Parametric multiecho proton spectroscopic imaging: application to the rat brain in vivo.

A parametric multiecho variant of proton spectroscopic imaging (SI) is presented using a multiecho SI sequence with uniform phase-encoding of all echoes within each echo train. The acquisition of SI data sets at different echo times (TE) increases the amount of information obtained within the same total measuring time as in standard SI measurements. The gain in information can be used: (a) to choose the most appropriate TE for each metabolite signal with respect to T2, spin coupling, or problems caused by peak overlap; (b) to measure the relaxation time T2 of metabolite signals with high spatial resolution; or (c) to improve the signal-to-noise ratio for metabolite signals with long T2 values by adding spectra calculated from consecutive echoes. The method was tested in vivo on healthy rat brain and applied to study metabolic changes in rat brain lesions.