Simultaneous mapping of vasculature, hypoxia and proliferation using DSC-MRI, 18F-FMISO PET, and 18F-FLT PET in relation to contrast enhancement in newly diagnosed glioblastoma
Résumé
Conventional MRI plays a key role in the management of patients with high grade glioma but multiparametric MRI and PET tracers could provide further information to better characterize the tumor metabolism and heterogeneity, by identifying the regions having a high risk of recurrence. In this study, we focused on the proliferation, hypervascularization and hypoxia, all factors considered as factors of poor prognosis. They were assessed by measuring the uptake of 18F-FLT, the rCBV maps and the uptake of 18F-FMISO, respectively. For each modality, the volumes and high uptake sub-volumes (hotspots) were semi-automatically segmented and compared to contrast enhancement (CE) volume on T1w-Gd images, commonly used in the management of patient with glioblastoma. Methods: DSC MRI (31 patients), 18F-FLT PET (20 patients) and/or 18F-FMISO PET (20 patients), for a total of 31 patients, were performed on pre-operative glioblastoma patients. Volumes and hotspots were segmented on SUV maps for 18F-FLT (using FLAB) and 18F-FMISO (using mean contralateral + 3.3 SD) PET and on rCBV maps (using mean contralateral + 1.96 SD) for DSC MRI and overlaid on T1w-Gd images. For each modality, the percentage of peripheral volumes and the peripheral hotspot outside the CE volume were calculated. Results: All tumors showed high proliferation, hypervascularization and hypoxic regions. Images also showed pronounced heterogeneity of both tracers uptake and rCBV maps, within each individual case. Overlaid volumes on T1w-Gd images showed that some proliferative, hypervascularization and hypoxic regions extended beyond the CE volume but with marked differences between patients. The ranges of peripheral volume outside the CE volume were [1.6% - 155.5 %], [1.5% - 89.5%] and [3.1% - 78.0%] for 18F-FLT, rCBV and 18F-FMISO respectively. All patients had hyperproliferative hotspots outside CE volume, whereas hotspots of hypervasculature and hypoxia were mainly detected within the enhancing region. Conclusion: The spatial analysis of the multiparametric maps with the segmented volumes and hotspots provides valuable information to optimize the management and treatment of the patients with glioblastoma.
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