Objective: To explore the usefulness of multivoxel 3D proton MR spectroscopy ((1)H-MRS) in assessing the recurrent contrast-enhancing areas at the site of the previously treated gliomas.
Materials and methods: In 28 patients who had new contrast-enhancing lesions in the vicinity of the previously resected and irradiated high-grade glioma, 3D (1)H-MRS examinations were performed on a 3.0T MR scanner. Spectral data for N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) were analyzed in all patients. Receiver operating characteristic analysis was performed, and the threshold value for tumor differentiation was determined. Diagnosis of these lesions was assigned by means of histopathology and follow-up.
Results: Diagnostic-quality 3D (1)H-MRS with quantifiable Cho, Cr, and NAA peaks was obtained in 92.9% of the cases. The Cho/NAA and Cho/Cr ratios were significantly higher in recurrent tumor than in radiation injury (P < 0.01), whereas the NAA/Cr ratios were lower in recurrent tumor than in radiation injury (P = 0.02). The Cho/Cr and Cho/NAA ratios were significantly higher in radiation injury than in normal-appearing white matter (P < 0.01), however, the NAA/Cr ratios were lower in radiation injury than in normal-appearing white matter (P = 0.01). Using receiver operating characteristic analysis, the resulting sensitivity, specificity and diagnostic accuracy of 3D (1)H-MRS were 94.1%, 100%, and 96.2%, respectively, based on the cut-off values of 1.71 for Cho/Cr or 1.71 for Cho/NAA or both as tumor criterion.
Conclusion: 3D (1)H-MRS could differentiate recurrent tumor from radiation injury in patients with recurrent contrast-enhancing lesions in the vicinity of the previously treated gliomas.