Spatial Hadamard encoding of J-edited spectroscopy using slice-selective editing pulses

A new approach for simultaneous dual-voxel J-difference spectral editing is described, which uses spatially selective spectral-editing pulses and Hadamard encoding. A theoretical framework for spatial Hadamard editing and reconstruction for parallel acquisition (SHERPA) was developed, applying gradient pulses during the frequency-selective editing pulses. Spectral simulations were performed for either one (gamma-aminobutyric acid, GABA) or two molecules (glutathione and lactate) simultaneously detected in two voxels. The method was tested in a two-compartment GABA phantom, and finally applied to the left and right hemispheres of 10 normal control subjects, scanned at 3 T. SHERPA was successfully implemented at 3 T and gave results in close agreement with conventional MEGA-PRESS scans in both the phantom and in vivo experiments. Simulations for GABA editing for (3 cm)³ voxels in the left and right hemispheres suggest that both editing efficiency losses and contamination between voxels are about 2%. Compared with conventional single-voxel single-metabolite J-difference editing, two- or fourfold acceleration is possible without significant loss of SNR using the SHERPA method. Unlike some other dual-voxel methods, the method can be used with single-channel receiver coils, and there is no SNR loss due to unfavorable receive-coil geometry factors.