In vivo ¹H NMR spectroscopy of the human brain at 9.4 T: Initial results

In vivo proton NMR spectroscopy allows non-invasive detection and quantification of a wide range of biochemical compounds in the brain. Higher field strength is generally considered advantageous for spectroscopy due to increased signal-to-noise and increased spectral dispersion. So far ¹H NMR spectra have been reported in the human brain up to 7 T. In this study we show that excellent quality short echo time STEAM and LASER ¹H NMR spectra can be measured in the human brain at 9.4 T. The information content of the human brain spectra appears very similar to that measured in the past decade in rodent brains at the same field strength, in spite of broader linewidth in human brain. Compared to lower fields, the T ₁ relaxation times of metabolites were slightly longer while T ₂ relaxation values of metabolites were shorter (<100 ms) at 9.4 T. The linewidth of the total creatine (tCr) resonance at 3.03 ppm increased linearly with magnetic field (1.35 Hz/T from 1.5 T to 9.4 T), with a minimum achievable tCr linewidth of around 12.5 Hz at 9.4 T. At very high field, B ₀ microsusceptibility effects are the main contributor to the minimum achievable linewidth.