![](https://prod-images-static.radiopaedia.org/images/62370203/73c21eccaea17114d2f610a1c514879ab7936557efe4c80f0890316f972cf03b_big_gallery.jpeg)
This annotated T2 axial image through a tuberculoma nicely demonstrates a dual rim sign.
The outer low-signal rim is believed to be due to paramagnetic free radical production by macrophages in the abscess capsule whereas the high-signal inner rim, deep to the enhancing capsule, correlates microscopically with granulation tissue.
When seen this clearly and continuously surrounding a centrally necrotic lesion, it is strongly suggestive of an abscess rather than a tumor. In this instance the presence of low T2 signal central caseating necrotic material allows the high inner rim to be seen very well.
Case courtesy of Ammar Ashraf, Radiopaedia.org, rID: 79483