MET-PET/CT and MET-PET/MR fusion images with the Leksell GammaPlan®. Upper : MR-enhanced images; MR-enhanced volume (blue line), 1.26 cm³. Middle : MET-PET/CT fusion images; metabolic tumor volume (brown line), 1.41 cm³; matching percentage, 25.5%. Lower : MET-PET/MR fusion images; metabolic tumor volume, 1.41 cm³ (green line); matching percentage, 25.0%. Matching volume : MTV including the MR-enhanced volume; matching percentage (%) : (matching volume/total MTV)×100. MET-PET : 11C-methionine positron emission tomography, CT : computed tomography, MR : magnetic resonance, MTV : metabolic tumor volume.