Reduction of B(0) inhomogeneity effects in triple-quantum-filtered sodium imaging.

Triple-quantum (TQ) filtered sodium MR imaging has been proposed for separation of sodium signal arising from different physiological compartments. In a three-pulse sequence without refocussing pulse, the TQ signal is strongly sensitive to inhomogeneities of the B(0) field. We examine the dependence of the TQ signal intensity on the sequence parameters and propose a modified phase-cycling scheme to improve image quality. A new method for correction of B(0) inhomogeneity artefacts in TQ filtered sodium imaging is presented which requires only two acquisitions to obtain a correction as far as the B(0) inhomogeneity and the pulse widths are not too large. The method was verified in phantom experiments.