ARRS Case of the Week
CHEST IMAGING: Airways Disease
Case Author: Jonathan H. Chung, MD, National Jewish Health
49-year-old woman with cough and shortness of breath; high-resolution chest CT has been performed, and the next imaging step must be determined.
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Inspiratory high-resolution CT image in lung window shows normal morphologic features of the trachea and mediastinal structures. Results of pulmonary function tests showed an obstructive pattern with a normal inspiratory curve but a truncated expiratory limb (not shown).
Dynamic expiratory CT
Dynamic expiratory CT is the most sensitive means of detecting tracheobronchomalacia (TBM). Static end-expiratory CT may show significant collapse of the large airways, but may miss cases of TBM obvious on dynamic expiratory imaging.
Static inspiratory CT is usually not useful in the evaluation of TBM. However, a lunate trachea (large coronal tracheal diameter relative to sagittal tracheal diameter) suggests the presence of TBM, which should be correlated with dynamic expiratory CT or bronchoscopy findings.
Classically, a greater than 50% decrease in cross-sectional tracheal diameter during expiration was used as a cutoff for TBM. However, recent data have shown that a greater than 50% decrease in crosssectional tracheal diameter is common in healthy persons. A more rigorous threshold (> 70%) for diagnosing TBM will likely be necessary.
Chung JH, Kanne JP, Gilman MD. CT of diffuse tracheal diseases. AJR 2011; 196:486; [web]W240–W246
Ridge CA, O'Donnell CR, Lee EY, Majid A, Boiselle PM. Tracheobronchomalacia: current concepts and controversies. J Thorac Imaging 2011; 26:278–289
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