Study for ultra-fast and highly-sensitive MR spectroscopic imaging using a high-field magnet and a high-performance gradient coil.

在一台7T高场MR扫描仪上安装高性能梯度系统，最大梯度强度为100 G/cm，内径为60 mm。为了利用异核多量子相干（HMQC）技术实现高灵敏度的1H-探测小鼠脑13C光谱成像，介绍了一种由直径60 mm的体积线圈（Tx）、直径15 mm的表面线圈（Rx）和T/R控制器组成的1H射频线圈系统，并将国产13C表面线圈组合在一起。制备了利用高速回波平面成像技术的EPSI脉冲程序，但由于小鼠脑体积小，且7T的高磁场强度使谱带宽度较宽，未能获得预期的时间分辨率提高。在HMQC化学位移成像（CSI）中，跳过8 x 8 = 64个相位编码步骤的k空间4个角的数据采集，大约可以获得相似的空间分辨率数据。2/3采集时间。利用这些技术，在20分钟的时间分辨率下，成功地观察了小鼠脑内13c -谷氨酸和13c -葡萄糖产生的谷氨酰胺代谢物图像的序列变化。

A high-performance gradient system, with maximal gradient strength of 100 G/cm and inner diameter of 60 mm, was installed to a 7T high-field MR scanner. To realize highly-sensitive 1H-detected 13C spectroscopic imaging of mouse brain using hetero-nuclear multiple-quantum coherence (HMQC), a 1H RF coil system, consisting of a volume coil of 60 mm in diameter for transmission (Tx), a surface coil of 15 mm in diameter for receiving (Rx) and T/R controller, was introduced and a home-built 13C surface coil was combined. A pulse program of EPSI, which utilizes a high-speed echo planar imaging technique, was prepared, but expected increase in time-resolution was not obtained because of the small-sized mouse brain and the wide spectral band width due to the high magnetic field strength of 7T. In chemical shift imaging (CSI) with HMQC, the data acquisitions at 4 corners of k-space with8 x 8 = 64 phase encoding steps were skipped and similar spatial resolution data could be obtained in an approx. 2/3 acquisition time. Using these techniques, sequential changes in metabolite images of 13C-glutamate and glutamine generated from infused 13C-glucose were successfully observed in mouse brain with a time resolution of 20 minutes.