Atoll (illustration)

Case contributed by Mohammad Salem Amer
Diagnosis not applicable
Diagram

Image generated with Bing.com by Mohammad Salem Amer.

Case Discussion

The atoll sign in hepatic imaging has been characterized as a liver lesion with a peripheral rim of high T2 signal intensity and a core that appears isointense to the background of non-cirrhotic liver on T2WI, like an atoll. It is regarded a defining feature of an inflammatory hepatic adenoma, yet it occurs in only around one-third of cases.

In chest imaging the atoll sign, also known as the reversed halo sign, is a focal ground-glass opacity surrounded by a ring of consolidation that might be complete or incomplete. The symptom was first identified in organizing pneumonia, although it can also appear in infections, infarctions, granulomatous disease, inflammation, and tumors.

Image generated with Bing.com by Mohammad Salem Amer.

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