NMR in vivo multinuclear imaging at 7 T

Since the installation of 7T MRI system (NIRS/KOBELCO/Bruker) in October 2004, we have been working on the in vivo multinuclear imaging and MRS. The magnet was developed by NIRS and JASTEC (KOBELCO), 400 mm bore, self shielded, and zero boil off freezing system for liquid helium. This report is on the multinuclear applications to the pharmaco-dynamical study of fluorine containing drug 5-FU with 19F, and 17O imaging towards oxygen consumption study in mice. In order to obtain images from low concentration or low sensitivity nuclear spins, fast sequences are compared for 19F at 282 MHz, and for 17O at 40 MHz. Fast spin echo was better than true-FISP for 19F in giving stable image intensity for all the metabolites in various organs. FSE is also capable of giving the full time course of drug dynamics by simultaneous multi-spectral line selection: the distribution of effective anabolites especially at the tumor, the formation of catabolites in and excretion from the liver as well as the fate of administrated drug. The method is benefited by the wide chemical shift separation and high sensitivity of high field MR. For 17O, true-FISP was the best among FISP, FS E and Flash. Unlike the case of 19F, the smaller effect of magnetic susceptibility at he resonance frequency of 40 MHz enabled us to use FISP for whole body MRI of 17O. (author)