Radiation necrosis on MRI and perfusion MRI

This 63-year-old patient with non-small cell lung cancer and solitary brain metastasis was treated with surgery followed by adjuvant fractionated stereotatic radiation therapy. Additional treatments included chemoradiotherapy to the lung primary tumor followed by immunotherapy. She developed symptomatic radiation necrosis 18 months after stereotatic radiation therapy. She was treated with steroids without relief and ultimately underwent surgery, which confirmed the diagnosis of radiation necrosis. (A) T1 post-contrast sequence with typical “cut green pepper” ring enhancement. (B) ADC is typically elevated in the area of radiation necrosis. (C) Perfusion MRI typically shows decreased relative cerebral blood volume in the area of radiation necrosis. (Contributed by Dr. Puyao Li.)