3D high‐resolution imaging of 2‐hydroxyglutarate in glioma patients using DRAG‐EPSI at 3T in vivo

Abstract

Purpose To develop 3D high‐resolution imaging of 2‐hydroxyglutarate (2HG) at 3T in vivo. Methods Echo‐planar spectroscopic imaging with dual‐readout alternated‐gradients (DRAG‐EPSI), which was recently reported for 2D imaging of 2HG at 7T, was tested for 3D imaging of 2HG at 3T. The frequency drifts and acoustic noise induced by DRAG‐EPSI were investigated in comparison with conventional EPSI. Four patients with IDH‐mutant gliomas were enrolled for 3D imaging of 2HG and other metabolites. A previously reported 2HG‐tailored TE 97‐ms PRESS sequence preceded the DRAG‐EPSI readout gradients. Unsuppressed water, acquired with EPSI, was used as reference for multi‐channel combination, eddy‐current compensation, and metabolite quantification. Spectral fitting was conducted with the LCModel using in‐house basis sets. Results With gradient strength of 4 mT/m and slew rate of 20 mT/m/ms, DRAG‐EPSI produced frequency drifts smaller by 5.5‐fold and acoustic noise lower by 25 dB compared to conventional EPSI. In a 19‐min scan, 3D DRAG‐EPSI provided images of 2HG with precision (CRLB <10%) at a resolution of 10 × 10 × 10 mm 3 for a field of view of 240 × 180 × 80 mm 3 . 2HG was estimated to be 5 mM in a pre‐treatment patient. In 3 post‐surgery patients, 2HG estimates were 3–6 mM, and the 2HG distribution was different from the water‐T 2 image pattern or highly concentrated in the post‐contrast enhancing region. Conclusion Together with 2HG‐optimized PRESS, DRAG‐EPSI provides an effective tool for reliable 3D high‐resolution imaging of 2HG at 3T in vivo.