Optimization of spectrally selective 180° radiofrequency pulse timings in J-difference editing (MEGA) of lactate.

Purpose: J-Difference editing (MEGA) provides an effective spectroscopic means of selectively measuring low-concentration metabolites having weakly coupled spins. The fractional inphase and antiphase coherences are determined by the radiofrequency (RF) pulses and inter-RF pulse intervals of the sequence. We examined the timings of the spectrally selective editing 180° pulses (E180) in MEGA-PRESS to maximize the edited signal amplitude in lactate at 3T.

Glycine by MR spectroscopy is an imaging biomarker of glioma aggressiveness.

Background: High-grade gliomas likely remodel the metabolic machinery to meet the increased demands for amino acids and nucleotides during rapid cell proliferation. Glycine, a non-essential amino acid and intermediate of nucleotide biosynthesis, may increase with proliferation. Non-invasive measurement of glycine by magnetic resonance spectroscopy (MRS) was evaluated as an imaging biomarker for assessment of tumor aggressiveness.

In vivo MRS measurement of 2-hydroxyglutarate in patient-derived IDH-mutant xenograft mouse models versus glioma patients.

Purpose: To generate a preclinical model of isocitrate dehydrogenase (IDH) mutant gliomas from glioma patients and design a MRS method to test the compatibility of 2-hydroxyglutarate (2HG) production between the preclinical model and patients.

Methods: Five patient-derived xenograft (PDX) mice were generated from two glioma patients with IDH1 R132H mutation. A PRESS sequence was tailored at 9.

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

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.

Distinction of the GABA 2.29 ppm resonance using triple refocusing at 3 T in vivo.

Purpose: To develop H MR spectroscopy that provides distinction of γ-aminobutyric acid (GABA) signal at 3 T in vivo.

Methods: Triple-refocusing was tailored at 3 T, with numerical simulations and phantom validation, for distinction of the GABA 2.29-ppm resonance from the neighboring glutamate resonance.

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

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.

Measurement of glycine in healthy and tumorous brain by triple-refocusing MRS at 3 T in vivo.

Glycine (Gly) has been implicated in several neurological disorders, including malignant brain tumors. The precise measurement of Gly is challenging largely as a result of the spectral overlap with myo-inositol (mI). We report a new triple-refocusing sequence for the reliable co-detection of Gly and mI at 3 T and for the evaluation of Gly in healthy and tumorous brain.

Prospective Longitudinal Analysis of 2-Hydroxyglutarate Magnetic Resonance Spectroscopy Identifies Broad Clinical Utility for the Management of Patients With IDH-Mutant Glioma.

Purpose Proton magnetic resonance spectroscopy (MRS) of the brain can detect 2-hydroxyglutarate (2HG), the oncometabolite produced in neoplasms harboring a mutation in the gene coding for isocitrate dehydrogenase ( IDH). We conducted a prospective longitudinal imaging study to determine whether quantitative assessment of 2HG by MRS could serve as a noninvasive clinical imaging biomarker for IDH-mutated gliomas. Patients and Methods 2HG MRS was performed in 136 patients using point-resolved spectroscopy at 3 T in parallel with standard clinical magnetic resonance imaging and assessment.

Detection of 2-hydroxyglutarate in brain tumors by triple-refocusing MR spectroscopy at 3T in vivo.

Purpose: To test the efficacy of triple-refocusing MR spectroscopy (MRS) for improved detection of 2-hydroxyglutarate (2HG) in brain tumors at 3T in vivo.

Methods: The triple-refocusing sequence parameters were tailored at 3T, with density-matrix simulations and phantom validation, for enhancing the 2HG 2.25-ppm signal selectivity with respect to the adjacent resonances of glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA).

In vivo detection of 2-hydroxyglutarate in brain tumors by optimized point-resolved spectroscopy (PRESS) at 7T.

Purpose: To test the efficacy of 7T MRS for in vivo detection of 2-hydroxyglutarate (2HG) in brain tumors.

Methods: The subecho times of point-resolved spectroscopy (PRESS) were optimized at 7T with density-matrix simulations and phantom validation to improve the 2HG signal selectivity with respect to the neighboring resonances of γ-aminobutyric acid (GABA), glutamate (Glu), and glutamine (Gln). MRS data were acquired from 12 subjects with gliomas in vivo and analyzed with LCModel using calculated basis spectra.

Measurement of regional variation of GABA in the human brain by optimized point-resolved spectroscopy at 7 T in vivo.

The (1)H resonances of γ-aminobutyric acid (GABA) in the human brain in vivo are extensively overlapped with the neighboring abundant resonances of other metabolites and remain indiscernible in short-TE MRS at 7 T. Here we report that the GABA resonance at 2.28 ppm can be fully resolved by means of echo time optimization of a point-resolved spectroscopy (PRESS) scheme.

Proton T2 measurement and quantification of lactate in brain tumors by MRS at 3 Tesla in vivo.

Purpose: To evaluate the T2 relaxation time of lactate (Lac) in brain tumors and the correlation of the T2 and concentration with tumor grades.

Methods: Eight pairs of the subecho time sets of point-resolved spectroscopy were selected between 58 and 268 ms, with numerical and phantom analyses, for Lac T2 measurement. In vivo spectra were acquired from 24 subjects with gliomas (13 low grade and 11 high grade) and analyzed with LCModel using numerically-calculated basis spectra.

In vivo detection of citrate in brain tumors by 1H magnetic resonance spectroscopy at 3T.

Purpose: To test whether citrate is elevated in adult patients with gliomas using (1)H magnetic resonance spectroscopy (MRS) at 3T in vivo.

Methods: Thirty-four adult patients were enrolled in the study, including six subjects with glioblastomas, eight subjects with astrocytomas (World Health Organization grade 3, n = 5; grade 2, n = 3), and 20 subjects with oligodendrogliomas (grade 3, n = 5; grade 2, n = 15). Five healthy volunteers were studied for baseline citrate data.