FIG 2. Brain MR imaging. A, Sagittal T1-weighted image shows the extent of the large mass, which is mostly isointense to gray matter with a mildly hyperintense perimeter. B, Axial T2-weighted image demonstrates the hypointense wall of the mass with surrounding brain edema. Thin, interrupted, low signal intensity zones (arrows) line the margin between the outer wall and central hyperintense necrotic area. C, Axial contrast-enhanced study reveals a thick, irregular enhancing rim. The low signal intensity zones (arrows) do not enhance.