Localized 1H NMR spectroscopy in different regions of human brain in vivo at 7 T: T2 relaxation times and concentrations of cerebral metabolites

Abstract

At the high field strength of 7 T, in vivo spectra of the human brain with exceptional spectral quality sufficient to quantify 16 metabolites have been obtained previously only in the occipital lobe. However, neurochemical abnormalities associated with many brain disorders are expected to occur in brain structures other than the occipital lobe. The purpose of the present study was to obtain high-quality spectra from various brain regions at 7 T and to quantify the concentrations of different metabolites. To obtain concentrations of metabolites within four different regions of the brain, such as the occipital lobe, motor cortex, basal ganglia and cerebellum, the T(2) relaxation times of the singlets and J-coupled metabolites in these regions were measured for the first time at 7 T. Our results demonstrate that high-quality, quantifiable spectra can be obtained in regions other than the occipital lobe at 7 T utilizing a 16-channel transceiver coil and B(1)(+) shimming.

Copyright © 2011 John Wiley & Sons, Ltd.

Figures

Figure 1

LCModel quantification of the representative 1H NMR spectra obtained at 7 T with a modified LASER sequence from the four following regions of the human brain: (a) a 19.7 mL voxel placed in the occipital lobe (OC), (b) an 8 mL voxel placed in the motor cortex (MC), (c) a 9 mL voxel placed in the basal ganglia (BG), and (d) a 15.6 mL voxel placed in the cerebellum. In all spectra, TR = 4.5 s, TE = 35 ms, NS = 128, and no line-broadening was applied. The location and size of the voxels are shown on T2-weighted images.

Figure 2

The relative transmit efficiency before and after local B1+ phase shimming, optimized for the following regions of interest: (a) OC, (b) MC, (c) BG, and (d) CR. The average gain and standard deviation (n = 5) in the transmit efficiency is listed next to each image.

Figure 3

Representative 1H NMR spectra obtained at 7 T with a modified LASER sequence from the 19.7 mL voxel placed in the human occipital lobe. For the spectra, TR = 4.5 s, NS = 64, and no line-broadening was applied.