A fast variant of H-1 spectroscopic U-FLARE imaging using adjusted chemical shift phase encoding

So far, fast spectroscopic imaging (SI) using the U-FLARE sequence has prov ided metabolic maps indirectly via Fourier transformation (FT) along the ch emical shift (CS) dimension and subsequent peak integration. However, a lar ge number of CS encoding steps N-omega is needed to cover the spectral band width and to achieve sufficient spectral resolution for peak integration ev en if the number of resonance lines is small compared to N-omega and even i f only metabolic images are of interest and not the spectra in each voxel, Other reconstruction algorithms require extensive prior knowledge, starting values, and/or model functions. An adjusted CS phase encoding scheme (APE) can be used to overcome these drawbacks. It incorporates prior knowledge o nly about the resonance frequencies present in the sample. Thus, N-omega ca n be reduced by a factor of 4 for many H-1 in vivo studies while no spectra have to be reconstructed, and no additional user interaction, prior knowle dge, starting values, or model function are required. Phantom measurements and in vivo experiments on rat brain have been performed at 4.7 T to test t he feasibility of the method for proton SI. (C) 2000 Academic Press.