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¹H MR Spectroscopy of the Brain: Absolute Quantification of Metabolites¹

¹ From the Department of Radiology, Maastricht University Hospital, P. Debyelaan 25, 6202 AZ Maastricht, the Netherlands; and Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands. Address correspondence to J.F.A.J. (e-mail: j.f.a.jansen{at}tue.nl).

View larger version (75K): [in a new window]   Figure 1: Schematic illustrates experimental setup of calibration strategies used for quantification of cerebral metabolite concentrations. Left: Setup for brain examination. Right: Calibration measurement. A, Internal endogenous marker, water signal reference method, and principle of reciprocity. B, External reference method. C, Replace-and-match method.

View larger version (49K): [in a new window]   Figure 2: 1H MR spectrum analyzed with LCModel (version 6.1-4) output of point-resolved spatially localized spectroscopy in a healthy adult subject. Spectra were recorded at 1.5 T (Intera; Philips Medical Systems, Best, the Netherlands) from the occipital lobe (repetition time msec/echo time msec, 2000/23; 128 signals acquired; voxel size, 8 cm3). In vivo spectrum (thin upper spectrum) was estimated with LCModel output (thick upper spectrum); the difference between spectra is plotted at the bottom. Above the difference spectrum is the baseline spline estimate, determined with LCModel. Inserted table at right displays estimated metabolite concentrations and Cramer-Rao minimum variance bounds. Cho = choline, Conc. = concentration, Cr = creatine, FWHM = full width at half maximum, Ins = myo-inositol, SD = standard deviation, tCr = total creatine.

View larger version (36K): [in a new window]   Figure 3: Fit results for point-resolved spatially localized 1H MR spectrum (3000/20; 128 signals acquired; voxel size, 16 cm3) obtained at 1.5 T (Signa; GE Healthcare, Milwaukee, Wis) from white matter in centrum semiovale of an 18-year-old control subject. Parameterized fitting with metabolite basis set fitting algorithm TDFDfit was used. At top are experimental spectrum, fitted spectrum, and residuals. Below are traces for the individual components that add up to the best fit (see reference 100 for definition of abbreviations). Some metabolites were split into two spectra, providing the freedom of differential T2 values for different protons in the same molecule. Baseline spectrum was obtained from a saturation recovery experiment. (Reprinted, with permission, from reference 100.)

View larger version (25K): [in a new window]   Figure 4: Point-resolved spatially localized 1H MR spectra obtained at 1.5 T (Signa, GE Healthcare) in a healthy adult. Spectra (6000/20; 128 signals acquired; voxel size, 12 cm3) were recorded from the centrum semiovale. A, Metabolites-of-interest (MOI) spectrum. B, Macromolecules-only (MM) spectrum. C, Sum spectra calculated from series of saturation-recovery spectra. Cho = choline, Ins = myo-inositol, tCr = total creatine. (Reprinted, with permission, from reference 97.)

View larger version (24K): [in a new window]   Figure 5: Water signal removal by means of Hankel-Lanczos singular-values decomposition filter. In vivo chemical shift imaging 1H MR spectroscopy in the brain of a healthy adult. A, Region indicated by horizontal bar contains the water peak. The peaks of interest, choline (Cho), total creatine (tCr), and NAA, are disturbed by right tail of the water peak. B, Spectrum after subtraction of water signal components, as retrieved and quantified with the Hankel-Lanczos singular-values decomposition filter in region of the horizontal bar in A. Components outside horizontal bar region are not affected by the procedure. (Reprinted, with permission, from reference 111.)