title: Paratracheal air cysts on thoracic multidetector CT: incidence, morphological characteristics and relevance to pulmonary emphysema.
abstract: OBJECTIVE
  To determine the incidence, morphological characteristics and relevance of paratracheal air cysts (PTACs) with pulmonary emphysema, as seen on thoracic multidetector CT (MDCT).
  
  
  METHODS
  The CT images of 854 consecutive patients who underwent thoracic MDCT during a period of 2 months at our institution were reviewed. 538 of the patients were male and 316 were female. The incidence, size and shape of the PTACs and their relation to pulmonary emphysema were retrospectively analysed.
  
  
  RESULTS
  Among the 854 patients, 69 (8.1%) had PTACs. 37 (6.9%) of the 538 male patients and 32 (10.1%) of the 316 female patients had PTACs. The highest prevalence of PTACs (25 patients, 11.2%) was found in those who were in the sixth decade of life. 48 (69.6%) PTACs measured 3-10 mm at the longest diameter and 33 (47.8%) were elongated on the coronal section images. 12 (17.4%) patients with PTACs had underlying gross morphological emphysema. The relationship between the presence of PTACs and the presence of emphysema and the relationship between the presence of PTACs and the severity of emphysema were not statistically significant. The size of PTACs showed an inverse relation to the severity of emphysema.
  
  
  CONCLUSIONS
  The incidence of PTACs was estimated to be much higher than that of previous studies. There was a slight female predilection for PTACs, most commonly found in the sixth decade of life; PTACs mostly measured 3-10 mm and were elongated in shape. The relation of PTACs to gross morphological emphysema was low.
  
  
  CONCLUSIONS
  PTACs are not correlated with the presence of emphysema on MDCT.
authors.affiliation: Department of Radiology, Korea University College of Medicine, Seoul, Republic of Korea.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Bae
authors.forename: E-Y
authors.initials: EY
authors.lastname: Kang
authors.forename: H S
authors.initials: HS
authors.lastname: Yong
authors.forename: Y K
authors.initials: YK
authors.lastname: Kim
authors.forename: O H
authors.initials: OH
authors.lastname: Woo
authors.forename: Y-W
authors.initials: YW
authors.lastname: Oh
authors.forename: K W
authors.initials: KW
authors.lastname: Doo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008476:Mediastinal Cyst / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D013902:Radiography, Thoracic / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D056910:Republic of Korea / Q000453:epidemiology; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D055815:Young Adult