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Selective maximization of 31 P MR spectroscopic signals of in vivo human brain metabolites at 3T
Author(s) -
Blenman RoseAnn M.,
Port John D.,
Felmlee Joel P.
Publication year - 2007
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.20834
Subject(s) - sinc function , in vivo , metabolite , flip angle , pulse (music) , nuclear magnetic resonance , human brain , signal (programming language) , imaging phantom , echo time , pulse sequence , chemistry , nuclear medicine , materials science , magnetic resonance imaging , physics , medicine , optics , biology , biochemistry , computer science , microbiology and biotechnology , radiology , psychiatry , detector , computer vision , programming language
Purpose To develop a short TR, short TE, large flip angle (LFA), in vivo 31 P MR spectroscopy (MRS) technique at 3T that selectively maximizes the signal‐to‐noise ratio (SNR) of long T 1 human brain metabolites implicated in bipolar disorder. Materials and Methods Two pulse sequences were evaluated for efficiency. Slice profiles acquired with the scaled, sinc‐shaped, radiofrequency (RF) LFA pulses were compared to those acquired with Shinnar‐Le Roux (SLR) RF LFA pulses. The SLR‐based LFA pulse sequence was used to maximize the inorganic phosphate signal in a phantom, after which volunteer metabolite signals were selectively maximized and compared to their correlates acquired with conventional spin‐echo methods. Results The comparison of slice profiles acquired with sinc‐shaped RF LFA pulses vs. SLR RF LFA pulses showed that SLR‐based pulse sequences, with their improved excitation and slice profiles, yield significantly better results. In vivo LFA spin‐echo MRS implemented with SLR pulses selectively increased the 31 P MRS signal, by as much as 93%, of human brain metabolites that have T 1 times longer than the TR of the acquisition. Conclusion The data show that the LFA technique can be employed in vivo to maximize the signal of long T 1 31 P brain metabolites at a given TE and TR. LFAs ranging between 120° and 150° are shown to maximize the 31 P signal of human brain metabolites at 3T. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.