Korean J Radiol.  2006 Sep;7(3):173-179. 10.3348/kjr.2006.7.3.173.

CT Analysis of the Anterior Mediastinum in Idiopathic Pulmonary Fibrosis and Nonspecific Interstitial Pneumonia

• Lee CH
• Lee HJ
• Son KR
• Chun EJ
• Lim KY
• Goo JM
• Im JG
• Heo JN
• Song JW

• KMID: 1114349
• DOI: http://doi.org/10.3348/kjr.2006.7.3.173

Abstract

OBJECTIVE
We wanted to determine whether the amount and shape of the anterior mediastinal fat in the patients suffering with usual interstitial pneumonia (UIP) or nonspecific interstitial pneumonia (NSIP) was different from those of the normal control group. MATERIALS AND METHODS: We selected patients who suffered with UIP (n = 26) and NSIP (n = 26) who had undergone CT scans. Twenty-six controls were selected from individuals with normal CT findings and normal pulmonary function tests. All three groups (n = 78) were individually matched for age and gender. The amounts of anterior mediastinal fat, and the retrosternal anteroposterior (AP) and transverse dimensions of the anterior mediastinal fat were compared by one-way analysis of variance and Bonferroni's test. The shapes of the anterior mediastinum were compared using the Chi-square test. Exact logistic regression analysis and polychotomous logistic regression analysis were employed to assess whether the patients with NSIP or UIP had a tendency to show a convex shape of their anterior mediastinal fat. RESULTS: The amount of anterior mediastinal fat was not different among the three groups (p = 0.175). For the UIP patients, the retrosternal AP dimension of the anterior mediastinal fat was shorter (p = 0.037) and the transverse dimension of the anterior mediastinal fat was longer (p = 0.001) than those of the normal control group. For the NSIP patients, only the transverse dimension was significantly longer than those of the normal control group (p < 0.001). The convex shape of the anterior mediastinum was predictive of NSIP (OR = 19.7, CI 3.32-infinity, p < 0.001) and UIP (OR = 24.42, CI 4.06-infinity, p < 0.001). CONCLUSION: For UIP patients, the retrosternal AP and transverse dimensions are different from those of normal individuals, whereas the amounts of anterior mediastinal fat are similar. UIP and NSIP patients have a tendency to have a convex shape of their anterior mediastinal fat.

Keyword

Thorax, CT; Lung, interstitial disease; Mediastinum

MeSH Terms

Tomography, X-Ray Computed/*methods
Radiographic Image Interpretation, Computer-Assisted/*methods
Pulmonary Fibrosis/*radiography
Middle Aged
Mediastinal Diseases/*radiography
Male
Lung Diseases, Interstitial/*radiography
Humans
*Body Composition
Aged
Adult
Adipose Tissue/*radiography

Figure

• 

  Fig. 1 The method of measurement for the amount and the anteroposterior and transverse dimensions of the anterior mediastinal fat. A. The amount of anterior mediastinal fat was quantified at the level of the aortic arch with software (Rapidia; 3DMED, Seoul, Korea). This software automatically calculated the areas of the anterior mediastinal fat having the attenuation range -190 to -50 HUs when the region of interest was drawn. B. The anteroposterior and transverse dimensions of the anterior mediastinal fat were measured at the level of the pulmonary trunk.

• 

  Fig. 2 The shapes of anterior mediastinal fat in the usual interstitial pneumonia, nonspecific interstitial pneumonia and normal control groups. A, B. The concave shape of the anterior mediastinum in the normal controls. C, D. The flat shape of the anterior mediastinum in the nonspecific interstitial pneumonia group. E, F. The convex shape of the anterior mediastinum in the usual interstitial pneumonia group.

• 

  Fig. 3 A hypothetical mechanism for the morphologic change in the anterior mediastinum due to pulmonary fibrosis in the usual interstitial pneumonia and nonspecific interstitial pneumonia patients. The widening of the transverse dimension and the shortening of the anteroposterior dimension of the anterior mediastinal fat seem to be caused by bilateral tensile forces induced by subpleural fibrosis of the lung tissue that was adjacent to the mediastinum.

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