Single spin-echo T 2 relaxation times of cerebral metabolites at 14.1 T in the in vivo rat brain
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RESEARCH ARTICLE
Single spin-echo T2 relaxation times of cerebral metabolites at 14.1 T in the in vivo rat brain Lijing Xin • Giulio Gambarota • Cristina Cudalbu Vladimı´r Mlyna´rik • Rolf Gruetter
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Received: 14 January 2013 / Revised: 2 April 2013 / Accepted: 3 April 2013 / Published online: 21 April 2013 Ó ESMRMB 2013
Abstract Object To determine the single spin-echo T2 relaxation times of uncoupled and J-coupled metabolites in rat brain in vivo at 14.1 T and to compare these results with those previously obtained at 9.4 T. Materials and methods Measurements were performed on five rats at 14.1 T using the SPECIAL sequence and TEspecific basis-sets for LCModel analysis. Results and conclusion The T2 of singlets ranged from 98 to 148 ms and T2 of J-coupled metabolites ranged from 72 ms (glutamate) to 97 ms (myo-inositol). When comparing the T2s of the metabolites measured at 14.1 T with those previously measured at 9.4 T, a decreasing trend was found (p \ 0.0001). We conclude that the modest shortening of T2 at 14.1 T has a negligible impact on the L. Xin R. Gruetter Departments of Radiology, University of Lausanne, Lausanne, Switzerland L. Xin (&) Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), EPFL-SB-IPSB-LIFMET, Station 6, 1015 Lausanne, Switzerland e-mail: [email protected] G. Gambarota INSERM, U1099, 35000 Rennes, France G. Gambarota LTSI, Universite´ de Rennes 1, 35000 Rennes, France C. Cudalbu V. Mlyna´rik R. Gruetter Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fe´de´rale de Lausanne, Lausanne, Switzerland R. Gruetter Departments of Radiology, University of Geneva, Geneva, Switzerland
sensitivity of the 1H MRS when performed at TE shorter than 10 ms. Keywords T2 relaxation time Coupled spin systems Brain metabolites Proton magnetic resonance localized spectroscopy Abbreviations tCho Total choline (glycerophosphorylcholine ? phosphorylcholine) tCr Total creatine (phosphocreatine ? creatine) Cr Creatine GSH Glutathione Glu Glutamate Ins Myo-inositol NAA N-acetylaspartate Tau Taurine VOI Volume of interest SPECIAL SPin ECho, full Intensity Acquired Localized spectroscopy
Introduction In vivo 1H magnetic resonance spectroscopy (MRS) allows for noninvasive investigations of neurochemical information and thus has been widely used for studies of cerebral diseases such as Alzheimer’s disease, schizophrenia, stroke and others [1–3]. To preserve the maximum signal, a short TE is preferable for minimizing signal loss due to T2 relaxation and signal modulation due to J-coupling. As an alternative, a moderate/long TE is employed to eliminate the confounding macromolecule signal from the 1H MR spectra or to optimize the detection of specific metabolites of interest [4]. At a moderate/long TE, quantification of
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J-coupled cerebral metabolites is possible when taking into account the spectral shape modulation due to J-coupling, and the signal loss due to T2 relaxation time. The evaluation of the T2 relaxation time has been mostly performed for singlet resonances such
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