| Magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopic imaging (1H MRSI) are valuable, noninvasive techniques that reveal structural and metabolic information about the human body. Operating at high magnetic fields offers the advantages of increased signal-to-noise ratio, which may be used to reduce scan times or improve spatial resolution, and improved spectral resolution. However, B1 inhomogeneity, B 0 inhomogeneity and chemical shift localization errors significantly limit the performance of MRI and 1H MRSI at high fields. This work focuses on three techniques that overcome these limitations in order to utilize the benefits of high-field MR. The first is a Point Resolved Spectroscopy sequence with adiabatic spatial-spectral refocusing pulses for 1H MRSI at 7T. The sequence acquires multiple narrow spectral bands in an interleaved fashion and provides magnetization profiles that are largely invariant for a range of B1 values and chemical shifts. The second is a pair of spectrally selective inversion pulses for 1H MRSI that achieve B1-insensitive fat suppression without degrading signal from the major metabolites of interest. The final technique is a slice-selective adiabatic excitation pulse that stays within RF amplitude and gradient limits on most human scanners. The pulse may be used in many high-field pulse sequences. |
