Magnetic Resonance Spectroscopy Study Of Metabolic Profiles In Brain Tumors
Patel, Aditya Manoj
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Metabolic profiles in brain tumors were measured using proton (1H) magnetic resonance spectroscopy (MRS) at 3T. Spectra were obtained from normal tissues and tumor mass regions of 6 low-grade gliomas, 7 anaplastic astrocytomas and 23 glioblastoma (GBM) patients, using PRESS at two echo times (TE = 54 and 112 ms). Glutamate (Glu), glutamine (Gln) and lactate (Lac) were well resolved at TE = 112 ms. The ratio of Gln and Glu concentrations, [Gln]/[Glu], was elevated significantly (p < 0.05) in all the tumor types compared to normal tissue. Elevation of Gln was confirmed through [Gln]/[water]; the ratio was increased in all the three tumor types but the increase was significant only in GBM. Glycine (Gly) was increased significantly in GBM. Alanine was detectable from GBM only, indicating its elevation for most malignant tumor. Other observations included significant increases in choline (Cho) and Lac (p < 0.05) and decrease in NAA (N-acetylaspartate), in consistent with prior studies. The creatine to water ratio was observed to decrease in tumor patients but was not significant. Myo-inositol (mIns) was observed to decrease in low grade patients as compared to normal tissue, but was seen to increase with grade of tumor, but was not significant. [Lac]/[water] was significantly higher and [Cho]/[Lac] significantly lower for GBM patients indicating the increase in Lac as compared to normal tissue.Treatment had a significant impact on tumor cells. After radiation therapy the Lac was observed to be elevated significantly and decrease after bevacizumab treatment. [Cho]/[Cr], [Cho]/[NAA], [Gln]/[Glu] and [Cho]/[Gly] was reduced significantly after the bevacizumab treatment. Gly was not detectable after Bevacizumab treatment. Some of the patients showed no infiltrating tumor cells after successful surgery and therapy with ratios close to that of normal tissue. These observations can help in characterizing the effect of various therapies on brain metabolites and tumor cells.