Brain tumor volumes as assessed by magnetic resonance imaging (MRI) do not always spatially overlap with biological tumor volumes (BTV) measured by [^(18)F]Fluoroethyltyrosine positron emission tomography ([^(18)F]FET PET). We prospectively investigated volumetric patterns based on the extent of tumor volume overlap between the two modalities. Eighty-six patients with newly diagnosed glioma who had undergone MRI and [^(18)F]FET PET between 2007 and 2009 were included in this prospective …