title: Pulmonary sarcoidosis. Correlation of expiratory high-resolution CT findings with inspiratory patterns and pulmonary function tests.
abstract: OBJECTIVE
  To assess the presence and extent of air trapping (AT) on chest high-resolution CT (HRCT) in sarcoidosis and to correlate such findings with patterns, lesion extent on inspiratory CT and pulmonary function tests (PFT).
  
  
  METHODS
  Thirty patients with sarcoidosis underwent inspiratory and expiratory HRCT and PFT. HRCT images were evaluated for presence, distribution and AT extent as well as the predominant HRCT pattern and the extent of lesions at inspiration. Attenuation difference in the AT regions at expiration and at inspiration were calculated. The presence and extent of AT were correlated with PFT, extent of involvement and predominant inspiratory patterns.
  
  
  RESULTS
  AT was present in 25/30 patients with no lung zone predilection. AT was the only CT indication of pulmonary sarcoidosis in 3/30 patients who also had normal PFT. Attenuation difference between inspiration and expiration ranged from -40 HU to 106 HU. In 2 patients, a paradoxical decrease of lung attenuation was observed at expiration. A significant correlation was found between AT extent at expiration, with residual volume-total lung capacity ratio and residual volume.
  
  
  CONCLUSIONS
  AT is an additional HRCT finding in sarcoidosis. AT may involve any lung zone, including costophrenic angles and may be the only CT feature of pulmonary sarcoidosis. Strong correlation is only found with PFT values that are specific for incomplete lung emptying at expiration.
authors.affiliation: Department of Radiology, University Hospital of Crete, Stavrakia, Heraklion, Crete, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Magkanas
authors.forename: A
authors.initials: A
authors.lastname: Voloudaki
authors.forename: D
authors.initials: D
authors.lastname: Bouros
authors.forename: P
authors.initials: P
authors.lastname: Prassopoulos
authors.forename: C
authors.initials: C
authors.lastname: Alexopoulou
authors.forename: N
authors.initials: N
authors.lastname: Tzanakis
authors.forename: M
authors.initials: M
authors.lastname: Linardakis
authors.forename: N
authors.initials: N
authors.lastname: Gourtsoyiannis
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012115:Residual Volume; D012119:Respiration; D012129:Respiratory Function Tests; D017565:Sarcoidosis, Pulmonary / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed; D014109:Total Lung Capacity