Single-voxel MR spectroscopy of gliomas with s-LASER at 7T

Abstract

Background and Purpose: Magnetic resonance spectroscopy (MRS) – a method to analyse metabolites in vivo – has been utilized in several studies of brain glioma biomarkers at lower fields strengths. At ultrahigh field strengths, MRS provides improved signal-to-noise-ratio and spectral resolution, but 7T studies on patients with gliomas are sparse. The purpose of this exploratory study was to evaluate the potential clinical implication of single-voxel MRS at 7T to assess metabolic information of lesions in a pilot cohort of patients with grade II and III gliomas. Methods: We scanned seven patients and seven healthy controls using the semi-localization by adiabatic-selective refocusing sequence on a Philips Achieva 7T system with a standard dual-transmit head coil. The metabolic ratios were calculated relative to water and total creatine. Additionally, 2-hydroxyglutarate (2-HG) MRS was carried out in four of the patients and 2-HG concentration was calculated relative to water. Results: When comparing tumour data to control regions in both patients and healthy controls, we found that choline/creatine and myo-inositol/creatine was significantly increased and that N-acetylaspartate/creatine and the neurotransmitter glutamate/creatine was significantly decreased. N-acetylaspartate/water and glutamate/water were also significantly decreased. Lactate/water and lactate/creatine showed an increase, although not significant. GABA/water was significantly decreased, but GABA/creatine was not. MRS spectra showed the presence of 2-HG in three of the four patients studied. Three of the patients, including the MRS 2-HG negative one, were operated and all of them had the IDH mutation. Conclusion: Our findings were consistent with existing literature on 3T- and 7T-MRS.

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“…GABA/water ratio was significantly decreased, and MRS spectra confirmed the presence of 2-hydroxyglutarate in three out of four patients studied. Overall, the study, conducted at 7 T, yielded results consistent with existing literature on both 3T and 7T MRS in glioma research[ 48 ]. In a retrospective study of 84 glioma patients, the potential for preoperative identification of isocitrate dehydrogenase (IDH) mutation status in glioma was explored using a combination of convolutional neural network (CNN) and ultra-high-field 7T chemical exchange saturation transfer (CEST) imaging[ 49 ].…”

“…This proposed approach is advised until a resolution is achieved for the observed extracranial shifts in 7T MRI scans[ 47 ]. An exploratory study aimed to assess the potential clinical implications of single-voxel 7T MR spectroscopy (MRS) in patients with grades II and III gliomas[ 48 ]. Seven patients and seven HCs were scanned, and metabolic ratios were calculated relative to water and total creatine.…”

“…Seven patients and seven HCs were scanned, and metabolic ratios were calculated relative to water and total creatine. The results revealed significant increases in choline/creatine and myoinositol/creatine ratios, along with decreases in N-acetyl aspartate/creatine and glutamate/creatine ratios when comparing tumor data to control regions[ 48 ]. The N-acetyl aspartate/water and glutamate/water ratios also showed significant decreases.…”