Quantification of cerebral metabolites in glioma patients with proton MR spectroscopy using T2 relaxation time correction

Low-Grade Glioma: Correlation of Short Echo Time1H-MR Spectroscopy with23Na MR Imaging

“…Because the same method could not be used to determine the contribution of glioma tissue to a voxel, an average ratio of glioma tissue/CSF within a voxel was estimated as 98%/2% in low-grade tumors. A correction was made for T1 and T2 relaxation signal intensity loss in water and metabolite spectra by using estimates of these time constants from the literature 6,19,[30][31][32][33] (Table). For spectra acquired in tissue contralateral to the tumor, a weighted average of relaxation time constants based on the average gray matter/white matter tissue fraction was used to determine T1 and T2 signal intensity attenuation.…”

“…The measurement of metabolite T2 values in tumors has been only sparsely reported, with considerable variability for NAA, Cr, and Cho. 6,[34][35][36] Due to the inconsistency in these reports, the values for normal white matter were used in the current study. The average line width (full width at half maximum) of the unsuppressed water spectra was quantified for tumors and control data to support the use of a greater T2 time constant in glioma tissue.…”

“…Metabolic profiling of these tumors with MR spectroscopy has the potential to improve our ability to predict the biological behavior and treatment response of low-grade gliomas and to better delineate tumor boundaries. Previous in vitro and in vivo MR spectroscopy studies have identified metabolic markers that help noninvasively discriminate tumor type, [6][7][8] aid in radiation treatment planning, 9 or predict survival. 10 Most studies have used long echotime spectroscopy acquisitions (TE Ն 130 ms), limiting tumor metabolite characterization to the dominant peaks in the 1 H spectrum: N-acetylaspartate (NAA; a putative marker of neuronal viability), total creatine (Cr; involved in energy metabolism), choline-containing compounds (Cho; associated with membrane breakdown/synthesis), and lactate (associated with anaerobic glycolysis).…”

“…Typically, low-grade glioma is characterized by reduced NAA due to reduced neuronal attenuation, reduced Cr due to a hypermetabolic state, and increased Cho, reflecting increased membrane turnover. 6,8 The metabolites glutamate (Glu) and myo-inositol (mIns), measurable by shorter echotime 1 H-MR spectroscopy, may provide additional information about the pathologic state of the neoplasm. A previous study 11 has demonstrated that highly malignant tumors may release excess Glu to kill surrounding tissue and promote tumor growth, and increased Glu plus glutamine (Gln) has been measured previously in oligodendroglioma by 1 H-MR spectroscopy.…”

Choline-containing compounds quantification by 1H NMR spectroscopy using external reference and noise measurements

“…This can be achieved using correction factors, but they require knowledge of T 1 and T 2 relaxation times in tissues. When performing acquisitions at short echo times, T 2 effects cause small corrections, about 3%, that can be ignored to avoid time consuming determination of T 2 values [42,43]. Evaluation of T 1 relaxation times is often impractical in a clinical setting, due to the excessive examination time needed to measure it and its minor contribution to data quantification [42].…”