Short-echo three-dimensional H-1 MR spectroscopic imaging of patients with glioma at 7 tesla for characterization of differences in metabolite levels

Abstract

Purpose The purpose of this study was to evaluate the feasibility of using a short echo time, 3D H-1 magnetic resonance spectroscopic imaging (MRSI) sequence at 7T to assess the metabolic signature of lesions for patients with glioma. Materials and Methods 29 patients with glioma were studied. MRSI data were obtained using CHESS water suppression, spectrally-selective adiabatic inversion-recovery pulses and automatically prescribed outer-volume-suppression for lipid suppression, and spin echo slice selection (TE=30ms). An interleaved flyback echo-planar trajectory was applied to shorten the total acquisition time (~10min). Relative metabolite ratios were estimated in tumor and in normal-appearing white and gray matter (NAWM, GM). Results Levels of glutamine, myo-inositol, glycine and glutathione relative to total creatine (tCr) were significantly increased in the T2 lesions for all tumor grades compared to those in the NAWM (p < 0.05), while N-acetyl aspartate to tCr were significantly decreased (p < 0.05). In grade 2 gliomas, level of total choline-containing-compounds to tCr was significantly increased (p = 0.0137), while glutamate to tCr was significantly reduced (p = 0.0012). Conclusion The improved sensitivity of MRSI and the increased number of metabolites that can be evaluated using 7T MR scanners is of interest for evaluating patients with glioma. This study has successfully demonstrated the application of a short-echo spin-echo MRSI sequence to detect characteristic differences in regions of tumor versus normal appearing brain.

Refined modelling of the short-T2signal component and ensuing detection of glutamate and glutamine in short-TE, localised,1H MR spectra of human glioma measured at 3 T

“…vivo analysis of glial tumour biopsies . The same effect has also been observed in vivo by infusion of 13 C‐labelled glucose into human brain tumours and by 1 H three‐dimensional chemical shift imaging of gliomas . In a previous study of a larger group of oligodendrogliomas and astrocytomas, it was found that Glx and, especially tCho, increase in tumours relative to contralateral white matter .…”

“…Thus, there will be a glycine contribution to the mI signal. However, its relative signal contribution in glioma is similar to that in healthy parietal white matter, especially in grade II glioma, which dominates our dataset .…”

Comparison between Short and Long Echo Time Magnetic Resonance Spectroscopic Imaging at 3T and 7T for Evaluating Brain Metabolites in Patients with Glioma

“…The median automatically prescribed PRESS volume was 1032.4 cm 3 (range, 821.2–1244.5 cm 3 ) with an average of 6.7 cm in the S/I direction at 3T, while the excited slab at 7T was localized using spin echo slice selection with a fixed thickness of 4 cm. 16 Considering the location and width of the OVS bands, the percentage of excitation for each voxel was calculated. The median number of voxels that were excited was 523 (range, 465–765) and 405 (range, 282–542) at 3T and 7T, respectively.…”

“…The 7T MRSI data set had relatively less coverage because of the smaller number of phase encodes in the slice direction, which allowed for the application of an interleaved flyback trajectory and provided a bandwidth of 1916 Hz with a spectral resolution of ∼1.74 Hz per point. 16 The spatial resolution of 3D MRSI (1 cm 3 ) and the use of OVS bands meant that the number of voxels in the T2 lesion was smaller than the volume of T2 coverage, especially for tumors located close to skull.…”

Imaging Tumor Metabolism Using In Vivo Magnetic Resonance Spectroscopy

“…Figure 2B shows an example of in vivo 3D MRSI data at 7T from a patient with glioblastoma. The previous application of short echo time 3D MRSI in patients with glioma at 7T showed significantly increased levels of Cho, Gln, mI, Gly and GSH relatively to Cr and decreased NAA for regions of tumor versus normal brain [24]. The comparisons on reliability and practicality of using 7T relative to the more standard 3T scanner for assessing tumor would be important in planning the data acquisition for the cancer studies.…”