Comparison of T1 and T2 metabolite relaxation times in glioma and normal brain at 3T

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Abstract
Purpose: To measure T1 and T2 relaxation times of metabolites in glioma patients at 3T and to investigate how these values influence the observed metabolite levels.Materials and Methods: A total of 23 patients with gliomas and 10 volunteers were studied with single‐voxel two‐dimensional (2D) J‐resolved point‐resolved spectral selection (PRESS) using a 3T MR scanner. Voxels were chosen in normal appearing white matter (WM) and in regions of tumor. The T1 and T2 of choline containing compounds (Cho), creatine (Cr), and N‐acetyl aspartate (NAA) were estimated.Results: Metabolite T1 relaxation values in gliomas were not significantly different from values in normal WM. The T2 of Cho and Cr were statistically significantly longer for grade 4 gliomas than for normal WM but the T2 of NAA was similar. These differences were large enough to impact the corrections of metabolite levels for relaxation times with tumor grade in terms of metabolite ratios (P < 0.001).Conclusion: The differential increase in T2 for Cho and Cr relative to NAA means that the ratios of Cho/NAA and Cr/NAA are higher in tumor at longer echo times (TEs) relative to values in normal appearing brain. Having this information may be useful in defining the acquisition parameters for optimizing contrast between tumor and normal tissue in MR spectroscopic imaging (MRSI) data, in which limited time is available and only one TE can be used. J. Magn. Reson. Imaging 2008;28:342–350.

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