Simultaneous assessment of airway instability and respiratory dynamics with low-dose 4D-CT in chronic obstructive pulmonary disease: a technical note

Respiration. 2014;87(4):294-300. doi: 10.1159/000357448. Epub 2014 Feb 14.


Background: Advanced-stage chronic obstructive pulmonary disease (COPD) is associated with severely altered respiratory dynamics. Dynamic airway instability is usually diagnosed by invasive bronchoscopy. Cine-computed tomography (CT) may be used alternatively, but is limited to predefined anatomical positions. Also, a paradoxical diaphragmatic motion has been described in patients with emphysema.

Objectives: As the airways and chest wall show inherently high contrast to airway lumen and lung tissue, low-dose CT acquisitions potentially suffice for depicting tracheobronchial and chest wall motion. Therefore, we propose low-dose dynamic respiratory-gated multidetector CT (4D-CT) of the whole chest as a new method to assess respiratory dynamics.

Methods: 4D-CT was performed in 3 patients (52, 62 and 76 years old) with suspected tracheal instability due to COPD or tracheal stenosis at minimal pitch (0.09) and radiation exposure (1.4-1.9 mSv) during regular tidal breathing registered by a belt system. Image reconstruction involved a raw data-based iterative algorithm (1.5-mm slice thickness, 1.0-mm z-axis increment, 5% respiratory increment), resulting in a stack of 6,700 images, which were evaluated with a 4D-viewing tool.

Results: An excessive dynamic collapse of the trachea in combination with tracheobronchomalacia (TBM) of the main-stem and segmental bronchi, and a paradoxical diaphragmatic motion were demonstrated in 1 case. Moreover, we detected a saber-sheath trachea and main-stem TBM in another case. The third case showed a fixed tracheal stenosis.

Conclusions: 4D-CT provides unprecedented z-axis coverage and time-resolved volumetric datasets of the whole chest. Airway instability, stenosis and paradoxical diaphragmatic motion may be assessed simultaneously, preceding interventions such as airway stabilization or lung volume reduction.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Diaphragm / diagnostic imaging
  • Diaphragm / physiopathology
  • Feasibility Studies
  • Four-Dimensional Computed Tomography
  • Humans
  • Male
  • Middle Aged
  • Multidetector Computed Tomography
  • Pulmonary Disease, Chronic Obstructive / diagnostic imaging*
  • Pulmonary Disease, Chronic Obstructive / physiopathology
  • Respiratory Mechanics*
  • Thoracic Wall / diagnostic imaging
  • Thoracic Wall / physiopathology
  • Trachea / diagnostic imaging*
  • Trachea / physiopathology