Section Editor: Sandy Cheng-Yu Chen, M.D.
Taipei Medical University Hospital, Taipei, Taiwan
Cerebral toxoplasmosis and lymphoma are the 2 most common ring-enhancing lesions found in patients with HIV/AIDs. Toxoplasmosis typically presents as multiple ring-enhancing lesions with an eccentric enhancing nodule, also known as the target sign (B, arrows). Lesions most commonly occur in the basal ganglia and thalami and result in significant surrounding vasogenic edema (A). Hemorrhage can occur within the lesions, resulting in susceptibility on T2* sequences (C, arrow). Lymphoma, on the other hand, is more likely to be a solitary ring-enhancing periventricular lesion with ependymal spread.