Holly leaf sign - refers to the typical chest radiograph appearance of calcified pleural plaques. The well-defined but irregular thickened edges simulate the appearance of a holly leaf. ‘Geographic density’ is another common term used to describe their appearance. Pleural plaques are the most common form of asbestos related disease.
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Comet tail sign - a CT chest sign of round atelectasis. It consists of spiralling curvilinear opacities extending out to a subpleural “mass”. The rounded nature of the mass-like collapsed portion of lung causes the adjacent bronchovascular bundles to be pulled in resembling a comet tail. Round atelectasis is most commonly the result of asbestos related pleural disease.