Correction of local B0 shifts in 3D EPSI of the human brain at 4 T.
High-spatial-resolution acquisition (HR) was previously proposed for 3D echo-planar spectroscopic imaging (EPSI) in combination with a high-spatial-resolution water reference EPSI data set to minimize inhomogeneous spectral line broadening, allowing for local frequency shift (B(0) shift) correction in human brain metabolite maps at 1.5 T (Ebel A et al., Magn. Reson. Imaging 21:113-120, 2003). At a higher magnetic field strength, B(0), increased field inhomogeneities typically lead to increased line broadening. Additionally, increased susceptibility variations render shimming of the main magnetic field over the whole head more difficult. This study addressed the question whether local B(0)-shift correction still helps limit line broadening in whole-brain 3D EPSI at higher magnetic fields. The combination of HR and local B(0)-shift correction to limit line broadening was evaluated at 4 T. Similar to the results at 1.5 T, the approach provided a high yield of voxels with good spectral quality for 3D EPSI, resulting in improved brain coverage.
Ebel
Andreas
A
Northern California Institute for Research and Education, DVA Medical Center San Francisco, MR Unit (114M), 4150 Clement St., San Francisco, CA 94121, USA. andreas.ebel@ucsf.edu
Maudsley
Andrew A
AA
Schuff
Norbert
N
D000465:Algorithms; D016477:Artifacts; D015415:Biomarkers / Q000378:metabolism; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D015415:Biomarkers; D011522:Protons