolute quantification method for brain metabolites using the water resonance as an internal standard in the deconvolution of ^1H spectrum obtained from the localized area (VOI) in human brain. In vivo water concentration in the VOI was estimated from the distribution of GM, WM, and CSF in VOI based on the tissue segmentation. By this method we can quantify nine metabolites in ten min., and seven metabolites in 2.7 min in the 3 x 3 x 3 cm VOI. We conducted 1H/31P dual nuclei measurements in a VOI located in occipital lobe during the visual stimulation using a method described earlier. We found there was no change in 15 major metabolites in the VOI between the stimulation and resting periods. This means a strong homeostasis in the brain metabolism during the brain functioning. The similar strong homeostasis was confirmed in the brain administered with 38〜152g of ethanol.