In vivo 2D J-resolved magnetic resonance spectroscopy of rat brain with a 3-T clinical human scanner

Abstract

A clinical 3-T scanner equipped with a custom-made transmit/receive birdcage coil was used to collect 2D J-resolved single-voxel spectroscopy in vivo of rat brain. Four adult Wistar rats were scanned twice each, with a 2-week interval. Voxel size was approximately 5 × 10 × 5 mm 3. Total spectroscopic acquisition time was 14 min for collection of two 4:20 min water-suppressed acquisitions and one 4:20 min acquisition acquired in the absence of water suppression. The unsuppressed water data were used in post-processing to reduce residual water side bands, as well as for metabolite signal normalization to account for variations in coil loading and voxel size. Peak areas were estimated for resonances from N-acetyl aspartate (NAA), creatine, choline, taurine, glutamate, and combined glutamate and glutamine. T 2-relaxation times were estimated for NAA and creatine. The average deviation from the mean of repeated measures for glutamate, combined glutamate and glutamine, and taurine ranged from 7.6% to 18.3%, while for NAA, creatine, and choline, the deviation was less than 3%. The estimated T 2 values for NAA (mean ± SD = 330 ± 57 ms) and creatine (174 ± 27 ms) were similar to those reported previously for rat brain and for human gray and white matter. These results indicate that reliable, small animal brain MR spectroscopy can be performed on a human clinical 3-T scanner.