title: Cystic lung disease: a comparison of cystic size, as seen on expiratory and inspiratory HRCT scans.
abstract: OBJECTIVE
  To determine the effects of respiration on the size of lung cysts by comparing inspiratory and expiratory high-resolution CT (HRCT) scans.
  
  
  METHODS
  The authors evaluated the size of cystic lesions, as seen on paired inspiratory and expiratory HRCT scans, in 54 patients with Langerhans cell histiocytosis (n = 3), pulmonary lymphangiomyomatosis (n = 4), confluent centrilobular emphysema (n = 9), paraseptal emphysema and bullae (n = 16), cystic bronchiectasis (n = 13), and honeycombing (n = 9). Using paired inspiratory and expiratory HRCT scans obtained at the corresponding anatomic level, a total of 270 cystic lesions were selected simultaneously on the basis of five lesions per lung disease. Changes in lung cyst size observed during respiration were assessed by two radiologists. In a limited number of cases (n = 11), pathologic specimens were obtained by open lung biopsy or lobectomy.
  
  
  RESULTS
  All cystic lesions in patients with Langerhans cell histiocytosis, lymphangiomyomatosis, cystic bronchiectasis, honeycombing, and confluent centrilobular emphysema became smaller on expiration, but in two cases of paraseptal emphysema and bullae there was no change.
  
  
  CONCLUSIONS
  In cases in which expiratory CT scans indicate that cysts have become smaller, cystic lesions may communicate with the airways. To determine whether, for cysts and cystic lesions, this connection does in fact exist, paired inspiratory and expiratory HRCT scans are necessary.
authors.affiliation: Department of Diagnostic Radiology, Dong-A University College of Medicine, Pusan, Korea.
authors.forename: K N
authors.initials: KN
authors.lastname: Lee
authors.forename: S K
authors.initials: SK
authors.lastname: Yoon
authors.forename: S J
authors.initials: SJ
authors.lastname: Choi
authors.forename: J M
authors.initials: JM
authors.lastname: Goo
authors.forename: K J
authors.initials: KJ
authors.lastname: Nam
mesh_terms: D003560:Cysts / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods*