Development of spectroscopic diffusion weighted imaging of metabolites in the brain

我们利用磁共振(MR)方法建立了脑组织中各种代谢物的扩散加权成像(DWI)，可以用来研究脑组织代谢中底物的动态性质。这将被称为光谱DWI(SP-DWI)，因为这是水DWI和磁共振波谱(MRS)两种技术的结合。作为第一步，我们开发了用于SP-DWI的磁流变硬件。硬件中最重要的因素是对强磁场和无涡流问题的强梯度线圈的要求。对于我们实验室的4.7特斯拉系统(CSI-II)，对于SP-DWI，观测到的信号不够强，而对于加州大学旧金山分校的7.0特斯拉系统，SP-DWI则获得了较强的信号强度。8606TECROW梯度线圈功放为…提供优质电源更强大的力量。然而，由于我们提供的资助金被削减了，我们遇到了必须自己制作梯度线圈的麻烦，我们可以消除涡流问题。为了解决这一问题，引入无涡流的屏蔽梯度线圈势在必行，在这种情况下，我们设计了脉冲序列的研制，用于实验研究。我们集中在^1H核上，而不是水质子。我们将DWI所必需的运动探测梯度(MPG)脉冲引入到由双自旋回波方法获得的定域MRS脉冲序列中。在以乳酸和N-乙酰丙氨酸为标准溶液的实验中，在4.7特斯拉系统上，可以从200-300 mm的高浓度溶液中获得SP-DWI。在用大鼠进行的实验中，实际无法获得足够的信号。从这些实验中可以看出，SP-DWI对于研究代谢产物在组织中的分子扩散将是非常独特和有用的。继续发展这些重要方法是必不可少的。虽然希望使用超高场MR设备，但未来可能使用4.7特斯拉系统来获得数据。该方法将成为研究脑功能和新陈代谢的重要方法之一。较少

We have designed to develop the diffusion weighted imaging (DWI) of various metabolites in the brain tissue using magnetic resonance (MR) method, by which dynamic property of substrates in metabolism of brain tissue could be investigated. This will be called spectroscopic DWI (SP-DWI) because of the combination of two techniques of water DWI and the Magnetic Resonance spectroscopy (MRS). As the first step, we have developed the MR hardware for SP-DWI.The most important factors in the hardware are the requirement of strong magnetic field and the strong gradient coil without eddy current problems. With the 4.7 Tesla system (CSI-II) in our laboratory, the observed signal is not strong enough for SP-DWI, while with the 7.0 Tesla system in the University of California San Francisco, the strong signal intensity was obtained for SP-DWI.The strong gradient with eddy current free is the other indispensable bevice. The amplifier for gradient coil (8606 TECROW) has good quality for supplying enou … More gh power. However, we had the trouble that we must made the gradient coil by ourselves because of the cut of our offered grant, and we could eliminate the the problem of eddy current. In order to resolve this problem, it is indispensable to introduce the shielded gradient coil which have no eddy current.Under those circumstances, we had designed the development of pulse sequence for the the experimental study. We concentrated on ^1H nuclei other than water proton. We have introduced the motion probing gradient (MPG) pulse necessary for DWI to the pulse sequence of localized MRS obtained by double spin echo method. In the experiment using standard solution of lactate and N-acetylalanine, the SP-DWI could be obtained from the solution of high concentration with 200-300 mM on the 4.7 Tesla system. In the experiment using rats, enough signal could not be obtained practically. It is still necessary to improve the sequence and the optimization of those technique.From those experiment, it becomes clear that SP-DWI would be extremely unique and useful for the investigation of molecular diffusion of metabolites in tissues. It is indispensable to continue to develop these important method. Although it is desirable to use ultra-high field MR device, it may be possible to obtain data using a 4.7 Tesla system in future. This method will be one of the most important methods to investigate the brain function and metabolism. Less