T2 estimation of downfield metabolites in human brain at 7T

The upfield part of the spectrum has thus far been well-characterized using magnetic resonance spectroscopy; however, the downfield part at 5-10ppm remains less so, particularly in humans. This work aims to improve metabolite characterization by calculating the T2’s of peaks downfield in grey matter at 7 T. We fitted downfield spectra to a heuristic model and obtained T2’s for several peaks of interest; the T2’s are all fairly similar, but significantly shorter than those reported for upfield peaks in the brain, which are approximately 70ms or longer depending on the structure

Elucidation of the downfield spectrum of human brain at 7T using multiple inversion recovery delays and echo times

Characterization of the full 1H spectrum may allow for better monitoring of pathologies and metabolism in humans. The downfield part (5-10ppm) is currently less well characterized than upfield; this work aims to benefit from higher field strength in order to quantify T1 and T2 in the downfield spectrum in human grey matter at 7T. We fitted downfield spectra to a heuristic model and obtained relaxation times for twelve peaks of interest. The T1’s are higher than those at 3T downfield; peaks with lower T1’s may include macromolecules. The T2’s are mostly shorter than those reported for upfield peaks at 7T

Downfield MR Spectroscopy at Ultrahigh Magnetic Fields

Introduction: Magnetic resonance spectroscopy benefits from using ultrahigh field scanners, as both the signal to noise ratio (SNR) and the separation of peaks improve. Inclusion of the downfield part of the spectrum (left of water peak) in addition to the generally used upfield part of the 1H MR spectrum is expected to allow for better monitoring of pathologies and metabolism in humans. The downfield part at 5-10ppm is less well characterized than the upfield spectrum, although some data is available for animal brain at high fields, as well as human brain at 3T. Experiments have been performed to elucidate the downfield spectrum in human brain and to quantify metabolite relaxation times T1 and T2 in grey matter at 7T using series of spectra with variable inversion recovery (IR) and echo time (TE) delays. Initial downfield experiments have also been performed in humans at 9.4T. Materials and Methods: Acquisition methods at 7T used a Philips 7T whole body scanner (UZH/ETH Zürich), with a voxel of interest placed in the visual cortex. A series of TEs and IRs was acquired in a total of 22 healthy volunteers. At 9.4T, spectra were acquired in three healthy volunteers on a Siemens whole-body MRI scanner (MPI Tuebingen). Results and Discussion: The spectra acquired at 7T and 9.4T demonstrate significant improvements in SNR and peak separation compared to those at lower field strengths. The averaged data sets from the 7T series were combined to develop a spectral model of partially overlapping signals this heuristic model describes the experimental data well and the results for many of the peaks are very consistent across subjects. T1 values found at 7T are mostly higher than those found at 3T, in particular for the NAA peak. Several peaks show a particularly short T1 in comparison to the others, indicating that they predominantly originate from macromolecules. The T2 values are in general much shorter than those found for upfield peaks