PROJECT SUMMARY Edited magnetic resonance spectroscopy allows the non-invasive detection of low-concentration metabolites within the brain, free from overlap from other, more abundant compounds. Until recently, spectral- editing techniques have generally focused on measuring individual metabolites in one brain region at a time (for instance, the well-known ‘MEGA-PRESS’ method). However, this is a time-consuming approach which severely limits clinical applicability when multiple metabolites and/or brain regions are involved. The main goal of this proposal is therefore to develop and establish the reproducibility edited experiments that can detect multiple edited molecules in multiple brain regions, all within a single acquisition. We will develop multi-voxel localization techniques to combine with our recently developed multi-metabolite editing methods, including the Hadamard-encoded ‘HERMES’ approach as well as the new ‘HERCULES’ method which allows for up to 13 metabolites to be simultaneously determined. For applications that may require a limited number of voxels to be acquired, we will developed multi-band excitation and parallel acquisition ‘PRIAM’ methods in combination with HERMES and HERCULES. For applications that require greater spatial coverage and/or the ability to map out the spatial distribution of metabolite levels, edited MR spectroscopic imaging (MRSI) techniques will be developed for use in combination with HERMES and HERCULES editing. Since edited-MRSI is very sensitive to head motion and other instabilities, acquisition and processing methods will be implemented for robust, motion-insensitive edited-MRSI. Rigor and reproducibility will be carefully assessed; newly developed methodologies will be validated by comparison to conventional measurements in the same subjects. Expected improvements in temporal signal- to-noise ratios and reproducibility will also be measured. The resulting data acquisition and analysis tools will be made available for dissemination to the clinical neuroscience and neuroimaging communities.

PROJECT NARRATIVE Magnetic resonance spectroscopy (MRS) can measure the concentration of naturally occurring chemicals within the brain, often applying ‘edited’ methods which focus on one particular chemical and location. This project will develop new experimental methods that allow the simultaneous measurement of several chemicals simultaneously in multiple regions of the brain. The methods developed in this study will be disseminated to the neuroimaging community, and are expected to have a wide range of clinical and neuroscience applications.