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Abstract:
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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 . |