Direct absolute quantification of metabolites in the human brain with in vivo localized proton spectroscopy

Abstract

The absolute concentrations of the three major brain metabolites observable by in vivo proton spectroscopy--N-acetylaspartate(NAA), creatine and phosphocreatine (Cr and PCr) and choline (Cho)--have been measured at four standardized localizations in 34 healthy volunteers by in vivo localized proton spectroscopy using an external reference sample. The results show that the concentration of Cr and PCr as observed by in vivo MRS (5-6 mmol/L) is lower than that measured by other methods. The results are concordant with the hypothesis, that the Cr and PCr resonance as observed by proton spectroscopy is due mainly to PCr, whereas Cr remains invisible by being attached to a larger molecule. It is also demonstrated, that Cr and PCr is higher in the cerebellum than in the cerebrum, whereas NAA remains constant within the margin of error (8-9 mmol/L).

Reproducibility of Proton Magnetic Resonance Spectroscopic Imaging in Patients with Schizophrenia

“…These results are consistent with previous studies (Tedeschi et al 1995b;Frahm et al 1989;Hennig et al 1992), which have shown that CRE (which measures both phosphocreatine and creatine at equilibrium in cell energy metabolism) reveals the lowest variability among the metabolites studied by 1 H-MRS (Frahm et al 1989;Hennig et al 1992). Indeed, the two least variable ratios have CRE as the denominator.…”

Single‐voxel long TE 1H‐MR spectroscopy of the normal brainstem and cerebellum

“…These data are explained by the ranks of the concentrations we measured in the same locations but the medulla. In fact, in line with quantitative 1H-MRS studies using short and long TE sequences (14,17,18), our results indicate that the total NAA, including N-acetylspartate and N-acetylaspartylglutamate, is heterogeneously distributed throughout the brain, and that the highest concentration of Cr is located in the cerebellum, possibly related to the high creatine kinase activity (14,17). In line with Michaelis et al (18), we observed the highest Cho concentration in the pons.…”

Quantitative single‐voxel spectroscopy: The reciprocity principle for receive‐only head coils

“…Hennig et al (19) measured lower B1 inhomogeneities with signal variations of 3%, whereas Helms (15) has reported much higher B1 inhomogeneities (8 -16%). These inconsistent results indicate that the B1 inhomogeneities depend on type and quality of the RF coil.…”