Reverse halo sign

Reversed halo sign in active pulmonary tuberculosis

“…Most frequently associated with cryptogenic organising pneumonia (COP), this sign has been reported in a number of conditions like invasive pulmonary fungal infections, pneumocystis pneumonia, TB, lymphomatoid granulomatosis, granulomatosis with polyangitis, sarcoidosis, pulmonary neoplasm's and infarction, and following radiation therapy/radiofrequency ablation of lung malignancies 1. Presence of nodular walls and presence of nodules inside the halo is an important finding differentiating TB from COP, as was seen in our patient 2…”

Pulmonary infarction in acute pulmonary embolism: reversed halo sign

“…RHS denotes a focal, rounded area of ground-glass opacity surrounded by a complete or nearly complete ring of consolidation on high-resolution CT thorax examination as was seen in our patient 1. Previously considered to be specific for cryptogenic organising pneumonia, the sign has been described in a wide variety of infectious and non-infectious conditions such as pulmonary fungal infections, pulmonary infarction, granulomatosis with polyangitis, tuberculosis, sarcoidosis, pneumocystis pneumonia, etc 2.…”

Diffuse reversed halo sign in an immunocompetent patient

“…Later on, it was also observed among some immunocompetent patients with infectious pneumonia, such as tuberculosis or other bacterial and fungal infections [ [9] , [10] , [11] ]. It was also reported in several inflammatory conditions like sarcoidosis, pulmonary neoplasms, and after radiotherapy [ 12 ]. Marchiori et al proposed several radiological criteria to distinguish between these conditions.…”