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 ( 31 P-MRS) affords unique insight into cardiac energetics but has a low intrinsic signal-to-noise ratio (SNR) in humans. Theory predicts an increased 31 P-MRS SNR at 7T, offering exciting possibilities to better investigate cardiac metabolism. We therefore compare the performance of human cardiac 31 P-MRS at 7T to 3T, and measure T 1 s for 31 P metabolites at 7T. Methods Matched 31 P-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 T 1 s on six normal volunteers. Results T 1 s 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 Cardiac 31 P-MRS at 7T has higher SNR and the spectra can be quantified more precisely than at 3T. Cardiac 31 P T 1 s are shorter at 7T than at 3T. We predict that 7T will become the field strength of choice for cardiac 31 P-MRS. Magn Reson Med 72:304-315, 2014. © 2013 Wiley Periodicals, Inc. Copyright © 2013 Wiley Periodicals, Inc.