Echo-planar spectroscopic imaging with dual-readout alternated gradients (DRAG-EPSI) at 7 T: Application for 2-hydroxyglutarate imaging in glioma patients

Zhongxu An, Vivek Tiwari, Sandeep K. Ganji, Jeannie Baxter, Michael Levy, Marco C. Pinho, Edward Pan, Elizabeth A. Maher, Toral R. Patel, Bruce E. Mickey, Changho Choi

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Purpose: To develop echo-planar spectroscopic imaging (EPSI) with large spectral width and accomplish high-resolution imaging of 2-hydroxyglutarate (2HG) at 7 T. Methods: We designed a new EPSI readout scheme at 7 T. Data were recorded with dual-readout alternated gradients and combined according to the gradient polarity. Following validation of its performance in phantoms, the new readout scheme, together with previously reported 2HG-optimized magnetic resonance spectroscopy (point-resolved spectroscopy echo time of 78 ms), was used for time-efficient and high-resolution imaging of 2HG and other metabolites in five glioma patients before treatment. Unsuppressed water, acquired with EPSI, was used as reference for multichannel combination, eddy-current compensation, and metabolite quantification. Spectral fitting was conducted with the LCModel using in-house calculated basis sets. Results: Using a readout gradient strength of 9.5 mT/m and slew rate of 90 mT/m/ms, dual-readout alternated gradients EPSI permitted 1638-Hz spectral width with 6 × 6 mm2 in-plane resolution at 7 T. Phantom data indicated that dual-readout alternated gradients EPSI provides proper metabolite signals and induces much less frequency drifts than conventional EPSI. For a spatial resolution of 0.5 mL, 2HG was detected in tumors with precision (Cramer-Rao lower bound < 10%). The 2HG was estimated to be 2.3 to 3.3 mM in tumors of three patients with biopsy-proven isocitrate dehydrogenase (IDH) mutant gliomas. The 2HG was undetectable in an IDH wild-type glioblastoma. For a radiographically suggested glioma, the estimated 2HG of 2.3 ± 0.2 mM (Cramer-Rao lower bound < 10%) indicated that the lesion may be an IDH mutant glioma. Conclusions: The data indicated that the dual-readout alternated gradients EPSI can provide reliable high-resolution imaging of 2HG in glioma patients at 7 T in vivo. Magn Reson Med 79:1851–1861, 2018.

Original languageEnglish (US)
Pages (from-to)1851-1861
Number of pages11
JournalMagnetic resonance in medicine
Volume79
Issue number4
DOIs
StatePublished - Apr 2018

Keywords

  • 2-hydroxyglutarate (2HG)
  • 7T
  • H MRS
  • dual-readout alternated-gradients EPSI (DRAG-EPSI)
  • echo-planar spectroscopy imaging (EPSI)
  • glioma
  • human brain tumor

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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