Evaluation of cerebral glioma grade by using normal side creatine as an internal reference in multi-voxel 1H-MR spectroscopy.

PURPOSE Our purpose was to evaluate cerebral glioma grade by using normal side creatine (Cr) as an internal reference in multi-voxel 1H-MR spectroscopy. MATERIALS AND METHODS We examined 25 adult patients with glial brain tumors. Ratios of maximum Cho/Cr (normal) (max- Cho/Cr(n)) and minimum NAA/Cr(normal) (min-NAA/ Cr(n)) were determined using Cr levels in the normal parenchyma. In addition, maximum Cho/Cr (max- Cho/Cr) and minimum NAA/Cr (min-NAA/Cr) were calculated from spectrum in the tumor areas. Tumors were graded according to metabolite ratios and the findings were compared to histopathological test results. The sensitivity, specificity, positive and negative predictive values of metabolite ratios were determined. RESULTS The ratio of max-Cho/Cr(n) was lower than that of max-Cho/Cr in the high-grade group (P = 0.001). Min-NAA/Cr(n), min-NAA/Cr, and max-Cho/Cr ratios demonstrated statistically significant differences between high-grade (n = 19) and low-grade tumors (n = 6). The min-NAA/Cr and min-NAA/Cr(n) ratios were inversely correlated with tumor grade (P = 0.027 and P = 0.009, respectively). CONCLUSION Use of normal side Cr as an internal reference provides a more objective evaluation for brain tumor grading. Our data showed that Cr tended to be low in the high-grade tumors. In addition to conventional metabolite ratios, the Min-NAA/Cr(n) ratio might be useful in brain tumor grading. Combined use of metabolite ratios might be helpful in grading brain tumors in cases without significantly increased Cho/Cr ratios.