In vivo proton metabolite maps using the MESA 3D technique.
In vivo proton spectroscopy requires excellent static magnetic field homogeneity in order to allow suppression of the water signal. This is usually accomplished by restricting the observed signal to a small volume element, or voxel. However, the disadvantage of all single-voxel techniques is that each experiment results in a spectrum from only a single small region of the patient. This makes it difficult to map metabolite concentrations over extended regions of the patient's anatomy. Standard phase-encoding techniques that cover the entire sensitive volume of the receiver coil can provide metabolite maps but suffer from excessive field inhomogeneity and/or susceptibility problems at interfaces. We report here on a technique which localizes a large voxel within the patient and uses phase encoding within this voxel to obtain metabolite maps over an extended region of the patient's anatomy. Phantom results are presented to demonstrate the performance of the technique. In vivo results on human brains are also presented.