Reversed halo sign on high-resolution CT of cryptogenic organizing pneumonia: diagnostic implications.
OBJECTIVE
The aim of our study was to evaluate the usefulness of the reversed halo sign on high-resolution CT in the diagnosis of cryptogenic organizing pneumonia.


METHODS
Between 1996 and 2001, we saw 31 patients with biopsy-proven cryptogenic organizing pneumonia. During the same period, we also saw 30 patients with non-cryptogenic organizing pneumonia diseases, from which cryptogenic organizing pneumonia should be differentiated: Wegener's granulomatosis (n = 14), diffuse bronchioloalveolar carcinoma (n = 10), chronic eosinophilic pneumonia (n = 5), and Churg-Strauss syndrome (n = 1). Two independent observers analyzed CT findings and recorded how frequently the so-called reversed halo sign (central ground-glass opacity and surrounding air-space consolidation of crescentic and ring shape) was seen on high-resolution CT.


RESULTS
The most common patterns of parenchymal abnormalities of cryptogenic organizing pneumonia were ground-glass opacity (28/31 patients, 90%) and consolidation (27/31, 87%). The ground-glass opacity pattern showed random distribution, and the consolidation pattern showed subpleural or peribronchovascular (20/27 patients, 74%) distribution with predominance in the middle or lower lung zone. The reversed CT halo sign was seen in six (19%) of 31 patients with cryptogenic organizing pneumonia and in none of the patients with the diseases that needed to be differentiated from cryptogenic organizing pneumonia on CT.


CONCLUSIONS
The reversed halo sign, although seen only in one fifth of patients with the disease, appears relatively specific to make a diagnosis of cryptogenic organizing pneumonia on CT.
Kim
Sang Jin
SJ
Department of Diagnostic Radiology, Yonsei University College of Medicine, YongDong Severance Hospital, Seoul 135-270, Korea.
Lee
Kyung Soo
KS
Ryu
Young Hoon
YH
Yoon
Young Cheol
YC
Choe
Kyu Ok
KO
Kim
Tae Sung
TS
Sung
Ki Jun
KJ
D000328:Adult; D000368:Aged; D018549:Cryptogenic Organizing Pneumonia / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed