Virtual Bronchoscopy and Other Three-Dimensional Imaging Methods

Abstract

Flexible bronchoscopy (FB) is the only method that permits real-time direct visualization and dynamic evaluation of the tracheobronchial system. Multidetector computed tomography (MDCT) scanners can generate accurate 2-dimensional (multiplanar reformation) and 3-dimensional (multiplanar volume reconstruction, external volume rendering, VR, and virtual bronchoscopy, VB) images of the airways. Patient breath-holding in suspended inspiration is important but with the new faster scanners volume coverage during quiet breathing can achieve high-quality images. The new imaging techniques offer distinct advantages over FB that include: accurate mapping of airway compression or stenosis, visualization of the airway beyond the area of obstruction, evaluation of smaller airways, and imaging of parenchymal and mediastinal abnormalities. External VR and VB can delineate congenital defects such as pulmonary underdevelopment spectrum, tracheobronchial branching anomalies, tracheo-oesophageal fistula, sequestration spectrum and vascular rings. High-resolution CT is used to evaluate bronchiectasis and air-trapping due to small-airway disease. Newer-generation MDCT scanners can be used to assess dynamic collapse of the airways. Radiation exposure remains a concern in CT; patient- and disease-specific dose reduction should be implemented according to the ALARA (‘as low as reasonably achievable’) principle. Alternative techniques such as magnetic resonance imaging should be considered.