Dynamic airway evaluation with volume CT: initial experience

The purpose of the study was to prospectively establish the use of a novel multidetector computed tomography unit (MDCT) with 320 x 0.5 detector rows for the evaluation of tracheomalacia by using a dynamic expiratory low-dose technique.

Six adult patients (5 men, 1 woman; mean age, 53.7 years [37-70 years]) referred for a clinical suspicion of tracheomalacia were studied on a 320-row MDCT unit by using the following parameters: 120 kVp, 40-50 mA, 0.5-second gantry rotation, and z-axis coverage of 160 mm sufficient to cover the thoracic trachea to the proximal bronchi. Image acquisition occurred during a forceful exhalation. The image data set was subject to the following analyses: cross-sectional area of airway lumen at 4 predefined locations (thoracic inlet, aortic arch, carina, and bronchus intermedius) and measurement of airway volume.

All 6 patients had evidence of tracheomalacia, the proximal trachea collapsed at a later phase of expiration (3-4 seconds) than the distal trachea (2-3 seconds). The most common region of airway collapse occurred at the level of the aortic arch (5/6 [83%]), Three patients (50%) had diffuse segmental luminal narrowing that involved the tracheobronchial tree. The radiation dose (estimated dose length product, computed tomography console) measured 293.9 mGy in 1 subject and 483.5 mGy in 5 patients.

Four-dimensional true isophasic and isovolumetric imaging of the central airways by using 320-row MDCT is a viable technique for the diagnosis of tracheomalacia; it provides a comprehensive assessment of airways dynamic.