Fig. 4From: Chest imaging using signs, symbols, and naturalistic images: a practical guide for radiologists and non-radiologistsAtoll sign. The so called “atoll sign” (white arrow) is represented by a central ground glass area bordered by a peripheral consolidation. This CT finding—similar to the oceanic atoll—is frequently observed in patients with COP; it has been also called “reversed halo sign”Back to article page