Halo sign

The Halo sign refers to a radiological finding characterized by a ring-like appearance surrounding a central area of low attenuation, typically seen on CT scans. It is clinically significant as it often indicates the presence of a fungal infection, such as aspergillosis, particularly in immunocompromised patients. Recognising the Halo sign is crucial for timely diagnosis and management, as untreated fungal infections can lead to severe complications, including respiratory failure.