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  Free induction decay proton magnetic resonance spectroscopic imaging in the healthy human brain at 9.4 Tesla: initial results

Chadzynski, G., Bause, J., Hagberg, G., Shajan, G., Pohmann, R., Engelmann, J., et al. (2015). Free induction decay proton magnetic resonance spectroscopic imaging in the healthy human brain at 9.4 Tesla: initial results. Poster presented at 10th Annual Meeting of the European Society for Molecular Imaging (EMIM 2015), Tübingen, Germany.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-002A-471E-3 Version Permalink: http://hdl.handle.net/21.11116/0000-0000-F83E-4
Genre: Poster

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 Creators:
Chadzynski, G1, Author              
Bause, J1, Author              
Hagberg, GE1, 2, Author              
Shajan, G1, Author              
Pohmann, R1, 3, Author              
Engelmann, J1, Author              
Scheffler, K1, Author              
Affiliations:
1Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497796              
2Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497798              
3Dept. Empirical Inference, Max Planck Institute for Intelligent Systems, Max Planck Society, ou_1497647              

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 Abstract: Introduction Recent studies at ultra-high field [1,2] show that FID based MR spectroscopic imaging (FID-MRSI) avoids in-plane chemical shift displacement and minimizes T2 related signal losses. Yet, FID-MRSI spectra suffer from lipid contaminations (arising from subcutaneous fatty tissue) and phase distortions, caused by the FID truncation (due to the acquisition delay necessary for the excitation pulse and gradients). Our aim was to examine the feasibility of FID-MRSI of the healthy human brain at 9.4T. In the presented approach the missing FID points were reconstructed with an autoregressive model [3] and the lipid contaminations were minimized by improving the point spread function which was achieved by increasing the spatial resolution and Hamming filter as in [2]. Total acquisition time of FID-MRSI sequence was shortened by optimizing the water suppression (water suppression enhanced through T1 effects-WET) [4] scheme. Methods Spectra were collected at a 9.4T MR scanner (Siemens, Erlangen, Germany) using a custom built coil [5]. Water suppressed spectra (with original and optimized WET) were acquired from the brain of two volunteers. In-vivo measurements were approved by the local ethical committee. Acquisition parameters: TR: 340 and 240ms (original and optimized WET, respectively), acquisition delay: 2.3ms, 64×64 voxels, acquisition duration: 128ms, spectral bandwidth: 4kHz, nominal voxel size 3.1×3.1×10mm. These acquisition parameters resulted in a total acquisition time of 21 (original) and 15 min (optimized WET). Results The remaining water signal after suppression is depicted in Fig.1. It can be seen that in the case of optimized WET (c), not only the residual water signal is smaller, but also the suppression is more homogenous against B1+ variations (a). Acquisition at high in-plane resolution combined with Hamming filtering minimized contaminations with lipid signals. This was even the case for voxels closely located to the skull (Fig. 2, graphs 14), where the spectral range of interest between 2 and 4 ppm was unaffected. Conclusions We showed that FID-MRSI at a field strength of 9.4T is feasible. It was possible to reconstruct the missing FID points, so that the phase distortions present in the spectra could be reduced. Optimization of the water suppression scheme allowed significant reduction of total acquisition time. In conclusion, FID-MRSI at 9.4T is highly promising, as it addresses the most critical problems of chemical shift displacement and signal losses due to fast T2 relaxation.

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 Dates: 2015-03-19
 Publication Status: Published in print
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 Identifiers: URI: http://www.e-smi.eu/index.php?id=emim-2015-tubingen
BibTex Citekey: HochKBHSPES2015
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Title: 10th Annual Meeting of the European Society for Molecular Imaging (EMIM 2015)
Place of Event: Tübingen, Germany
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Title: 10th Annual Meeting of the European Society for Molecular Imaging (EMIM 2015)
Source Genre: Proceedings
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Pages: - Volume / Issue: - Sequence Number: 359 Start / End Page: - Identifier: -