Article
Choline containing compounds in the discrimination between high- and low-grade gliomas – comparison of maximum and mean values
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Published: | May 20, 2009 |
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Objective: In addition to standard MR-protocols, MR-spectroscopy is increasingly used in the characterization of brain tumors, while usually different metabolite ratios are calculated. However, there are great inter-individual and intra-individual differences in many metabolite values, so comparison is problematical. In this study, we sought to assess normalized mean and maximum choline (Cho) values as single parameters in the non-invasive grading of gliomas.
Methods: 1H-spectroscopic imaging data of 63 patients with suspected non-necrotic WHO °II or °III gliomas were acquired at 3 Tesla. Cho concentrations of the tumors were analyzed by a frequency domain fit and then normalized to the corresponding contralateral healthy brain tissue. Metabolite images were used to determine the maximum and mean Cho concentrations of the tumor. Further, contrast-enhancement (CE) of the tumor was analyzed on standard MRI. All patients subsequently underwent tumor resection or stereotactic biopsy to confirm diagnosis of glioma.
Results: Histopathological examinations revealed gliomas in all patients (WHO °II: n=27; WHO °III: n=26; WHO °IV: n=10). There was a statistically significant difference in both normalized maximum and mean Cho between low-grade and high-grade gliomas (mean: 1.45±0.28 vs. 2.16±0.36, p<0.05; maximum: 1.64±0.32 vs. 3.32±0.55, p<0.0001). Receiver operating curve-analyses rendered a 2.02 cut-off value for maximum Cho with a sensitivity and specificity of 86.1% and 77.8%, respectively, to discriminate high-grade from low-grade tumors. For mean Cho, we found a corresponding cut-off value of 1.52 (sensitivity 77.8%, specificity 63.0%). The diagnostic accuracy of maximum Cho was superior to that of mean Cho (82.5% vs. 71.4%), but both were superior to CE of the tumor (61.9%). Adding the information of CE did not decisively improve accuracy of maximum or mean Cho.
Conclusions: Both, maximum and mean Cho differ between low and high-grade gliomas. CE is not reliable in distinguishing between high- and low-grade gliomas. Compared to mean Cho, maximum Cho of the tumor provides a far better accuracy in the discrimination of low- and high-grade tumors, indicating the usefulness of this single parameter in the process of therapeutic decision-making.