MRI enhancement mechanism: local BBB destruction, microvascular rupture, I/R injury, granulation tissue proliferation, etc.; generally, the enhancement starts on the 3rd day after surgery, peaks at 2-3W, and disappears at 1M. Postoperative tumor residual or recurrence: tumor is not completely removed; MRI enhancement is reviewed within 1-3 days after surgery or after 1-2M, if there is nodular enhancement, it is mostly tumor residual or recurrence. Radiation encephalopathy: Early late-response phase: within 3M; mostly shows radioactive edema. Late late-response period: months or even years later; mostly manifesting as radiation necrosis, etc.