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The use of a priori knowledge to quantify short echo in vivo 1 h mr spectra
Author(s) -
Stanley Jeff A.,
Drost Dick J.,
Williamson Peter C.,
Terry Thompson R.
Publication year - 1995
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910340105
Subject(s) - in vivo , phosphocreatine , nuclear magnetic resonance , creatine , metabolite , chemistry , choline , spectral line , physics , biology , biochemistry , endocrinology , microbiology and biotechnology , astronomy , energy metabolism
Abstract In vivo 1 H MR spectra of the prefrontal cortex acquired with the stimulated echo acquisition mode (STEAM) TE = 20 ms sequence were quantified to determine relative levels of cerebral metabolites. A priori knowledge of spectra from individual metabolites in aqueous solution was incorporated into a frequency domain quantification technique. The accuracy and precision of modeling these metabolites were investigated with simulated spectra of varying signal‐to‐noise ratios (SNRs) and relative metabolite levels. The efficacy of modeling in vivo data was tested by quantifying 10 repeated measures of two consecutively acquired in vivo spectra (an 8−cm 3 volume of interest (VOI) and a 4−cm 3 VOI positioned within the 8−cm 3 VOI) on the same normal subject. The differences in levels of glutamate (Glu), phosphocreatine plus creatine (PCr+Cr) and choline‐containing compounds (Cho 1 between spectra from the 8− and 4−cm 3 VOIs corresponded with the expected differences observed in the proportions of gray matter within the VOIs (estimated from 1 H images). Correcting for the T 1 and T 2 relaxation, the estimated concentrations of N ‐acetylaspartate, PCr+Cr, Cho 1 , Glu, and glutamine were consistent with previous in vivo and in vitro reports.