Improved quantification precision of human brain short echo-time (1) H magnetic resonance spectroscopy at high magnetic field: a simulation study.

PURPOSE

The gain in quantification precision that can be expected in human brain (1) H MRS at very high field remains a matter of debate. Here, we investigate this issue using Monte-Carlo simulations.

METHODS

Simulated human brain-like (1) H spectra were fitted repeatedly with different noise realizations using LCModel at B0 ranging from 1.5T to 11.7T, assuming a linear increase in signal-to-noise ratio with B0 in the time domain, and assuming a linear increase in linewidth with B0 based on experimental measurements. Average quantification precision (Cramér-Rao lower bound) was then determined for each metabolite as a function of B0 .

RESULTS

For singlets, Cramér-Rao lower bounds improved (decreased) by a factor of ∼ B0 as B0 increased, as predicted by theory. For most J-coupled metabolites, Cramér-Rao lower bounds decreased by a factor ranging from B0 to B0 as B0 increased, reflecting additional gains in quantification precision compared to singlets owing to simplification of spectral pattern and reduced overlap.

CONCLUSIONS

Quantification precision of (1) H magnetic resonance spectroscopy in human brain continues to improve with B0 up to 11.7T although peak signal-to-noise ratio in the frequency domain levels off above 3T. In most cases, the gain in quantification precision is higher for J-coupled metabolites than for singlets.