Proton Magnetic Resonance Spectroscopic Imaging (MRSI) enables the distribution of a number of MR-observable tissue metabolites to be mapped, offering considerable clinical potential as a diagnostic imaging technique. However, for brain studies, the spatial extent of the available information has been limited by acquisition time constrains, and the necessity to avoid signal contamination from subcutaneous lipid regions. The goal of this project is the measurement of 3D brain metabolite distributions over a large volume that includes cortical surface regions, and with high spatial resolution. This will be achieved by the development of a 1H MRSI method that uses rapid acquisition combined with a dual-density k-space sampling distribution, that simultaneously provides high-sensitivity for metabolite distributions and high spatial resolution for subcutaneous lipid regions. Post-processing methods will be used to further diminish ringing and contamination from subcutaneous lipid signals, and motion artifacts. High-resolution mapping for metabolites will be obtained using a multiple session protocol that accounts for variable subject position. This work will greatly extend the clinical applications of MRSI by providing volumetric metabolite distributions over a wide region of the brain, with high sensitivity. As techniques are developed, they will support ongoing clinical studies investigating changes of brain metabolites associated with Alzheimer's disease and aging, epilepsy, substance abuse, and schizophrenia.
