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

点击翻译按钮获取中文摘要

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.