Comparison of methods for reduction of lipid contamination for in vivo proton MR spectroscopic imaging of the brain.

In vivo proton MR spectroscopic imaging (MRSI) of human brain is complicated by the presence of a strong signal from subcutaneous lipids, which may result in signal contamination in metabolite images obtained following Fourier-transform reconstruction. In this study, two approaches for reduction of lipid contamination--using postprocessing and additional data acquisition--are compared. The first uses extrapolation of k-space information for subcutaneous lipid, which has been applied to data obtained using conventional fully phase-encoded MRSI with circularly sampled k-space or echo-planar spectroscopic imaging (EPSI). The second uses a dual EPSI technique that combines multiple-averaged central k-space data with a single EPSI acquisition of additional information that is used for improved lipid reconstruction. Comparisons are carried out with data obtained from human brain in vivo at 1.5 T with short and medium TEs. Results demonstrate that the performance of both methods for reducing the effects of lipid contamination is similar, and that both are limited by the effects of instrumental instabilities and subject motion, which also depend on the acquisition method used.