Experimental method to eliminate frequency modulation sidebands in localized in vivo 1H MR spectra acquired without water suppression

An experimental method is described to eliminate frequency modulation sidebands in localized in vivo proton MR spectra acquired without water suppression. Based on the fact that the phases of the sideband artifact signals are coherent with the phases of the gradient pulses, the proposed method measures and combines signals with sequences using opposite gradients to cancel the sidebands. Factors effecting the results of the cancellation are investigated. Optimized cancellation is achieved by trimming the refocusing gradients, optimizing the spoiler gradients, or replacing the spoiler gradients with a 16-step RF phase cycling. The performance of the method is demonstrated by phantom and in vivo experiments on the healthy rat brain. (C) 2004 Wiley-Liss, Inc.