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Published on: May 31, 2020
Low-grade glioma: correlation of short echo time 1H-MR spectroscopy with 23Na MR imaging
R Bartha1, J F Megyesi, C J Watling
1Laboratory for Functional Magnetic Resonance Research, Robarts Research Institute, London, Ontario, Canada. rob.bartha@imaging.robarts.ca
Background And Purpose:
There is considerable variability in the clinical behavior and treatment response of low-grade (WHO grade II) gliomas. The purpose of this work was to characterize the metabolic profile of low-grade gliomas by using short echo time (1)H-MR spectroscopy and to correlate metabolite levels with MR imaging-measured sodium ((23)Na) signal intensity. Based on previous studies, we hypothesized decreased N-acetylaspartate (NAA) and increased myo-inositol (mIns), choline (Cho), glutamate (Glu), and (23)Na signal intensity in glioma tissue.
Materials And Methods:
Institutional ethics committee approval and informed consent were obtained for all of the subjects. Proton ((1)H-MR) spectroscopy (TR/TE = 2200/46 ms) and sodium ((23)Na) MR imaging were performed at 4T in 13 subjects (6 women and 7 men; mean age, 44 years) with suspected low-grade glioma. Absolute metabolite levels were quantified, and relative (23)Na levels were measured in low-grade glioma and compared with the contralateral side in the same patients. Two-sided Student t tests were used to test for statistical significance.
Results:
Significant decreases were observed for NAA (P < .001) and Glu (P = .004), and increases were observed for mIns (P = .003), Cho (P = .025), and sodium signal intensity (P < .001) in low-grade glioma tissue. Significant correlations (r(2) > 0.25) were observed between NAA and Glu (P < .05) and between NAA and mIns (P < .01). Significant correlations were also observed between (23)Na signal intensity and NAA (P < .01) and between (23)Na signal intensity and Glu (P < .01). Ratios of NAA/mIns, NAA/(23)Na, and NAA/Cho were altered in glioma tissue (P < .001); however based on the t statistic, NAA/(23)Na (t = 9.6) was the most significant, followed by NAA/mIns (t = 6.1), and NAA/Cho (t = 5.0).
Conclusion:
Although Glu concentration is reduced and mIns concentration is elevated in low-grade glioma tissue, the NAA/(23)Na ratio was the most sensitive indicator of pathologic tissue.
