B0 magnetic field homogeneity and shimming for in vivo magnetic resonance spectroscopy

The homogenization of B0 conditions is necessary for every magnetic resonance spectroscopy (MRS) investigation. Its direct consequence is narrow spectral lines, on which reliable separation and quantification of biochemicals, and thus experimentally obtainable metabolic information, fundamentally relies. Besides spectral linewidth, unwanted B0 inhomogeneity also impairs other aspects of the MRS experiment, such as water suppression and editing efficiency, that rely on exact frequency definition. Therefore, experimental B0 homogenization, called B0 shimming, is mandatory for meaningful MRS, and high-level B0 shimming is arguably one of the most important ingredients for successful MRS investigations. In this review, we describe the relevance of B0 homogeneity for in vivo MRS and summarize common concepts and specific solutions for its experimental optimization.