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The use of a priori knowledge to quantify short echo in vivo1h mr spectra

✍ Scribed by Jeff A. Stanley; Dick J. Drost; Peter C. Williamson; R. Terry Thompson

Publisher
John Wiley and Sons
Year
1995
Tongue
English
Weight
805 KB
Volume
34
Category
Article
ISSN
0740-3194

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✦ Synopsis

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.

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