Metabolite-cycled echo-planar spectroscopic imaging of the human heart

Abstract

Purpose: Spectroscopic imaging could provide insights into regional cardiac triglyceride variations, but is hampered by relatively long scan times. It is proposed to synergistically combine echo-planar spectroscopic imaging (EPSI) with motion-adapted gating, weighted acquisition and metabolite cycling to reduce scan times to less than 10 min while preserving spatial-spectral quality. The method is compared to single-voxel measurements and to metabolite-cycled EPSI with conventional acquisition for assessing triglyceride-to-water (TG/W) ratios in the human heart. Methods: Measurements were performed on 10 healthy volunteers using a clinical 1.5T system. EPSI data was acquired both without and with motion-adapted gating in combination with weighted acquisition to assess TG/W ratios and relative Cramér-Rao lower bounds (CRLB) of TG. For comparison, single-voxel (PRESS) spectra were acquired in the interventricular septum. Results: Bland–Altman analyses did not show a significant bias in TG/W when comparing both metabolite-cycled EPSI methods to PRESS for any of the cardiac segments. Scan time was 8.05 ± 2.06 min and 17.91 ± 3.93 min for metabolite-cycled EPSI with and without motion-adapted gating and weighted acquisition, respectively, while relative CRLB of TG did not differ significantly between the two methods for any of the cardiac segments. Conclusions: Metabolite-cycled EPSI with motion-adapted gating and weighted acquisition allows detecting TG/W ratios in different regions of the in vivo human heart. Scan time is reduced by more than 2-fold to less than 10 min as compared to conventional acquisition, while keeping the quality of TG fitting constant.