Chest Imaging

Halo sign

an ill-defined pulmonary nodule surrounded by a circular margin of ground glass attenuation. Usually this sign represents oedema or haemorrhage. It has proved useful in the appropriate clinical setting as an early manifestation of invasive pulmonary aspergillosis (Fig.1). It must be emphasized, however, that the halo sign is nonspecific and may be seen in many other lesions in which blood vessels are compromised or nodules are surrounded by haemorrhage. The halo sign has been reported in patients with candidiasis pulmonary, cytomegalovirus CMV pneumonia and herpes simplex pneumonia, as well as in patients with Kaposis sarcoma and metastatic angiosarcoma.

PG

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Fig.1

CT scan in a patient with invasive pulmonary aspergillosis. The peripheral areas of consolidation are surrounded by a halo of ground-glass opacity.
Halo sign, Fig.1