Abstract
BACKGROUND AND PURPOSE: The new 3.0-T imagers theoretically yield double the signal-to-noise ratio (SNR) and spectral resolution of 1.5-T instruments. To assess the possible improvements for multivoxel 3D proton MR spectroscopy (1H-MRS) in the human brain, we compared the SNR and spectral resolution performance with both field strengths.
METHODS: Three-dimensional 1H-MRS was performed in four 21–29-year-old subjects at 1.5 and 3.0 T. In each, a volume of interest of 9 × 9 × 3 cm was obtained within a field of view of 16 × 16 × 3 cm that was partitioned into four (0.75-cm-thick) 16 × 16-voxel sections, yielding 324 (0.75-cm3) signal voxels per examination.
RESULTS: In an acquisition protocol of approximately 27 min, average voxel SNRs increased 23–46% at 3.0 versus 1.5 T in the same brain regions of the same subjects. SNRs for N-acetylaspartate, creatine, and choline, respectively, were as follows: 15.3 ± 4, 8.2 ± 2.2, and 8.0 ± 2.0 at 1.5 T and 22.4 ± 7.0, 10.1 ± 3.5, and 10.1 ± 3.6 at 3.0 T. Spectral resolution (metabolite linewidths) were 3.5 ± 0.5 Hz at 1.5 T versus 6.1 ± 1.5 Hz at 3.0 T in approximately 900 voxels. Spectral baselines were noticeably flatter at 3.0 T.
CONCLUSION: Expected gains in SNR and spectral resolution were not fully realized in a realistic experiment because of intrinsic and controllable factors. However, the 23–46% improvements obtained enable more reliable peak-area estimation and an 1H-MRS acquisition approximately 50% shorter at 3.0 versus 1.5 T.
- Copyright © American Society of Neuroradiology
