comparison of cardiac 31P MRS at 1.5 and 3 T

Abstract31P MRS was evaluated on normal volunteers at 1.5 and 3 T, and the signal‐to‐noise ratio (SNR) of the two field strengths was calculated. The in vivo spin‐lattice, T1, relaxation times for PCr and γ‐ATP, which are essential for correcting for the effects of radiofrequency saturation on the PCr/ATP ratio, were determined at 3 T. The T1 values for six volunteers were 3.8 ± 0.7 s for PCr (mean ± SD) and 2.4 ± 1.1 s for γ‐ATP, which are similar to reported values at 1.5 T, allowing us to use protocols developed at 1.5 T at the new clinical field strength of 3 T. Direct comparison between 1.5 T and 3 T in the same 10 subjects, using coils of identical geometry and identical pulse sequences gave a mean SNR for PCr at 3 T which was 206 ± 94% of that at 1.5 T. The linewidth for PCr increased from 13 ± 6 Hz at 1.5 T to 22 ± 12 Hz at 3 T. The coefficient of variation in the measurement of PCr/ATP, based on the Cramer–Rao lower bounds, was reduced from 32 ± 25% at 1.5 T to 18 ± 13% at 3 T. Thus, 31P MRS at 3 T is greatly improved by the increase in SNR compared with acquisitions at 1.5 T because of the higher field strength. Copyright © 2008 John Wiley & Sons, Ltd.