TY - JOUR
T1 - Regional neurochemical profiles in the human brain measured by 1H MRS at 7T using local B 1 shimming
AU - Emir, Uzay E.
AU - Auerbach, Edward J.
AU - van de Moortele, Pierre Francois
AU - Marjańska, Malgorzata
AU - Uǧurbil, Kamil
AU - Terpstra, Melissa
AU - Tkáč, Ivan
AU - Öz, Gülin
PY - 2012/1
Y1 - 2012/1
N2 - Increased sensitivity and chemical shift dispersion at ultra-high magnetic fields enable the precise quantification of an extended range of brain metabolites from 1H MRS. However, all previous neurochemical profiling studies using single-voxel MRS at 7T have been limited to data acquired from the occipital lobe with half-volume coils. The challenges of 1H MRS of the human brain at 7T include short T 2 and complex B 1 distribution that imposes limitations on the maximum achievable B 1 strength. In this study, the feasibility of acquiring and quantifying short-echo (TE=8ms), single-voxel 1H MR spectra from multiple brain regions was demonstrated by utilizing a 16-channel transceiver array coil with 16 independent transmit channels, allowing local transmit B 1 (B 1 +) shimming. Spectra were acquired from volumes of interest of 1-8mL in brain regions that are of interest for various neurological disorders: frontal white matter, posterior cingulate, putamen, substantia nigra, pons and cerebellar vermis. Local B 1 + shimming substantially increased the transmit efficiency, especially in the peripheral and ventral brain regions. By optimizing a STEAM sequence for utilization with a 16-channel coil, artifact-free spectra were acquired with a small chemical shift displacement error (<5% /ppm/direction) from all regions. The high signal-to-noise ratio enabled the quantification of neurochemical profiles consisting of at least nine metabolites, including γ-aminobutyric acid, glutamate and glutathione, in all brain regions. Significant differences in neurochemical profiles were observed between brain regions. For example, γ-aminobutyric acid levels were highest in the substantia nigra, total creatine was highest in the cerebellar vermis and total choline was highest in the pons, consistent with the known biochemistry of these regions. These findings demonstrate that single-voxel 1H MRS at ultra-high field can reliably detect region-specific neurochemical patterns in the human brain, and has the potential to objectively detect alterations in neurochemical profiles associated with neurological diseases.
AB - Increased sensitivity and chemical shift dispersion at ultra-high magnetic fields enable the precise quantification of an extended range of brain metabolites from 1H MRS. However, all previous neurochemical profiling studies using single-voxel MRS at 7T have been limited to data acquired from the occipital lobe with half-volume coils. The challenges of 1H MRS of the human brain at 7T include short T 2 and complex B 1 distribution that imposes limitations on the maximum achievable B 1 strength. In this study, the feasibility of acquiring and quantifying short-echo (TE=8ms), single-voxel 1H MR spectra from multiple brain regions was demonstrated by utilizing a 16-channel transceiver array coil with 16 independent transmit channels, allowing local transmit B 1 (B 1 +) shimming. Spectra were acquired from volumes of interest of 1-8mL in brain regions that are of interest for various neurological disorders: frontal white matter, posterior cingulate, putamen, substantia nigra, pons and cerebellar vermis. Local B 1 + shimming substantially increased the transmit efficiency, especially in the peripheral and ventral brain regions. By optimizing a STEAM sequence for utilization with a 16-channel coil, artifact-free spectra were acquired with a small chemical shift displacement error (<5% /ppm/direction) from all regions. The high signal-to-noise ratio enabled the quantification of neurochemical profiles consisting of at least nine metabolites, including γ-aminobutyric acid, glutamate and glutathione, in all brain regions. Significant differences in neurochemical profiles were observed between brain regions. For example, γ-aminobutyric acid levels were highest in the substantia nigra, total creatine was highest in the cerebellar vermis and total choline was highest in the pons, consistent with the known biochemistry of these regions. These findings demonstrate that single-voxel 1H MRS at ultra-high field can reliably detect region-specific neurochemical patterns in the human brain, and has the potential to objectively detect alterations in neurochemical profiles associated with neurological diseases.
KW - B shimming
KW - MRS
KW - Neurochemical profile
KW - Short TE
KW - Single voxel
KW - Transceiver array coil
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U2 - 10.1002/nbm.1727
DO - 10.1002/nbm.1727
M3 - Article
C2 - 21766380
AN - SCOPUS:84855874072
SN - 0952-3480
VL - 25
SP - 152
EP - 160
JO - NMR in biomedicine
JF - NMR in biomedicine
IS - 1
ER -