Spectroscopie proton du cerveau humain à 3T : Imagerie spectroscopique volumétrique spirale à TE court

Mohamed Tachrount 1
1 INSERM U836, équipe 5, Neuro-imagerie fonctionnelle et métabolique
GIN - U836 - Grenoble Institut des Neurosciences
Abstract : Proton MR chemical shift imaging (CSI) can identify biomarkers relevant to healthy or metabolic cerebral metabolism. At short TE, strongly J-coupled and short T2 metabolites can be detected. High field increases SNR and spectral resolution with the disadvantage of increased B1 and B0 heterogeneities as well as chemical shift displacement error (CSDE). Semi-LASER sequence reduces CSDE and B1 heterogeneity effects with improved slice selection profiles. Phase encoding CSI has long acquisition time. Spiral Spectroscopic Imaging (SSI) reduces minimum acquisition time. It becomes possible to acquire additional data such as a spatial dimension and/or a second spectral dimension. We developed a volumetric SSI of the human brain with a 17ms TE using PRESS with conventional RF pulses and with 32ms TE using semi-LASER combined with adapted water suppression and OVS modules. We implemented the trajectory measurement and 2D spatial - 1D spectral reconstruction programs. We observed good saturation of subcutaneous lipids. We obtained sharper selection profiles and reduced CSDE with adiabatic than conventional RF pulses. Using the measured trajectory for data reconstruction suppressed gradient hardware imperfections artefacts. With PRESS and semi-LASER selection modules, NAA, Cr, Cho, and myo-Inositol were significantly quantified. We have demonstrated in vivo short TE volumetric SSI acquisition at 3T using conventional and adiabatic refocusing pulses in a total acquisition time compatible with clinical examination. Further works need to be realised to optimise semi-LASER sequence for the detection of strongly coupled metabolite like glutamate and glutamine.
Document type :
Theses
Bioengineering. Université Joseph-Fourier - Grenoble I, 2009. French


https://tel.archives-ouvertes.fr/tel-00588326
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Submitted on : Friday, April 22, 2011 - 8:02:07 PM
Last modification on : Wednesday, October 29, 2014 - 1:24:08 PM

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Mohamed Tachrount. Spectroscopie proton du cerveau humain à 3T : Imagerie spectroscopique volumétrique spirale à TE court. Bioengineering. Université Joseph-Fourier - Grenoble I, 2009. French. <tel-00588326>

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