Following the discovery of 2-hydroxyglutarate (2HG) production in gliomas with mutations in isocitrate dehydrogenase 1 and 2 ¹, the capability of in-vivo detection of this onco-metabolite by MRS has become a central interest in cancer research. Recent studies ^2,3 showed that optimized long-TE MRS may be advantageous over standard short-TE MRS for 2HG measurement at 3T. Here we aim to evaluate the performance of long-TE MRS for 2HG detection in Philips, Siemens and GE 3T scanners.Among the five non-exchangeable J-coupled proton resonances of 2HG, the C4-proton resonances at ~2.25 ppm give rise to the largest signal in most experimental situations. The dependence of this 2.25-ppm resonance on the subecho times of PRESS, TE1 and TE2, was examined with numerical density-matrix simulations that incorporated the slice-selective RF and gradient pulses which are readily available in Philips, Siemens, and GE clinical scanners (Fig. 1). In-vitro experiments were conducted on a phantom solution with 2HG and Gly at three sites. In-vivo experiments were performed in patients with IDH-mutated gliomas at multiple centers (9 sites). Spectra were analyzed with LCModel using calculated spectra of 20 metabolites.The slice-selective refocusing RF pulse envelopes of the PRESS sequences in Philips, Siemens and GE 3T scanners were quite different, as shown in Fig. 1. In the GE PRESS, the flip angle of the refocusing pulse was set at 137° to improve the frequency profile shape. Numerical simulations indicated that, in each of the Philips, Siemens and GE PRESS sequences, the 2HG signal at short TE (e.g., ≤ 30 ms) was large but it was broad and thus not very ideal for 2HG signal differentiation from neighboring resonances (spectra not shown). In all cases, the 2HG signal varied extensively with changing TE₁ and TE₂, showing asymmetric dependence on TE₁ and TE₂ (Fig. 2). When normalized to the signal at (TE₁, TE₂) = (12, 12) ms, the PRESS sequences of Philips, Siemens and GE had temporal maxima of 77%, 85% and 81% at (TE₁, TE₂) = (32, 65), (30, 71), and (22, 82) ms, respectively, ignoring T2 relaxation effects. In-vitro and in-vivo experiments were carried out using TE = 97 ms for the convenience of individual sites, whose subecho times were (TE₁, TE₂) = (32, 65), (17, 80), and (26, 71) ms for Philips, Siemens and GE, respectively. The 2HG signal agreed well between phantom experiment and volume-localized simulation (Fig. 3a,b). The 2HG 2.25-ppm signals were large and narrow, with the H3 and H3’ resonances attenuated. For comparison, spectra calculated with hard pulses (without volume localization) were very different from phantom spectra (Fig. 3c). Finally we tested the TE = 97 ms PRESS of the three vendors in patients with IDH-mutated gliomas. In each case, a signal was clearly discernible at 2.25 ppm (Fig. 4). The in-vivo spectra were well reproduced by LCModel fits, resulting in negligible residuals at ~2.25 ppm (Residuals-1). When 2HG was removed from the basis set however, unfit residuals were observed at ~2.25 ppm in all three spectra (Residuals-2), indicating that 2HG was detected with high selectivity. The 2HG CRLB was less than 10% in all cases.This study reports multi-site test of optimized long-TE approaches in the MR scanners of three major vendors for detection of 2HG. Results show that the MRS methods have the capability of providing 2HG measurement with good precision in all three vendors. Since the RF pulses used are readily available in the vendor-supplied protocols, the data acquisition methods are easily transferable to other sites. The PRESS subecho times used for experiments were slightly different than suggested by simulations. This may not be problematic since the 2HG signals do not differ substantially between the simulation-suggested and experimental subecho time sets. Use of a proper basis is rather critical for reliable spectral analysis, as evidenced in Fig. 3. A major pitfall of this study is that, due to inconsistency of experimental conditions for reference water signal acquisition, the 2HG concentration is presented relative to the choline level, which is substantially altered in tumors. Future study requires standardization of the reference signal acquisition that will provide 2HG estimates directly comparable between vendors and sites. Lastly, the long-TE 2HG MRS can be easily extended to multi-voxel imaging with minimal interferences from macromolecules and lipids.Data indicate that 2HG-optimized long-TE approaches perform well in the Philips, Siemens and GE MR systems, giving rise to narrowing of the 2HG 2.25-ppm multiplet and consequently conferring precise estimation of 2HG. The long-TE MRS methods may therefore have the great potential for non-invasive diagnosis/prognosis in IDH-mutated gliomas.