Fig. 1

MRI shows a well-circumscribed, lobulated mass in the left lateral ventricle trigone, with marked perilesional brain edema. A On the axial T1WI, the lesion displays low to intermediate signal intensity compared to that of the gray matter. B On the axial T2WI, the tumor displays heterogeneous high signal intensity with a few hypointense areas, and a low signal ring surrounding the neoplasm (arrows). C On the axial FLAIR, the lesion shows heterogeneous hyperintensity. D On the axial contrast-enhanced MRI, the tumor demonstrates significant enhancement and appears with the halo sign, the distinctive halo (red arrows) shows relatively weak enhancement compare to that of the mass (black arrows). E On the sagittal contrast-enhanced MRI, the lateral ventricular wall showed enhancement (red arrows). F On the corresponding color CBV image, the tumor shows decreased perfusion