Fast volumetric spatial-spectral MR imaging of hyperpolarized ^(13)C-labeled compounds using multiple echo 3D bSSFP

Purpose: The goal of this work was to develop a fast 3D chemical shift imaging technique for the noninvasive measurement of hyperpolarized ^(13)C-labeled substrates and metabolic products at low concentration. Materials and Methods: Multiple echo 3D balanced steady state magnetic resonance imaging (ME-3DbSSFP) was performed in vitro on a syringe containing hyperpolarized [1,3,3-2H3; 1-^(13)C]2-hydroxyethylpropionate (HEP) adjacent to a ^(13)C-enriched acetate phantom, and in vivo on a rat before and after intravenous injection of hyperpolarized HEP at 1.5 T. Chemical shift images of the hyperpolarized HEP were derived from the multiple echo data by Fourier transformation along the echoes on a voxel by voxel basis for each slice of the 3D data set. Results: ME-3DbSSFP imaging was able to provide chemical shift images of hyperpolarized HEP in vitro, and in a rat with isotropic 7-mm spatial resolution, 93 Hz spectral resolution and 16-s temporal resolution for a period greater than 45 s. Conclusion: Multiple echo 3D bSSFP imaging can provide chemical shift images of hyperpolarized ^(13)C-labeled compounds in vivo with relatively high spatial resolution and moderate spectral resolution. The increased signal-to-noise ratio of this 3D technique will enable the detection of hyperpolarized ^(13)C-labeled metabolites at lower concentrations as compared to a 2D technique.