Background: Magnetic resonance spectroscopic imaging (MRSI) can provide spatially encoded metabolite information and improve tissue specificity in human brains. The major goal of this study was to evaluate the correlation of metabolite ratios measured by MRSI with histopathological grading of cerebral gliomas.
Methods: Twenty-seven patients with cerebral gliomas were referred consecutively for pre-surgical evaluation. The lesions included 10 grade II, 5 grade III, and 12 grade IV gliomas. MRSI data were acquired during the same session of conventional magnetic resonance imaging and analyzed in terms of N-acetylaspartate (NAA), creatine-phosphocreatine (Cr), choline-containing compounds (Cho), and lactate.
Results: There were significantly lower NAA/Cr and higher Cho/Cr, Cho/NAA and (Cho+Cr)/NAA ratios (ps < 0.001) in gliomas than in normal tissues. There were significantly lower NAA/Cr and higher Cho/NAA and (Cho+Cr)/NAA ratios (ps < or = 0.05) in World Health Organization (WHO) grade III or IV gliomas than in grade II gliomas. A significant correlation was identified between the (Cho+Cr)/NAA ratio and WHO grade (p < 0.05). There was no significant metabolite difference between grade III and grade IV tumors (ps > 0.1), or significant difference in lactate occurrence rates among different grades (p = 0.26).
Conclusions: Proton MRSI can provide in vivo information about the metabolic status of cerebral gliomas, and the (Cho+Cr)/NAA ratio can discriminate different grades better than other metabolite ratios. However, substantial overlap of metabolite ratios among different severities of malignancy makes it impossible to confirm the WHO grade of a specific cerebral glioma by using clinical MRSI.