|R||Radiation necrosis||Often incomplete C-shaped ring|
|M||Metastases||Thick, nodular wall|
|A||Abscess||Marked restriction on DWI; thin wall|
|G||Glioma||Thick, irregular wall if GBM|
Some people add L to the end of the mnemonic for lymphoma as well. Another entity to keep in mind, especially in certain patient populations, is neurocysticercosis, especially if there are other calcified lesions present.