Correlation of 11C-methionine PET and diffusion-weighted MRI

Abstract

11C-Methionine (MET) PET and diffusion-weighted (DW) MRI are commonly used for evaluation of gliomas. We assessed the correlation between MET uptake and diffusion restriction measured on DW MRI in glioma. Thirty-one patients with gliomas, who were initially examined with MET PET and DW MRI, were enrolled retrospectively. MET PET and apparent diffusion coefficient (ADC) images were coregistered to each other, using rigid-body transformation. Tumor-to-normal count density ratio of the cortex (TNR) and normalized apparent diffusion coefficient (nADC) value were measured for each voxel on the MET PET and ADC map. The maximum TNR (TNRmax) and minimum nADC (nADCmin) were obtained for each tumor. Correlations between those parameters were evaluated. The TNRmax and nADCmin values of a glioma were significantly correlated (r=-0.42). TNRmax and nADCmin were significantly correlated with glioma grades. Furthermore, TNRmax and nADCmin showed a trend for correlation with the Ki-67 index. We analyzed the correlation between voxel-based TNR and ADC within a tumor and observed no correlation between them. Regions with high MET uptake did not correspond with regions with low nADC. We found a negative correlation between TNRmax and nADCmin for each glioma; however, MET uptake and ADC within a tumor were independent of each other and were heterogeneous. The two parameters represent different biological features; thus, as a comprehensive approach, MET PET and DW MRI might have a complementary role in the characterization of gliomas.