Human Cardiac 31P Magnetic Resonance Spectroscopy at 7 Tesla

Purpose: Phosphorus magnetic resonance spectroscopy (P-31-MRS) affords unique insight into cardiac energetics but has a low intrinsic signal-to-noise ratio (SNR) in humans. Theory predicts an increased P-31-MRS SNR at 7T, offering exciting possibilities to better investigate cardiac metabolism. We therefore compare the performance of human cardiac (PMRS)-P-31 at 7T to 3T, and measure T1s for P-31 metabolites at 7T. Methods: Matched P-31-MRS data were acquired at 3T and 7T, on nine normal volunteers. A novel Look-Locker CSI acquisition and fitting approach was used to measure T1s on six normal volunteers. Results: T1s in the heart at 7T were: phosphocreatine (PCr) 3.05 +/- 0.41s, g-ATP 1.82 +/- 0.09s, alpha-ATP 1.39 +/- 0.09s, beta-ATP 1.02 +/- 0.17s and 2,3-DPG (2,3-diphosphoglycerate) 3.05 +/- 0.41s (N = 6). In the field comparison (N = 9), PCr SNR increased 2.8x at 7T relative to 3T, the Cramer-Rao uncertainty (CRLB) in PCr concentration decreased 2.4x, the mean CRLB in PCr/ATP decreased 2.7x and the PCr/ATP SD decreased 2x. Conclusion: Cardiac P-31-MRS at 7T has higher SNR and the spectra can be quantified more precisely than at 3T. Cardiac P-31 T1s are shorter at 7T than at 3T. We predict that 7Twill become the field strength of choice for cardiac P-31-MRS. (C) 2013 Wiley Periodicals, Inc.