DIRECT COMPARISON BETWEEN DIFFUSION-WEIGHTED MRI AND PET/CT WITH [11С]METHIONINE IN PATIENTS WITH CEREBRAL GLIOMAS

Abstract

The aim of the study was to assess the diagnostic value of MR diffusion imaging (DWI) and hybrid positron emission and computed tomography (PET/CT) with [11C]methionine for glioma grading and to compare the spatial distribution of diffusion restriction and [11C]methionine uptake abnormalities within a tumor.Material and methods: MRI with diffusion sequences and PET/CT with [11C]methionine were performed for 46 patients with untreated histologically proven brain gliomas. Quantitative evaluation included the minimal apparent diffusion coefficient value (ADCmin) in the tumor and maximum [11C]methionine uptake ratio, measured as ratio of highest tumor count density to that of the brain cortex(tumor-to-cortex-T/Cmax). Mean measurements of ADC (ADCmean) and T/C (T/Cmean) were obtained for each tumor. The ADC and T/Cratio values for glioma grading were assessed and correlations were evaluated. In addition PET and ADC images were coregistered to each other.Results: The T/Cmax and ADCmin values were significantly negatively correlated (r=–0,82). The T/Cmean and ADCmean measurements also demonstrated the significant negative correlation (r=0,56). The T/Cmax showed best accuracy in glioma grading. Sites of maximal radiotracer uptake and minimal ADC did not match in 34% of cases and in 66% of tumors the match was partial.Conclusion: Diagnostic accuracy of PET/CT using [11C]methionine in glioma grading exceeds DWI-MRI, and for both methods it is preferable to analyze a small tumor volume. The T/C ratios and ADC measurements demonstrate the significant inverse correlations. High rate of mismatch between spatial distribution of increased [11C]methionine uptake and low ADC areas within a tumor could be a result of different biological features registered by PET and DWI.