Metabolic MR imaging of regional triglyceride and creatine content in the human heart

Abstract

An optimized echo-planar spectroscopic imaging sequence is proposed to facilitate spatial mapping of triglyceride and total creatine content in the human heart. The sequence integrates local-look field of view reduction, cardiac and respiratory gating, and dedicated reconstruction steps to account for gradient channel delays, field inhomogeneity, and phase incoherence due to residual motion. The technique is demonstrated in 12 volunteers in comparison to single voxel point-resolved spectroscopy in the septal wall at 1.5 T. Triglyceride-to-water and total creatine-to-water ratios derived from echo-planar spectroscopic imaging (0.48 ± 0.18% and 0.06 ± 0.03%) and point-resolved spectroscopy (0.52 ± 0.17% and 0.07 ± 0.02%) were found to agree well. In the septal region, intraclass correlation coefficients ranging from 0.67 to 0.72 were estimated. A relatively weak agreement (intraclass correlation coefficients: 0.34 and 0.52) was found for sectors in the lateral wall due to field gradients induced by the posterior vein and limited sensitivity of the receive coil array in this area. On the basis of the findings, it is concluded that fast spectroscopic imaging of both cardiac triglyceride and total creatine content is feasible. Shimming and sensitivity challenges in the lateral region remain, however, to be addressed.