PET Imaging in Gliomas: Clinical Principles and Synergies with MRI

Brain tumors can potentially arise in any anatomical regions of the central nervous system (CNS), with the vast majority occurring in the brain and the remainder occurring in the meninges, spinal cord, and cranial nerves. Gliomas are tumors of neuroectodermal origin arising from glial or precursor cells; they constitute more than 80% of CNS primary tumors in adults, including astrocytomas, oligodendrogliomas, and ependymomas. According to the 2016 WHO update, WHO grade II and III gliomas are largely dichotomized into astrocytomas or oligodendrogliomas based on molecular/genetic factors, with the previous classification of oligoastrocytoma being appropriate only in very unusual circumstances. Glioblastoma is the most aggressive and common of all CNS tumors, representing approximately 50–60% of all gliomas. The obvious need of synergy between magnetic resonance imaging (MRI) and positron-emitting tomography (PET) in brain tumors has provided the grounds to develop simultaneous PET/MRI, to improve patient compliance and workflow.