Quantitative ¹H‐MRS of healthy human cortex, hippocampus, and thalamus: Metabolite concentrations, quantification precision, and reproducibility

Abstract

Purpose:To evaluate metabolite concentrations in cortical gray matter, hippocampus, and thalamus of healthy adults, and to investigate precision and reproducibility of quantitative proton magnetic resonance spectroscopy ( 1 H-MRS) in these gray matter regions. Materials and Methods:Quantitative single-voxel short echo-time spectra were obtained from healthy human cortex, hippocampus, and thalamus. Subjects were examined twice. Metabolite concentrations, quantification precision, and reproducibility were determined.Results: There were no significant differences between test and retest measurements. Regional differences were observed with respect to metabolite concentrations, quantification precision, and reproducibility. Quantification precision and reproducibility of N-acetylaspartate and N-acetyl aspartylglutamate (tNAA), creatine and phosphocreatine (tCr), choline-containing compounds (Cho), and myo-inositol (myo-Ins), were better than those of glutamate (Glu) and glutamine (Gln). Generally, precision and reproducibility were better in cortex than in hippocampus or thalamus. The quantification precision was shown to correlate both with reproducibility and spectral linewidth. Conclusion:The reliability of quantitative MRS depends on the metabolite concerned, its concentration, and on the brain area studied. Moreover, the quantification precision of a metabolite in a single spectrum appears to be a reliable measure for its reproducibility in a longitudinal study. MULTIPLE SCLEROSIS (MS)is classically regarded as a demyelinating neurologic disease with relative sparing of the axons (1-3). However, it has become more clear over the past few years that gray matter (axonal) damage is in fact a common feature in the pathophysiology of MS, occurring in late as well as in the earliest phases of the disease (2-5), possibly even partly independent from the demyelinating process (3-5). Postmortem studies have shown that only a subset of the total amount of cortical lesions that arise in the territory of the small cortical veins are seen on conventional magnetic resonance imaging (MRI) (6). Cortical/subcortical lesion load on MRI was shown to correlate with cognitive impairment (7,8). Moreover, several studies have reported changes in MS hippocampus and thalamus related to cognitive dysfunction (9 -11). Therefore, it is essential that the gray matter is studied in more detail both structurally and metabolically.Proton magnetic resonance spectroscopy ( 1 H-MRS) can be used to study metabolite concentrations in several neurologic disorders, including MS (12-21). Most MRS and MRS imaging (MRSI) studies in MS focus on white matter pathology, rather than on gray matter. However, changes in metabolite peaks in MS gray matter have been reported previously (15).Because longitudinal studies are important in MS research to follow disease progression, it is essential to study reproducibility of the technique. Previous reproducibility studies have shown that intrasubject variability of MRS can be high, depending on the quantifi-

Comprehensive processing, display and analysis for in vivo MR spectroscopic imaging

“…These preliminary images show striking regional differences of metabolite concentrations. Some of these variations include higher NAA and creatine in cerebral GM than in cerebral WM, decreased choline in occipital GM and increased creatine and choline in the cerebellum and increased choline in the thalamus, in general agreement with previous studies (29)(30)(31)(32)(33), but with much greater regional definition. Some localized intensity changes of choline in frontal brain regions remain owing to incorrect fitting, arising from imperfect water suppression in these regions; however, this will be addressed by improving the quality evaluation procedures and by removing outliers in the mean value determination.…”

Limits of a localized magnetic resonance spectroscopy assay for ex vivo myocardial triacylglycerol

“…Although a limit-based error analysis of the relaxation correction has been published [37], many studies report CV's based only on repeated acquisitions and do not include the uncertainty of the T 2 correction [5,8,9,12]. For species with comparatively long T 2 's, such as brain metabolites, the additional uncertainty is minor.…”

“…Localized magnetic resonance spectroscopy (LMRS), which uses gradient-enabled imaging systems, is increasingly used both in basic and clinical assays including qualitative and quantitative compositional, temperature, and pH measurements [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Kreiss [16] summarized the main aspects of LMRS, including spectral artifacts, systematic errors, and general criteria for ensuring spectral quality.…”

Magnetic Resonance Spectroscopy: An Objectives Technique for the Quantification of Prostate Cancer Pathologies

“…Clinicians and scientists who have a more intimate understanding of MRS utilize many methods for quantification of in vivo MR spectra [117,[307][308][309][310][311][312][313][314]. A relative calculation can be performed in which metabolite peaks of interest are integrated and are normalized to a metabolite that is assumed to be unchanged by the disease.…”