Preoperative Grading of Gliomas by Using Metabolite Quantification with High-Spatial-Resolution Proton MR Spectroscopic Imaging1

doi:10.1148/radiol.2382041896

Preoperative Grading of Gliomas by Using Metabolite Quantification with High-Spatial-Resolution Proton MR Spectroscopic Imaging¹

¹From the Department of Neurosurgery, Neurocenter, University of Erlangen-Nuremberg, Erlangen, Germany. Received November 8, 2004; revision requested January 5, 2005; revision received February 11; accepted March 7; final version accepted April 5. A.S. supported by the German Research Society (DFG Ga 638/2-1). S.G. supported by the Austrian Science Fund (FWF P14715-PSY).

Address correspondence to
E.M., MR Center of Excellence, Medical University of Vienna, Lazarettgasse 14, A-1090 Vienna, Austria (e-mail: ewald.moser{at}meduniwien.ac.at).

Abstract

Purpose: To evaluate proton magnetic resonance (MR) spectroscopic imaging with high spatial resolution for preoperative grading of suspected World Health Organization grades II and III gliomas.

Materials and Methods: Institutional ethics committee approval and informed consent were obtained for control subjects but were not required for the retrospective component involving patients. Twenty-six patients (10 women, 16 men; mean age, 37.5 years) suspected of having gliomas and 26 age- and sex-matched control subjects underwent proton MR spectroscopy. Absolute metabolite concentrations for choline-containing compounds (Cho), creatine (Cr), and N-acetylaspartate (NAA)–N-acetylaspartylglutamate (total NAA [tNAA]) were calculated by using a user-independent spectral fit program. Metabolic maps of Cho/tNAA ratios were calculated, segmented, and used for MR spectroszpcopy–guided stereotactic brain biopsy. Two-sided paired Student t tests were used to test for statistical significance.

Results: Significantly lower Cho levels (P = .002) and higher tNAA levels (P = .010) were found in grade II tumors (n = 9) compared with grade III tumors (n = 17). The average Cho/tNAA ratio over the voxels in the tumor center showed a distinct difference (P < .001) between grade II and III gliomas at a threshold of 0.8 (with ratios <0.8 for grade II). The maximum Cr concentration in the tumor showed a clear-cut threshold between grade III oligodendrogliomas and oligoastrocytomas (Cr level, <7 mmol/L) and grade III astrocytomas (Cr level, >7 mmol/L; P = .020). Comparison between the histopathologic findings from the MR spectroscopy–guided biopsy samples (76 biopsies from 26 patients) and molar metabolite values in corresponding voxels located at the biopsy sampling points showed a negative linear correlation for tNAA (r = −0.905) and a positive exponential correlation for Cho (r = 0.769) and Cho/tNAA (r = 0.885).

Conclusion: Proton MR spectroscopic imaging with high spatial resolution allows preoperative grading of gliomas.

Cho = choline-containing compounds
Cr = creatine
FWHM = full width at half maximum
NAA = N-acetylaspartate
tNAA = total NAA

Footnotes

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, E.M., O.G.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, A.S., S.G., R.F., T.H., B.T., E.M., O.G.; clinical studies, C.N., O.G.; experimental studies, A.S., R.B., O.G.; statistical analysis, A.S.; and manuscript editing, A.S., S.G., C.N., R.F., T.H., B.T., E.M., O.G.
© RSNA, 2006