Generalization of Phase-Encoded NMR Chemical Shift Imaging

An echo-time encoding NMR chemical shift imaging proposed by Dixon is generalized to be applicable to multiline chemical shift imaging. The method utilizes the phase differences among nuclei encoded by shifting the position of the rf pulse in the spin echo sequence to resolve chemical shift images. The inevitable phase error caused by the static field inhomogeneity is corrected by using phase images of phantom images measured under the same conditions as the actual measurements. The minimum number of encodings can be reduced to half the number of chemical shifts without sacrificing spatial resolution. The experiments were carried out for 3-line 1H chemical shifts using benzene, water, and acetone at 0.5 T. All the chemical shift images could be clearly resolved with only two scans when the field inhomogeneity was larger than the maximum chemical shift difference.