Purpose: To investigate the TE dependence of the edited 2-hydroxyglutarate (2HG) signal, its separation from co-edited glutamate plus glutamine (Glx), and fit accuracy in the presence of nuisance signals using a MEGA-PRESS sequence.
Methods: Simulations were performed at TEs 70-160 ms to assess the signal intensity and 2HG-Glx overlap as a function of TE. The effect of the 2HG-Glx spectral overlap on the fit accuracy of 2HG was evaluated on simulated 2HG-edited spectra with in vivo parameter variations. Data were acquired at TEs of 70 and 90 ms in 13 glioma patients to estimate the TE-dependence of the 2HG and Glx signal intensity and at a TE of 120 ms in eight glioma patients to estimate the in vivo 2HG, Glx, and water T2 relaxation times.
Results: A TE of 90 ms was found to produce a maximal 2HG integral, which was 23% larger than that at a TE of 70 ms in vivo without a significant increase in 2HG-Glx overlap. Lipid and residual water were 26% and 16% lower, respectively, at a TE of 90 ms versus 70 ms. Fit-quality numbers were 49% lower at a TE of 90 ms versus 70 ms, indicating enhanced fits at a TE of 90 ms. The in vivo T2 relaxation times of 2HG, Glx, and water were 264, 177, and 110 ms, respectively.
Conclusion: A TE of 90 ms was best with a maximal 2HG signal, minimal 2HG-Glx overlap, and minimal residual water and lipid contamination.
Keywords: 2HG; J‐difference editing; MR spectroscopy; glioma; tumor.
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