P-31 MR spectroscopy of normal human brain and brain tumors.

Abstract

Image-guided phosphorus-31 magnetic resonance (MR)-localized image-selected in vivo spectroscopy was performed on normal human brain and brain tumors. Peak area ratios, absolute molar concentrations of metabolites, and pH were determined. T1 values in normal brain were measured. The most important finding was that the metabolite concentrations detectable with MR spectroscopy in brain tumors were reduced from 20% to 70%. Phosphomonoesters, phosphodiesters, and phosphocreatine (PCr) showed the greatest decreases, while inorganic phosphate (Pi) showed the least change. The PCr-Pi ratio was significantly reduced in tumors. The pH of brain tumors (7.12 +/- 0.03) was more alkaline than that of normal brain (6.99 +/- 0.01). The authors conclude that the metabolite concentrations and pH in human brain tumors differ significantly from those in normal brain. These differences may be ultimately useful in characterizing tumors in man.

Selective maximization of 31P MR spectroscopic signals of in vivo human brain metabolites at 3T

“…However, the Cramer-Rao lower bounds, which actually reach a minimum at the optimal flip angle necessary to maximize each metabolite peak, suggest that the ability to estimate the spectral peak area and gain was not adversely affected by flip angle error resulting from increasing RF power. Instead, this observation of data spread as flip angle increased, as observed with the PCr peak, could be better explained by the Ϯ20% variability in volunteer T 1 relaxation times observed in multiple in vivo studies (5)(6)(7). Such T 1 variability would cause the differential response observed; at the 2s-TR used, larger gains would occur for those volunteers with longer PCr T 1 relaxation times, with maximal gain at larger optimal flip angles.…”

Use of 1H and 31P HRMAS to evaluate the relationship between quantitative alterations in metabolite concentrations and tissue features in human brain tumour biopsies

“…2D 1 H -1 H homonuclear or 1 H - 13 C heteronuclear experiments have improved the assignments in HRMAS spectra [3][4][5]8] but the quantitative metabolic information comes mainly from the 1 H 1D spectra. The use of 31 P NMR spectroscopy has also been demonstrated to be useful in the metabolomic study of brain cancer since there are 31 P-containing metabolites that can provide valuable information complementary to 1 H NMR in metabolic studies [9][10][11].…”

“…In this context, 31 P NMR spectra can inform about typical membrane components as the phosphomonoesters (PME) phosphoethanolamine (PE) and phospocholine (PC), mobile phosphodiesters (PDE) as glycerophosphorylethanolamine (GPE) and glycerophosphocholine (GPC) and less mobile phospholipids, as well as important energetic metabolism intermediates as phosphocreatine (PCr) and nucleotides-phosphate [9,10,12]. Moreover, the pH can be inferred from the changes in the chemical shift of some 31 P-metabolites [9,10,13].…”

“…Moreover, the pH can be inferred from the changes in the chemical shift of some 31 P-metabolites [9,10,13]. In vivo, the pH is usually determined using the chemical shift of…”

“…Pi signal relative to PCr, whose chemical shift is pH-independent in the physiologic range of pH [9,14].…”