title: The spectrum of presentations of cryptogenic organizing pneumonia in high resolution computed tomography.
abstract: BACKGROUND
  Various radiologic patterns of cryptogenic organizing pneumonia (COP) in X-rays have been reported for more than 20 years, and later, in computed tomography scans. The aim of the present study was to describe the spectrum of radiologic findings on high resolution computed tomography (HRCT) scans in patients with COP.
  
  
  METHODS
  HRCT scans of 31 sequential patients (mean age: 54.3±11 years; 55% male) with biopsy-proven COP in a tertiary lung center between 2009 and 2012 were reviewed by two experienced pulmonary radiologists with almost perfect interobserver agreement (kappa=0.83). Chest HRCTs from the lung apex to the base were performed using a 16-slice multi-detector CT scanner.
  
  
  RESULTS
  The most common HRCT presentation of COP was ground-glass opacity (GGO) in 83.9% of cases, followed by consolidation in 71%. Both findings were mostly asymmetric bilateral and multifocal. Other common findings were the reverse halo (48.4%), parenchymal bands (54.8%) and subpleural bands (32.3%). Pulmonary nodules were found in about one-third of patients and were frequently smaller than 5 mm in diameter. Both GGOs and consolidations were revealed more often in the lower lobes.
  
  
  CONCLUSIONS
  The main presentations of COP on HRCT include bilateral GGOs and consolidations in the lower lobes together with the reverse halo sign.
authors.affiliation: Chronic Respiratory Disaeses Research Center, National Research Institute of Tuberculosis and Lung Disease, Masih-e-Daneshvari Hospital, Shahid Beheshti Medical University, Tehran, Iran.
authors.forename: Payam
authors.initials: P
authors.lastname: Mehrian
authors.affiliation: Department of Radiology, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Makhtoom
authors.initials: M
authors.lastname: Shahnazi
authors.affiliation: Chronic Respiratory Disaeses Research Center, National Research Institute of Tuberculosis and Lung Disease, Masih-e-Daneshvari Hospital, Shahid Beheshti Medical University, Tehran, Iran ; Department of Radiology, Masih-e-Daneshvari Hospital, Shahid Beheshti Medical University, Tehran, Iran.
authors.forename: Ali Ahmadi
authors.initials: AA
authors.lastname: Dahaj
authors.affiliation: Department of Pathology, Masih-e-Daneshvari Hospital, Shahid Beheshti Medical University, Tehran, Iran.
authors.forename: Sorour
authors.initials: S
authors.lastname: Bizhanzadeh
authors.affiliation: Chronic Respiratory Disaeses Research Center, National Research Institute of Tuberculosis and Lung Disease, Masih-e-Daneshvari Hospital, Shahid Beheshti Medical University, Tehran, Iran ; Department of Radiology, Masih-e-Daneshvari Hospital, Shahid Beheshti Medical University, Tehran, Iran.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Karimi
keywords: Cryptogenic Organizing Pneumonia; Multidetector Computed Tomography; Pneumonia