B0-adjusted and sensitivity-encoded spectral localization by imaging (BASE-SLIM) in the human brain in vivo.

Spectral localization by imaging (SLIM) based magnetic resonance spectroscopy (MRS) provides a framework that overcomes major limitations of current MRS techniques, which allow only rectangular voxel shapes that do not conform to the shapes of brain structures or lesions. However, the restrictive assumption of compartmental homogeneity in SLIM can lead to localization errors, thus its applications have been very limited to date. SLIM-based localization is subject to errors due to inhomogeneous B0 and B1 fields, particularly in organs with complex compartmental geometry including the human brain. The limitations of SLIM were overcome through the development and implementation of B0-adjusted and sensitivity-encoded SLIM (BASE-SLIM) that includes corrections for inhomogeneities of both B0 and B1 fields throughout the volume of interest. In this study, we demonstrate significantly improved localization accuracy in compartments with arbitrary shapes and reliable quantification of metabolite concentrations in gray and white matter of the human brain using the BASE-SLIM technique.