Fast mapping of the T2 relaxation time of cerebral metabolites using proton echo-planar spectroscopic imaging (PEPSI)
Journal
Magnetic Resonance in Medicine
Journal Volume
57
Journal Issue
5
Pages
859-865
Date Issued
2007
Author(s)
Abstract
Metabolite T2 is necessary for accurate quantification of the absolute concentration of metabolites using long-echo-time (TE) acquisition schemes. However, lengthy data acquisition times pose a major challenge to mapping metabolite T2. In this study we used proton echo-planar spectroscopic imaging (PEPSI) at 3T to obtain fast T2 maps of three major cerebral metabolites: N-acetyl-aspartate (NAA), creatine (Cre), and choline (Cho). We showed that PEPSI spectra matched T2 values obtained using single-voxel spectroscopy (SVS). Data acquisition for 2D metabolite maps with a voxel volume of 0.95 ml (32 x 32 image matrix) can be completed in 25 min using five TEs and eight averages. A sufficient spectral signal-to-noise ratio (SNR) for T2 estimation was validated by high Pearson's correlation coefficients between logarithmic MR signals and TEs (R2 = 0.98, 0.97, and 0.95 for NAA, Cre, and Cho, respectively). In agreement with previous studies, we found that the T2 values of NAA, but not Cre and Cho, were significantly different between gray matter (GM) and white matter (WM; P < 0.001). The difference between the T2 estimates of the PEPSI and SVS scans was less than 9%. Consistent spatial distributions of T2 were found in six healthy subjects, and disagreement among subjects was less than 10%. In summary, the PEPSI technique is a robust method to obtain fast mapping of metabolite T2. ? 2007 Wiley-Liss, Inc.
Subjects
Cerebral metabolites; Gray/white matter difference; Proton echo-planar spectroscopic imaging; Single-voxel spectroscopy; T 2 relaxation time
SDGs
Other Subjects
Biomolecules; Correlation methods; Data acquisition; Mapping; Relaxation time; Signal to noise ratio; Accurate quantifications; Acquisition time; Cerebral metabolites; Echo-planar spectroscopic imaging; Gray/white matter difference; N-acetyl aspartate; Pearson's correlation coefficients; Single-voxel spectroscopies; Metabolites; choline; creatinine; n acetylaspartic acid; aspartic acid; choline; creatine; drug derivative; n acetylaspartic acid; N-acetylaspartate; proton; unclassified drug; adult; article; brain metabolism; correlation coefficient; echo planar imaging; female; gray matter; human; male; normal human; relaxation time; signal noise ratio; spectroscopy; white matter; brain; brain level; image processing; metabolism; methodology; nuclear magnetic resonance spectroscopy; Adult; Aspartic Acid; Brain; Brain Chemistry; Choline; Creatine; Echo-Planar Imaging; Female; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Spectroscopy; Male; Protons
Type
journal article