Regional neurochemical profiles in the human brain measured by 1H MRS at 7T using local B 1 shimming

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Abstract

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.

Original languageEnglish (US)
Pages (from-to)152-160
Number of pages9
JournalNMR in biomedicine
Volume25
Issue number1
DOIs
StatePublished - Jan 1 2012

Fingerprint

Brain
Aminobutyrates
Pons
Chemical shift
Substantia Nigra
Metabolites
Occipital Lobe
Biochemistry
Proton Magnetic Resonance Spectroscopy
Creatine
Putamen
Gyrus Cinguli
Signal-To-Noise Ratio
Magnetic Fields
Choline
Nervous System Diseases
Transceivers
Artifacts
Glutathione
Glutamic Acid

Keywords

  • B shimming
  • MRS
  • Neurochemical profile
  • Short TE
  • Single voxel
  • Transceiver array coil

Cite this

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title = "Regional neurochemical profiles in the human brain measured by 1H MRS at 7T using local B 1 shimming",
abstract = "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.",
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author = "Emir, {Uzay E.} and Auerbach, {Edward J} and {Van de Moortele}, Pierre-Francois and Malgorzata Marjanska and Kamil Ugurbil and Melissa Terpstra and Ivan Tkac and Gulin Oz",
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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 - Marjanska, Malgorzata

AU - Ugurbil, Kamil

AU - Terpstra, Melissa

AU - Tkac, Ivan

AU - Oz, Gulin

PY - 2012/1/1

Y1 - 2012/1/1

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.

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KW - Short TE

KW - Single voxel

KW - Transceiver array coil

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