Differentiation of high-grade and low-grade gliomas using pattern analysis of long-echo single-voxel proton magnetic resonance spectroscopy ( ¹H-MRS)

The usefulness of proton magnetic resonance spectroscopy ( ¹H-MRS) for glioma grading is not clear, particularly due to the absence of standard criteria for data analysis. Previously we had developed an original classification of the pathological ¹H-MR spectra based on the identification of the predominant metabolite peak, N-acetylaspartate (NAA)for Type I, choline-containing compounds (Cho) for Type II, and mobile lipids (Lip) for Type III, and presence or absence of other metabolite peaks: lactate (Lac), Lip, or Cho. The present study evaluated the effectiveness of this classification in grading of previously non-treated gliomas. A total of 38 low-grade and 33 high-grade neoplasms were investigated. Four tumors had ¹H-MR spectra Type I, and all of those were low-grade. Three tumors had ¹H-MR spectra Type III, and all those were glioblastomas. Fifteen tumors with ¹H-MR spectra Type II had a Lip/NAA ratio more than 1 (Type II C with moderate elevation of lipids), and 12 of those neoplasms were high-grade. The differences in distribution of high-grade and low-grade gliomas among another 49 gliomas with ¹H-MR spectra Type II did not depend on the presence of Lac and/or Lip peaks, and in this subgroup NAA/Cho ratio was also evaluated. Inclusion of both characteristics (type of the ¹H-MR spectrum and NAA/Cho ratio with defined cut-off level of 0.6) into the diagnostic algorithm yielded 72% diagnostic accuracy (95% confidence interval: 62%-82%) in discriminating high-grade and low-grade neoplasms. In conclusion, pattern analysis of the pathological ¹H-MR spectra using the proposed classification along with evaluation of NAA/Cho ratio might be helpful for non-invasive glioma grading.