In radiology, the halo sign is a finding on ultrasound that suggests the diagnosis of temporal arteritis.[1] The standard diagnostic test for temporal arteritis is biopsy; however, ultrasound and MRI show promise for replacing it.[2]
The halo sign of temporal arteritis should not be confused with Deuel's halo sign, which is a sign of fetal death.[3]
The halo sign is also understood as a region of ground-glass attenuation surrounding a pulmonary nodule on an X-ray computed tomography (CT scan) of the chest. It can be associated with hemorrhagic nodules, tumors, or inflammatory processes, but is most commonly known as an early radiographic sign of invasive pulmonary infection by the fungus species Aspergillus.