Legend Ax T2W FLAIR: rounded high signal mass centered in the right caudate head. Ax T2W: More inferiorly, rounded mass in the right cerebellar hemisphere, with increased T2W signal peripherally and isointense signal centrally.

Legend Ax T1W: The caudate lesion is low signal on non-contrast T1W. Following gadolinium, the anteromedial portion of the caudate lesion enhances and the cerebellar lesion shows a thick rim of enhancement. Note the thin layer of enhancement along the ependyma of the lateral ventricles.

Legend Ax T1W: Following gadolinium, nodular enhancement is seen along the margins of the lateral ventricles.

Legend Proton Spectroscopy: Voxels over the caudate and cerebellar lesions show marked increase in lipid and lactate and moderate increase in choline compared to creatine. NAA is difficult to detect above the broad shoulder of glutamine/glutamates. Key words: mri mrs tumor neoplasia AIDS

Brain Diagnosis: CNS Lymphoma & AIDS