Non-invasive assessment of heterogeneity of gliomas using diffusion and perfusion MRI: correlation with spatially co-registered PET

Background Heterogeneity of gliomas challenges the neuronavigated biopsy and oncological therapy. Diffusion and perfusion magnetic resonance imaging (MRI) can reveal the cellular and hemodynamic heterogeneity of tumors. Integrated positron emission tomography (PET)/MRI is expected to be a non-invasive imaging approach to characterizing glioma. Purpose To evaluate the value of apparent diffusion coefficient (ADC), cerebral blood volume (CBV), and spatially co-registered maximal standard uptake value (SUVmax) for tissue characterization and glioma grading. Material and Methods Thirty-seven consecutive patients with pathologically confirmed gliomas were retrospectively investigated. The relative minimum ADC (rADC(min)), relative maximal ADC (rADC(max)), relative maximal rCBV (rCBV(max)), the relative minimum rCBV (rCBV(min)), and the corresponding relative SUVmax (rSUV(max)) were measured. The paired t-test was used to compare the quantitative parameters between different regions to clarify tumor heterogeneity. Imaging parameters between WHO grade IV and grade II/III gliomas were compared by t-test. The diagnostic efficiency of multiparametric PET/MRI was analyzed by receiver operating characteristic (ROC) curve. Results The values of rSUV(max) were significantly different between maximal diffusion/perfusion area and minimum diffusion/perfusion area (P < 0.001/P < 0.001) within tumor. The values of rADC(min) (P < 0.001), rCBV(max) (P = 0.002), and corresponding rSUV(max) (P = 0.001/P < 0.001) could be used for grading gliomas. The areas under the ROC curves of rSUV(max) defined by rADC(min) and rCBV(max) were 0.89 and 0.91, respectively. Conclusion Diffusion and perfusion MRI can detect glioma heterogeneity with excellent molecular imaging correlations. Regions with rCBV(max) suggest tissues with the highest metabolism and malignancy for guiding glioma grading and tissue sampling.