In vivo proton T-1 relaxation times of mouse myocardial metabolites at 9.4 T

PurposeProton magnetic resonance spectroscopy (H-1-MRS) for quantitative in vivo assessment of mouse myocardial metabolism requires accurate acquisition timing to minimize motion artifacts and corrections for T-1-dependent partial saturation effects. In this study, mouse myocardial water and metabolite T-1 relaxation time constants were quantified. MethodsCardiac-triggered and respiratory-gated PRESS-localized H-1-MRS was employed at 9.4 T to acquire signal from a 4-mu L voxel in the septum of healthy mice (n=10) while maintaining a steady state of magnetization using dummy scans during respiratory gates. Signal stability was assessed via standard deviations (SD) of zero-order phases and amplitudes of water spectra. Saturation-recovery experiments were performed to determine T-1 values. ResultsPhase SD did not vary for different repetition times (TR), and was 13.1 degrees 4.5 degrees. Maximal amplitude SD was 14.2%+/- 5.1% at TR=500 ms. Myocardial T-1 values (mean +/- SD) were quantified for water (1.71 +/- 0.25 s), taurine (2.18 +/- 0.62 s), trimethylamine from choline-containing compounds and carnitine (1.67 +/- 0.25 s), creatine-methyl (1.34 +/- 0.19 s), triglyceride-methylene (0.60 +/- 0.15 s), and triglyceride-methyl (0.90 +/- 0.17 s) protons. ConclusionThis work provides in vivo quantifications of proton T-1 values for mouse myocardial water and metabolites at 9.4 T. Magn Reson Med 73:2069-2074, 2015. (c) 2014 Wiley Periodicals, Inc