In vivo proton magnetic resonance spectroscopic imaging of the healthy human brain at 9.4 T: initial experience
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In this study, the feasibility of in vivo proton magnetic resonance spectroscopic imaging (1H MRSI) of the healthy human brain at a field strength of 9.4 T, using conventional acquisition techniques, is examined and the initial experience is summarized.
Materials and methods
MRSI measurements were performed on a 9.4 T MR scanner (Siemens, Erlangen, Germany) equipped with head-only gradient insert (AC84, Siemens) and custom-developed, 8-channel transmit/24-channel receive, and 16-channel transmit/31-channel receive coils. Spectra were acquired from the superior part of the human brain with a modified STEAM sequence. Spectral quantification was done with LCModel software.
Reasonable quality and signal-to-noise ratio of the acquired spectra allowed reliable quantification of 12 metabolites (Cramer-Rao lower bounds < 20 %), some of which may be difficult to quantify at field strengths below 7 T due to overlapping resonances or low concentrations.
While further developments are necessary to minimize chemical shift displacement and homogeneity of the transmit field, it is demonstrated that in vivo 1H MRSI at a field strength of 9.4 T is possible. However, further studies applying up-to-date techniques to overcome high-field specific problems are needed in order to assess the potential gain in sensitivity that may be offered by MRSI at 9.4 T.
KeywordsSpectroscopic imaging Ultra-high magnetic field Human brain Chemical shift displacement Transmit field inhomogeneities
This work was founded (in part) by the Helmholtz Alliance ICEMED—Imaging and Curing Environmental Metabolic Diseases, through the Initiative and Networking Found of the Helmholtz Association.
Conflict of interest
The authors declare that they have no conflict of interest.
All volunteer studies have been approved by the local ethics committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
All in vivo measurements described in this study were conducted exclusively on healthy volunteers. All volunteers gave their informed consent prior to their inclusion in the study.
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