MRI can detect radiation necrosis in irradiated brain. Representative, transaxial, T2-weighted spin-echo images acquired longitudinally from non-Ab-treated, bevacizumab-treated, and B20-4.1.1-treated mice at 3 (top), 6 (middle) and 10 weeks (bottom) following a single 60 Gy at (50% isodose) of radiation. Slices are chosen to display the same anatomic region of the brain at all three time points.