A 33-year-old nonsmoking man was admitted whit sudden unset of dyspnea



Doctor's Information

Name : Hamidreza
Family : Haghighatkhah
Affiliation :Radiology department,ShohadaTajrish Hospital,SBMU
Academic Degree : Associate professor of Radiology
Email : This email address is being protected from spambots. You need JavaScript enabled to view it.
Resident : Hadi Zolfeghari


Case Section

Chest Imaging


Patient's Information

Gender : Male
Age : 33


Clinical Summary

A 33-year-old nonsmoking man was admitted whit sudden unset of dyspnea. The patient also complained of pleuretic chest pain and malaise


Imaging Findings

CT image shows the reversed halo sign in the posterior segment of the right lower lobe. CT angiography shows a clot in the right lower lobe pulmonary segmental artery and its branches.


Differential Diagnosis

• cryptogenic organizing pneumonia (COP),
• invasive fungal infections (IFI)
• granulomatosis with polyangiitis (Wegener's granulomatosis)
• sarcoidosis
• pneumocystis pneumonia
• tuberculosis
• community-acquired pneumonia
• lymphomatoid granulomatosis
• lipoid pneumonitis
• pulmonary neoplasms
• pulmonary infarction


Final Diagnosis

reversed halo sign due to acute PE


Discussion (Related Text)

Reversed halo sign (RHS), also known as the atoll sign, is defined as central ground-glass opacity (GGO) surrounded by denser consolidation of crescentic (forming more than three fourths of a circle) or ring (forming a complete circle) shape of at least 2 mm in thickness. It was initially described on high-resolution CT.
The reversed halo sign was first described and is most commonly associated with COP but is not specific to this
disease.1 It has been reported in the setting of bacterial pneumonia, mucormycosis, paracoccidioidomycosis, tuberculosis,sarcoidosis, radiofrequency ablation, lymphomatoid granulomatosis, Wegener granulomatosis, tumor, and pulmonary infarcts.4–8 The reversed halo sign is seen in approximately 20% of patients with COP and 10% of cases of South American blastomycosis.1,4 Actual percentage of the reversed halo sign in the other listed conditions is not known but is likely seen in a small minority of patients. Though initially believed to be pathognomonic for organizing pneumonia, the reversed halo sign can be seen in multiple conditions. Recognition of this imaging finding in correlation with clinical parameters, travel history, and other radiographic findings is imperative to establish an accurate diagnosis.



1. Hansell DM, Bankier AA, MacMahon H, McLoud TC, Muller NL, Remy J. Fleischner Society: glossary of terms for thoracic imaging. Radiology 2008;246:697–722 [PubMed]
2. Zompatori M, Poletti V, Battista G, Diegoli M. Bronchiolitis obliterans with organizing pneumonia (BOOP), presenting as a ring-shaped opacity at HRCT (the atoll sign). A case report. Radiol Med 1999;97:308–10 [PubMed]
3. Marchiori E, Zanetti G, Irion KL et-al. Reversed halo sign in active pulmonary tuberculosis: criteria for differentiation from cryptogenic organizing pneumonia. AJR Am J Roentgenol. 2011;197 (6): 1324-7. doi:10.2214/AJR.11.6543 - Pubmed citation


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