Purpose: To determine whether the "halo sign" at computed tomography (CT) could be used to differentiate hemorrhagic from nonhemorrhagic pulmonary nodules.
Materials and methods: CT scans of 12 patients with hemorrhagic pulmonary nodules and of a control group of 10 patients with nonhemorrhagic pulmonary nodules were randomized and reviewed by two chest radiologists. Nodules were considered hemorrhagic if a surrounding halo of ground-glass attenuation was present.
Results: Nodules were correctly identified as either hemorrhagic or nonhemorrhagic by both observers in 19 of the 22 cases (86%). Eight of the 12 patients with hemorrhagic nodules had an infectious process including invasive aspergillosis, candidiasis, cytomegalovirus, herpes simplex virus, or coccidioidomycosis. Four of 12 patients with hemorrhagic nodules had a noninfectious cause including Wegener granulomatosis, metastatic angiosarcoma, and Kaposi sarcoma.
Conclusion: Most hemorrhagic pulmonary nodules have a characteristic CT appearance consisting of a central area of soft-tissue attenuation with a surrounding halo of ground-glass attenuation that allows distinction from nonhemorrhagic nodules.