Multivoxel 3D proton spectroscopy in the brain at 1.5 versus 3.0 T: signal-to-noise ratio and resolution comparison.
OBJECTIVE
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 x 9 x 3 cm was obtained within a field of view of 16 x 16 x 3 cm that was partitioned into four (0.75-cm-thick) 16 x 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.


CONCLUSIONS
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.
Gonen
O
O
Fox Chase Cancer Center, Philadelphia, USA.
Gruber
S
S
Li
B S
BS
Mlynárik
V
V
Moser
E
E
D000328:Adult; D001921:Brain / Q000378:metabolism* / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male