Human cardiac<sup>31</sup>P magnetic resonance spectroscopy at 7 tesla
Rodgers CT., Clarke WT., Snyder C., Vaughan JT., Neubauer S., Robson MD.
Purpose Phosphorus magnetic resonance spectroscopy (31P-MRS) affords unique insight into cardiac energetics but has a low intrinsic signal-to-noise ratio (SNR) in humans. Theory predicts an increased31P-MRS SNR at 7T, offering exciting possibilities to better investigate cardiac metabolism. We therefore compare the performance of human cardiac31P-MRS at 7T to 3T, and measure T1s for31P metabolites at 7T. Methods Matched31P-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, γ-ATP 1.82 ± 0.09s, α-ATP 1.39 ± 0.09s, β-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 2.8× at 7T relative to 3T, the Cramer-Ráo uncertainty (CRLB) in PCr concentration decreased 2.4×, the mean CRLB in PCr/ATP decreased 2.7× and the PCr/ATP SD decreased 2×. Conclusion Cardiac31P-MRS at 7T has higher SNR and the spectra can be quantified more precisely than at 3T. Cardiac31P T1s are shorter at 7T than at 3T. We predict that 7T will become the field strength of choice for cardiac31P-MRS. Magn Reson Med 72:304-315, 2014. © 2013 Wiley Periodicals, Inc. Copyright © 2013 Wiley Periodicals, Inc.