Regional Metabolite Concentrations in Aging Human Brain: Comparison of Short-TE Whole Brain MR Spectroscopic Imaging and Single Voxel Spectroscopy at 3T

Abstract

Purpose: The aim of this study was to compare a recently established whole brain MR spectroscopic imaging (wbMRSI) technique using spin-echo planar spectroscopic imaging (EPSI) acquisition and the Metabolic Imaging and Data Analysis System (MIDAS) software package with single voxel spectroscopy (SVS) technique and LCModel analysis for determination of relative metabolite concentrations in aging human brain.

Methods: A total of 59 healthy subjects aged 20-70 years (n ≥ 5 per age decade for each gender) underwent a wbEPSI scan and 3 SVS scans of a 4 ml voxel volume located in the right basal ganglia, occipital grey matter and parietal white matter. Concentration ratios to total creatine (tCr) for N‑acetylaspartate (NAA/tCr), total choline (tCho/tCr), glutamine (Gln/tCr), glutamate (Glu/tCr) and myoinositol (mI/tCr) were obtained both from EPSI and SVS acquisitions with either LCModel or MIDAS. In addition, an aqueous phantom containing known metabolite concentrations was also measured.

Results: Metabolite concentrations obtained with wbMRSI and SVS were comparable and consistent with those reported previously. Decreases of NAA/tCr and increases of line width with age were found with both techniques, while the results obtained from EPSI acquisition revealed generally narrower line widths and smaller Cramer-Rao lower bounds than those from SVS data.

Conclusion: The wbMRSI could be used to estimate metabolites in vivo and in vitro with the same reliability as using SVS, with the main advantage being the ability to determine metabolite concentrations in multiple brain structure simultaneously in vivo. It is expected to be widely used in clinical diagnostics and neuroscience.

Keywords: Aging; Metabolic Imaging and Data Analysis System; Spin-echo planar spectroscopic imaging.

Fig. 1

MR spectra and the regions of interest (ROIs) used, shown on the T1-weighted image of the aqueous phantom. a The spectrum of a single voxel spectroscopy (SVS) acquisition and the LCModel fit curve of the ROI are shown as empty squares (SVS-LCM method). b The integrated spectrum from the whole brain MR spectroscopic imaging (wbMRSI) data from the same ROI volume used for the SVS voxel (wbMRSI). c The integrated spectrum and the LCModel fit (hybrid)

Fig. 2

Locations of the ROIs in basal ganglia (BG), parietal white matter (pWM) and occipital grey matter (oGM) drawn on T1-weighted images in axial (2nd and 3rd rows), sagittal (upper row), and coronar (lower row) sections, shown for a the SVS acquisition and b the integrated wbMRSI measurement

Fig. 3

Spectra and fit results for SVS scans with the LCModel fit (first row), wbMRSI measurements (second row) and wbMRSI measurements with LCModel fit (third row). Data are shown for parietal white matter (column a), occipital grey matter (column b) and basal ganglia (column c)

Fig. 4

Regional metabolite concentrations of NAA/tCr, tCho/tCr, Gln/tCr, Glu/tCr, and MI/tCr, and spectral line widths at each ROI plotted against age, which were measured with SVS and analyzed with the LCModel (indicated as SVS-LCM), wbMRSI and analyzed with MIDAS (indicated as wbMRSI), and wbMRSI and analyzed with LCModel (indicated as hybrid)