Figure 3.

Radiation necrosis in an 86-year-old man after radiation therapy for high-grade glioma. A) Axial contrast-enhanced fat-saturated T1-weighted MR image shows an irregular enhancing mass in the left parietal lobe. B) DSC perfusion MR image shows low rCBV in the lesion (arrow). C) Fused PET-CT with 2-[fluorine-18] fluoro-2-deoxy-D-glucose shows focal decreased glucose metabolism in the lesion (arrow). PET-CT is an additional imaging modality in the radiologist's armamentarium, but the definitiveness of differentiating necrosis or recurrent tumor is not always straightforward.