In vivo H-1 magnetic resonance imaging and spectroscopy of the rat spinal cord using an inductively-coupled chronically implanted RF coil

An inductively coupled, chronically implanted short-solenoid coil was used to obtain in vivo localized H-1 NMR spectra and diffusion-weighted images f rom a rat spinal cord. A 5 x 8 mm two-turn elliptically shaped solenoid coi l was implanted in rats at the site of a T-12 vertebral-level laminectomy. Excitation was achieved solely by a 3 x 3 cm external surface coil, and sig nal detection was achieved by inductively coupling the external coil to the implanted coil. The image signal-to-noise ratio (SNR) obtained with the in ductively-coupled implanted coil was compared with that obtained using a li near or a quadrature external surface coil. The implanted coil provided a g ain by over a factor of 3 in SNR. The implanted coil was used to measure lo calized 1H spectra in vivo at the T13/L1 spinal-cord level within a 1.85 x 1.85 x 4.82 mm (16.5 muL) volume. With 256 averages, a similar to3-s repeti tion delay and respiratory gating, a high-quality spectrum was acquired in 13 min. In addition, water translational diffusion was measured in three or thogonal directions using a stimulated-echo imaging sequence, with a short echo time (TE), to produce a quantitative map of diffusion in a rat spinal cord in vivo. (C) 2001 Wiley-Liss, Inc.